kernel/fork.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/kernel/fork.c
   4  *
   5  *  Copyright (C) 1991, 1992  Linus Torvalds
   6  */
   7
   8 /*
   9  *  'fork.c' contains the help-routines for the 'fork' system call
  10  * (see also entry.S and others).
  11  * Fork is rather simple, once you get the hang of it, but the memory
  12  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
  13  */
  14
  15 #include <linux/anon_inodes.h>
  16 #include <linux/slab.h>
  17 #include <linux/sched/autogroup.h>
  18 #include <linux/sched/mm.h>
  19 #include <linux/sched/coredump.h>
  20 #include <linux/sched/user.h>
  21 #include <linux/sched/numa_balancing.h>
  22 #include <linux/sched/stat.h>
  23 #include <linux/sched/task.h>
  24 #include <linux/sched/task_stack.h>
  25 #include <linux/sched/cputime.h>
  26 #include <linux/seq_file.h>
  27 #include <linux/rtmutex.h>
  28 #include <linux/init.h>
  29 #include <linux/unistd.h>
  30 #include <linux/module.h>
  31 #include <linux/vmalloc.h>
  32 #include <linux/completion.h>
  33 #include <linux/personality.h>
  34 #include <linux/mempolicy.h>
  35 #include <linux/sem.h>
  36 #include <linux/file.h>
  37 #include <linux/fdtable.h>
  38 #include <linux/iocontext.h>
  39 #include <linux/key.h>
  40 #include <linux/binfmts.h>
  41 #include <linux/mman.h>
  42 #include <linux/mmu_notifier.h>
  43 #include <linux/fs.h>
  44 #include <linux/mm.h>
  45 #include <linux/vmacache.h>
  46 #include <linux/nsproxy.h>
  47 #include <linux/capability.h>
  48 #include <linux/cpu.h>
  49 #include <linux/cgroup.h>
  50 #include <linux/security.h>
  51 #include <linux/hugetlb.h>
  52 #include <linux/seccomp.h>
  53 #include <linux/swap.h>
  54 #include <linux/syscalls.h>
  55 #include <linux/jiffies.h>
  56 #include <linux/futex.h>
  57 #include <linux/compat.h>
  58 #include <linux/kthread.h>
  59 #include <linux/task_io_accounting_ops.h>
  60 #include <linux/rcupdate.h>
  61 #include <linux/ptrace.h>
  62 #include <linux/mount.h>
  63 #include <linux/audit.h>
  64 #include <linux/memcontrol.h>
  65 #include <linux/ftrace.h>
  66 #include <linux/proc_fs.h>
  67 #include <linux/profile.h>
  68 #include <linux/rmap.h>
  69 #include <linux/ksm.h>
  70 #include <linux/acct.h>
  71 #include <linux/userfaultfd_k.h>
  72 #include <linux/tsacct_kern.h>
  73 #include <linux/cn_proc.h>
  74 #include <linux/freezer.h>
  75 #include <linux/delayacct.h>
  76 #include <linux/taskstats_kern.h>
  77 #include <linux/random.h>
  78 #include <linux/tty.h>
  79 #include <linux/blkdev.h>
  80 #include <linux/fs_struct.h>
  81 #include <linux/magic.h>
  82 #include <linux/perf_event.h>
  83 #include <linux/posix-timers.h>
  84 #include <linux/user-return-notifier.h>
  85 #include <linux/oom.h>
  86 #include <linux/khugepaged.h>
  87 #include <linux/signalfd.h>
  88 #include <linux/uprobes.h>
  89 #include <linux/aio.h>
  90 #include <linux/compiler.h>
  91 #include <linux/sysctl.h>
  92 #include <linux/kcov.h>
  93 #include <linux/livepatch.h>
  94 #include <linux/thread_info.h>
  95 #include <linux/stackleak.h>
  96 #include <linux/kasan.h>
  97 #include <linux/scs.h>
  98 #include <linux/io_uring.h>
  99 #include <linux/bpf.h>
 100
 101 #include <asm/pgalloc.h>
 102 #include <linux/uaccess.h>
 103 #include <asm/mmu_context.h>
 104 #include <asm/cacheflush.h>
 105 #include <asm/tlbflush.h>
 106
 107 #include <trace/events/sched.h>
 108
 109 #define CREATE_TRACE_POINTS
 110 #include <trace/events/task.h>
 111
 112 /*
 113  * Minimum number of threads to boot the kernel
 114  */
 115 #define MIN_THREADS 20
 116
 117 /*
 118  * Maximum number of threads
 119  */
 120 #define MAX_THREADS FUTEX_TID_MASK
 121
 122 /*
 123  * Protected counters by write_lock_irq(&tasklist_lock)
 124  */
 125 unsigned long total_forks;      /* Handle normal Linux uptimes. */
 126 int nr_threads;                 /* The idle threads do not count.. */
 127
 128 static int max_threads;         /* tunable limit on nr_threads */
 129
 130 #define NAMED_ARRAY_INDEX(x)    [x] = __stringify(x)
 131
 132 static const char * const resident_page_types[] = {
 133         NAMED_ARRAY_INDEX(MM_FILEPAGES),
 134         NAMED_ARRAY_INDEX(MM_ANONPAGES),
 135         NAMED_ARRAY_INDEX(MM_SWAPENTS),
 136         NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
 137 };
 138
 139 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
 140
 141 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
 142
 143 #ifdef CONFIG_PROVE_RCU
 144 int lockdep_tasklist_lock_is_held(void)
 145 {
 146         return lockdep_is_held(&tasklist_lock);
 147 }
 148 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
 149 #endif /* #ifdef CONFIG_PROVE_RCU */
 150
 151 int nr_processes(void)
 152 {
 153         int cpu;
 154         int total = 0;
 155
 156         for_each_possible_cpu(cpu)
 157                 total += per_cpu(process_counts, cpu);
 158
 159         return total;
 160 }
 161
 162 void __weak arch_release_task_struct(struct task_struct *tsk)
 163 {
 164 }
 165
 166 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 167 static struct kmem_cache *task_struct_cachep;
 168
 169 static inline struct task_struct *alloc_task_struct_node(int node)
 170 {
 171         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
 172 }
 173
 174 static inline void free_task_struct(struct task_struct *tsk)
 175 {
 176         kmem_cache_free(task_struct_cachep, tsk);
 177 }
 178 #endif
 179
 180 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
 181
 182 /*
 183  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
 184  * kmemcache based allocator.
 185  */
 186 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
 187
 188 #ifdef CONFIG_VMAP_STACK
 189 /*
 190  * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
 191  * flush.  Try to minimize the number of calls by caching stacks.
 192  */
 193 #define NR_CACHED_STACKS 2
 194 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
 195
 196 static int free_vm_stack_cache(unsigned int cpu)
 197 {
 198         struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
 199         int i;
 200
 201         for (i = 0; i < NR_CACHED_STACKS; i++) {
 202                 struct vm_struct *vm_stack = cached_vm_stacks[i];
 203
 204                 if (!vm_stack)
 205                         continue;
 206
 207                 vfree(vm_stack->addr);
 208                 cached_vm_stacks[i] = NULL;
 209         }
 210
 211         return 0;
 212 }
 213 #endif
 214
 215 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
 216 {
 217 #ifdef CONFIG_VMAP_STACK
 218         void *stack;
 219         int i;
 220
 221         for (i = 0; i < NR_CACHED_STACKS; i++) {
 222                 struct vm_struct *s;
 223
 224                 s = this_cpu_xchg(cached_stacks[i], NULL);
 225
 226                 if (!s)
 227                         continue;
 228
 229                 /* Mark stack accessible for KASAN. */
 230                 kasan_unpoison_range(s->addr, THREAD_SIZE);
 231
 232                 /* Clear stale pointers from reused stack. */
 233                 memset(s->addr, 0, THREAD_SIZE);
 234
 235                 tsk->stack_vm_area = s;
 236                 tsk->stack = s->addr;
 237                 return s->addr;
 238         }
 239
 240         /*
 241          * Allocated stacks are cached and later reused by new threads,
 242          * so memcg accounting is performed manually on assigning/releasing
 243          * stacks to tasks. Drop __GFP_ACCOUNT.
 244          */
 245         stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
 246                                      VMALLOC_START, VMALLOC_END,
 247                                      THREADINFO_GFP & ~__GFP_ACCOUNT,
 248                                      PAGE_KERNEL,
 249                                      0, node, __builtin_return_address(0));
 250
 251         /*
 252          * We can't call find_vm_area() in interrupt context, and
 253          * free_thread_stack() can be called in interrupt context,
 254          * so cache the vm_struct.
 255          */
 256         if (stack) {
 257                 tsk->stack_vm_area = find_vm_area(stack);
 258                 tsk->stack = stack;
 259         }
 260         return stack;
 261 #else
 262         struct page *page = alloc_pages_node(node, THREADINFO_GFP,
 263                                              THREAD_SIZE_ORDER);
 264
 265         if (likely(page)) {
 266                 tsk->stack = kasan_reset_tag(page_address(page));
 267                 return tsk->stack;
 268         }
 269         return NULL;
 270 #endif
 271 }
 272
 273 static inline void free_thread_stack(struct task_struct *tsk)
 274 {
 275 #ifdef CONFIG_VMAP_STACK
 276         struct vm_struct *vm = task_stack_vm_area(tsk);
 277
 278         if (vm) {
 279                 int i;
 280
 281                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
 282                         memcg_kmem_uncharge_page(vm->pages[i], 0);
 283
 284                 for (i = 0; i < NR_CACHED_STACKS; i++) {
 285                         if (this_cpu_cmpxchg(cached_stacks[i],
 286                                         NULL, tsk->stack_vm_area) != NULL)
 287                                 continue;
 288
 289                         return;
 290                 }
 291
 292                 vfree_atomic(tsk->stack);
 293                 return;
 294         }
 295 #endif
 296
 297         __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
 298 }
 299 # else
 300 static struct kmem_cache *thread_stack_cache;
 301
 302 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
 303                                                   int node)
 304 {
 305         unsigned long *stack;
 306         stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
 307         stack = kasan_reset_tag(stack);
 308         tsk->stack = stack;
 309         return stack;
 310 }
 311
 312 static void free_thread_stack(struct task_struct *tsk)
 313 {
 314         kmem_cache_free(thread_stack_cache, tsk->stack);
 315 }
 316
 317 void thread_stack_cache_init(void)
 318 {
 319         thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
 320                                         THREAD_SIZE, THREAD_SIZE, 0, 0,
 321                                         THREAD_SIZE, NULL);
 322         BUG_ON(thread_stack_cache == NULL);
 323 }
 324 # endif
 325 #endif
 326
 327 /* SLAB cache for signal_struct structures (tsk->signal) */
 328 static struct kmem_cache *signal_cachep;
 329
 330 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 331 struct kmem_cache *sighand_cachep;
 332
 333 /* SLAB cache for files_struct structures (tsk->files) */
 334 struct kmem_cache *files_cachep;
 335
 336 /* SLAB cache for fs_struct structures (tsk->fs) */
 337 struct kmem_cache *fs_cachep;
 338
 339 /* SLAB cache for vm_area_struct structures */
 340 static struct kmem_cache *vm_area_cachep;
 341
 342 /* SLAB cache for mm_struct structures (tsk->mm) */
 343 static struct kmem_cache *mm_cachep;
 344
 345 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
 346 {
 347         struct vm_area_struct *vma;
 348
 349         vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 350         if (vma)
 351                 vma_init(vma, mm);
 352         return vma;
 353 }
 354
 355 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
 356 {
 357         struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 358
 359         if (new) {
 360                 ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
 361                 ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
 362                 /*
 363                  * orig->shared.rb may be modified concurrently, but the clone
 364                  * will be reinitialized.
 365                  */
 366                 *new = data_race(*orig);
 367                 INIT_LIST_HEAD(&new->anon_vma_chain);
 368                 new->vm_next = new->vm_prev = NULL;
 369         }
 370         return new;
 371 }
 372
 373 void vm_area_free(struct vm_area_struct *vma)
 374 {
 375         kmem_cache_free(vm_area_cachep, vma);
 376 }
 377
 378 static void account_kernel_stack(struct task_struct *tsk, int account)
 379 {
 380         void *stack = task_stack_page(tsk);
 381         struct vm_struct *vm = task_stack_vm_area(tsk);
 382
 383         if (vm) {
 384                 int i;
 385
 386                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
 387                         mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,
 388                                               account * (PAGE_SIZE / 1024));
 389         } else {
 390                 /* All stack pages are in the same node. */
 391                 mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB,
 392                                       account * (THREAD_SIZE / 1024));
 393         }
 394 }
 395
 396 static int memcg_charge_kernel_stack(struct task_struct *tsk)
 397 {
 398 #ifdef CONFIG_VMAP_STACK
 399         struct vm_struct *vm = task_stack_vm_area(tsk);
 400         int ret;
 401
 402         BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
 403
 404         if (vm) {
 405                 int i;
 406
 407                 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
 408
 409                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
 410                         /*
 411                          * If memcg_kmem_charge_page() fails, page's
 412                          * memory cgroup pointer is NULL, and
 413                          * memcg_kmem_uncharge_page() in free_thread_stack()
 414                          * will ignore this page.
 415                          */
 416                         ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL,
 417                                                      0);
 418                         if (ret)
 419                                 return ret;
 420                 }
 421         }
 422 #endif
 423         return 0;
 424 }
 425
 426 static void release_task_stack(struct task_struct *tsk)
 427 {
 428         if (WARN_ON(READ_ONCE(tsk->__state) != TASK_DEAD))
 429                 return;  /* Better to leak the stack than to free prematurely */
 430
 431         account_kernel_stack(tsk, -1);
 432         free_thread_stack(tsk);
 433         tsk->stack = NULL;
 434 #ifdef CONFIG_VMAP_STACK
 435         tsk->stack_vm_area = NULL;
 436 #endif
 437 }
 438
 439 #ifdef CONFIG_THREAD_INFO_IN_TASK
 440 void put_task_stack(struct task_struct *tsk)
 441 {
 442         if (refcount_dec_and_test(&tsk->stack_refcount))
 443                 release_task_stack(tsk);
 444 }
 445 #endif
 446
 447 void free_task(struct task_struct *tsk)
 448 {
 449         release_user_cpus_ptr(tsk);
 450         scs_release(tsk);
 451
 452 #ifndef CONFIG_THREAD_INFO_IN_TASK
 453         /*
 454          * The task is finally done with both the stack and thread_info,
 455          * so free both.
 456          */
 457         release_task_stack(tsk);
 458 #else
 459         /*
 460          * If the task had a separate stack allocation, it should be gone
 461          * by now.
 462          */
 463         WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
 464 #endif
 465         rt_mutex_debug_task_free(tsk);
 466         ftrace_graph_exit_task(tsk);
 467         arch_release_task_struct(tsk);
 468         if (tsk->flags & PF_KTHREAD)
 469                 free_kthread_struct(tsk);
 470         free_task_struct(tsk);
 471 }
 472 EXPORT_SYMBOL(free_task);
 473
 474 static void dup_mm_exe_file(struct mm_struct *mm, struct mm_struct *oldmm)
 475 {
 476         struct file *exe_file;
 477
 478         exe_file = get_mm_exe_file(oldmm);
 479         RCU_INIT_POINTER(mm->exe_file, exe_file);
 480         /*
 481          * We depend on the oldmm having properly denied write access to the
 482          * exe_file already.
 483          */
 484         if (exe_file && deny_write_access(exe_file))
 485                 pr_warn_once("deny_write_access() failed in %s\n", __func__);
 486 }
 487
 488 #ifdef CONFIG_MMU
 489 static __latent_entropy int dup_mmap(struct mm_struct *mm,
 490                                         struct mm_struct *oldmm)
 491 {
 492         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 493         struct rb_node **rb_link, *rb_parent;
 494         int retval;
 495         unsigned long charge;
 496         LIST_HEAD(uf);
 497
 498         uprobe_start_dup_mmap();
 499         if (mmap_write_lock_killable(oldmm)) {
 500                 retval = -EINTR;
 501                 goto fail_uprobe_end;
 502         }
 503         flush_cache_dup_mm(oldmm);
 504         uprobe_dup_mmap(oldmm, mm);
 505         /*
 506          * Not linked in yet - no deadlock potential:
 507          */
 508         mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING);
 509
 510         /* No ordering required: file already has been exposed. */
 511         dup_mm_exe_file(mm, oldmm);
 512
 513         mm->total_vm = oldmm->total_vm;
 514         mm->data_vm = oldmm->data_vm;
 515         mm->exec_vm = oldmm->exec_vm;
 516         mm->stack_vm = oldmm->stack_vm;
 517
 518         rb_link = &mm->mm_rb.rb_node;
 519         rb_parent = NULL;
 520         pprev = &mm->mmap;
 521         retval = ksm_fork(mm, oldmm);
 522         if (retval)
 523                 goto out;
 524         retval = khugepaged_fork(mm, oldmm);
 525         if (retval)
 526                 goto out;
 527
 528         prev = NULL;
 529         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 530                 struct file *file;
 531
 532                 if (mpnt->vm_flags & VM_DONTCOPY) {
 533                         vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
 534                         continue;
 535                 }
 536                 charge = 0;
 537                 /*
 538                  * Don't duplicate many vmas if we've been oom-killed (for
 539                  * example)
 540                  */
 541                 if (fatal_signal_pending(current)) {
 542                         retval = -EINTR;
 543                         goto out;
 544                 }
 545                 if (mpnt->vm_flags & VM_ACCOUNT) {
 546                         unsigned long len = vma_pages(mpnt);
 547
 548                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
 549                                 goto fail_nomem;
 550                         charge = len;
 551                 }
 552                 tmp = vm_area_dup(mpnt);
 553                 if (!tmp)
 554                         goto fail_nomem;
 555                 retval = vma_dup_policy(mpnt, tmp);
 556                 if (retval)
 557                         goto fail_nomem_policy;
 558                 tmp->vm_mm = mm;
 559                 retval = dup_userfaultfd(tmp, &uf);
 560                 if (retval)
 561                         goto fail_nomem_anon_vma_fork;
 562                 if (tmp->vm_flags & VM_WIPEONFORK) {
 563                         /*
 564                          * VM_WIPEONFORK gets a clean slate in the child.
 565                          * Don't prepare anon_vma until fault since we don't
 566                          * copy page for current vma.
 567                          */
 568                         tmp->anon_vma = NULL;
 569                 } else if (anon_vma_fork(tmp, mpnt))
 570                         goto fail_nomem_anon_vma_fork;
 571                 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
 572                 file = tmp->vm_file;
 573                 if (file) {
 574                         struct address_space *mapping = file->f_mapping;
 575
 576                         get_file(file);
 577                         i_mmap_lock_write(mapping);
 578                         if (tmp->vm_flags & VM_SHARED)
 579                                 mapping_allow_writable(mapping);
 580                         flush_dcache_mmap_lock(mapping);
 581                         /* insert tmp into the share list, just after mpnt */
 582                         vma_interval_tree_insert_after(tmp, mpnt,
 583                                         &mapping->i_mmap);
 584                         flush_dcache_mmap_unlock(mapping);
 585                         i_mmap_unlock_write(mapping);
 586                 }
 587
 588                 /*
 589                  * Clear hugetlb-related page reserves for children. This only
 590                  * affects MAP_PRIVATE mappings. Faults generated by the child
 591                  * are not guaranteed to succeed, even if read-only
 592                  */
 593                 if (is_vm_hugetlb_page(tmp))
 594                         reset_vma_resv_huge_pages(tmp);
 595
 596                 /*
 597                  * Link in the new vma and copy the page table entries.
 598                  */
 599                 *pprev = tmp;
 600                 pprev = &tmp->vm_next;
 601                 tmp->vm_prev = prev;
 602                 prev = tmp;
 603
 604                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 605                 rb_link = &tmp->vm_rb.rb_right;
 606                 rb_parent = &tmp->vm_rb;
 607
 608                 mm->map_count++;
 609                 if (!(tmp->vm_flags & VM_WIPEONFORK))
 610                         retval = copy_page_range(tmp, mpnt);
 611
 612                 if (tmp->vm_ops && tmp->vm_ops->open)
 613                         tmp->vm_ops->open(tmp);
 614
 615                 if (retval)
 616                         goto out;
 617         }
 618         /* a new mm has just been created */
 619         retval = arch_dup_mmap(oldmm, mm);
 620 out:
 621         mmap_write_unlock(mm);
 622         flush_tlb_mm(oldmm);
 623         mmap_write_unlock(oldmm);
 624         dup_userfaultfd_complete(&uf);
 625 fail_uprobe_end:
 626         uprobe_end_dup_mmap();
 627         return retval;
 628 fail_nomem_anon_vma_fork:
 629         mpol_put(vma_policy(tmp));
 630 fail_nomem_policy:
 631         vm_area_free(tmp);
 632 fail_nomem:
 633         retval = -ENOMEM;
 634         vm_unacct_memory(charge);
 635         goto out;
 636 }
 637
 638 static inline int mm_alloc_pgd(struct mm_struct *mm)
 639 {
 640         mm->pgd = pgd_alloc(mm);
 641         if (unlikely(!mm->pgd))
 642                 return -ENOMEM;
 643         return 0;
 644 }
 645
 646 static inline void mm_free_pgd(struct mm_struct *mm)
 647 {
 648         pgd_free(mm, mm->pgd);
 649 }
 650 #else
 651 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 652 {
 653         mmap_write_lock(oldmm);
 654         dup_mm_exe_file(mm, oldmm);
 655         mmap_write_unlock(oldmm);
 656         return 0;
 657 }
 658 #define mm_alloc_pgd(mm)        (0)
 659 #define mm_free_pgd(mm)
 660 #endif /* CONFIG_MMU */
 661
 662 static void check_mm(struct mm_struct *mm)
 663 {
 664         int i;
 665
 666         BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
 667                          "Please make sure 'struct resident_page_types[]' is updated as well");
 668
 669         for (i = 0; i < NR_MM_COUNTERS; i++) {
 670                 long x = atomic_long_read(&mm->rss_stat.count[i]);
 671
 672                 if (unlikely(x))
 673                         pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
 674                                  mm, resident_page_types[i], x);
 675         }
 676
 677         if (mm_pgtables_bytes(mm))
 678                 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
 679                                 mm_pgtables_bytes(mm));
 680
 681 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 682         VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
 683 #endif
 684 }
 685
 686 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 687 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 688
 689 /*
 690  * Called when the last reference to the mm
 691  * is dropped: either by a lazy thread or by
 692  * mmput. Free the page directory and the mm.
 693  */
 694 void __mmdrop(struct mm_struct *mm)
 695 {
 696         BUG_ON(mm == &init_mm);
 697         WARN_ON_ONCE(mm == current->mm);
 698         WARN_ON_ONCE(mm == current->active_mm);
 699         mm_free_pgd(mm);
 700         destroy_context(mm);
 701         mmu_notifier_subscriptions_destroy(mm);
 702         check_mm(mm);
 703         put_user_ns(mm->user_ns);
 704         free_mm(mm);
 705 }
 706 EXPORT_SYMBOL_GPL(__mmdrop);
 707
 708 static void mmdrop_async_fn(struct work_struct *work)
 709 {
 710         struct mm_struct *mm;
 711
 712         mm = container_of(work, struct mm_struct, async_put_work);
 713         __mmdrop(mm);
 714 }
 715
 716 static void mmdrop_async(struct mm_struct *mm)
 717 {
 718         if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
 719                 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
 720                 schedule_work(&mm->async_put_work);
 721         }
 722 }
 723
 724 static inline void free_signal_struct(struct signal_struct *sig)
 725 {
 726         taskstats_tgid_free(sig);
 727         sched_autogroup_exit(sig);
 728         /*
 729          * __mmdrop is not safe to call from softirq context on x86 due to
 730          * pgd_dtor so postpone it to the async context
 731          */
 732         if (sig->oom_mm)
 733                 mmdrop_async(sig->oom_mm);
 734         kmem_cache_free(signal_cachep, sig);
 735 }
 736
 737 static inline void put_signal_struct(struct signal_struct *sig)
 738 {
 739         if (refcount_dec_and_test(&sig->sigcnt))
 740                 free_signal_struct(sig);
 741 }
 742
 743 void __put_task_struct(struct task_struct *tsk)
 744 {
 745         WARN_ON(!tsk->exit_state);
 746         WARN_ON(refcount_read(&tsk->usage));
 747         WARN_ON(tsk == current);
 748
 749         io_uring_free(tsk);
 750         cgroup_free(tsk);
 751         task_numa_free(tsk, true);
 752         security_task_free(tsk);
 753         bpf_task_storage_free(tsk);
 754         exit_creds(tsk);
 755         delayacct_tsk_free(tsk);
 756         put_signal_struct(tsk->signal);
 757         sched_core_free(tsk);
 758
 759         if (!profile_handoff_task(tsk))
 760                 free_task(tsk);
 761 }
 762 EXPORT_SYMBOL_GPL(__put_task_struct);
 763
 764 void __init __weak arch_task_cache_init(void) { }
 765
 766 /*
 767  * set_max_threads
 768  */
 769 static void set_max_threads(unsigned int max_threads_suggested)
 770 {
 771         u64 threads;
 772         unsigned long nr_pages = totalram_pages();
 773
 774         /*
 775          * The number of threads shall be limited such that the thread
 776          * structures may only consume a small part of the available memory.
 777          */
 778         if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
 779                 threads = MAX_THREADS;
 780         else
 781                 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
 782                                     (u64) THREAD_SIZE * 8UL);
 783
 784         if (threads > max_threads_suggested)
 785                 threads = max_threads_suggested;
 786
 787         max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
 788 }
 789
 790 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
 791 /* Initialized by the architecture: */
 792 int arch_task_struct_size __read_mostly;
 793 #endif
 794
 795 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 796 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
 797 {
 798         /* Fetch thread_struct whitelist for the architecture. */
 799         arch_thread_struct_whitelist(offset, size);
 800
 801         /*
 802          * Handle zero-sized whitelist or empty thread_struct, otherwise
 803          * adjust offset to position of thread_struct in task_struct.
 804          */
 805         if (unlikely(*size == 0))
 806                 *offset = 0;
 807         else
 808                 *offset += offsetof(struct task_struct, thread);
 809 }
 810 #endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
 811
 812 void __init fork_init(void)
 813 {
 814         int i;
 815 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 816 #ifndef ARCH_MIN_TASKALIGN
 817 #define ARCH_MIN_TASKALIGN      0
 818 #endif
 819         int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
 820         unsigned long useroffset, usersize;
 821
 822         /* create a slab on which task_structs can be allocated */
 823         task_struct_whitelist(&useroffset, &usersize);
 824         task_struct_cachep = kmem_cache_create_usercopy("task_struct",
 825                         arch_task_struct_size, align,
 826                         SLAB_PANIC|SLAB_ACCOUNT,
 827                         useroffset, usersize, NULL);
 828 #endif
 829
 830         /* do the arch specific task caches init */
 831         arch_task_cache_init();
 832
 833         set_max_threads(MAX_THREADS);
 834
 835         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 836         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 837         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 838                 init_task.signal->rlim[RLIMIT_NPROC];
 839
 840         for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++)
 841                 init_user_ns.ucount_max[i] = max_threads/2;
 842
 843         set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC,      RLIM_INFINITY);
 844         set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE,   RLIM_INFINITY);
 845         set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
 846         set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK,    RLIM_INFINITY);
 847
 848 #ifdef CONFIG_VMAP_STACK
 849         cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
 850                           NULL, free_vm_stack_cache);
 851 #endif
 852
 853         scs_init();
 854
 855         lockdep_init_task(&init_task);
 856         uprobes_init();
 857 }
 858
 859 int __weak arch_dup_task_struct(struct task_struct *dst,
 860                                                struct task_struct *src)
 861 {
 862         *dst = *src;
 863         return 0;
 864 }
 865
 866 void set_task_stack_end_magic(struct task_struct *tsk)
 867 {
 868         unsigned long *stackend;
 869
 870         stackend = end_of_stack(tsk);
 871         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 872 }
 873
 874 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 875 {
 876         struct task_struct *tsk;
 877         unsigned long *stack;
 878         struct vm_struct *stack_vm_area __maybe_unused;
 879         int err;
 880
 881         if (node == NUMA_NO_NODE)
 882                 node = tsk_fork_get_node(orig);
 883         tsk = alloc_task_struct_node(node);
 884         if (!tsk)
 885                 return NULL;
 886
 887         stack = alloc_thread_stack_node(tsk, node);
 888         if (!stack)
 889                 goto free_tsk;
 890
 891         if (memcg_charge_kernel_stack(tsk))
 892                 goto free_stack;
 893
 894         stack_vm_area = task_stack_vm_area(tsk);
 895
 896         err = arch_dup_task_struct(tsk, orig);
 897
 898         /*
 899          * arch_dup_task_struct() clobbers the stack-related fields.  Make
 900          * sure they're properly initialized before using any stack-related
 901          * functions again.
 902          */
 903         tsk->stack = stack;
 904 #ifdef CONFIG_VMAP_STACK
 905         tsk->stack_vm_area = stack_vm_area;
 906 #endif
 907 #ifdef CONFIG_THREAD_INFO_IN_TASK
 908         refcount_set(&tsk->stack_refcount, 1);
 909 #endif
 910
 911         if (err)
 912                 goto free_stack;
 913
 914         err = scs_prepare(tsk, node);
 915         if (err)
 916                 goto free_stack;
 917
 918 #ifdef CONFIG_SECCOMP
 919         /*
 920          * We must handle setting up seccomp filters once we're under
 921          * the sighand lock in case orig has changed between now and
 922          * then. Until then, filter must be NULL to avoid messing up
 923          * the usage counts on the error path calling free_task.
 924          */
 925         tsk->seccomp.filter = NULL;
 926 #endif
 927
 928         setup_thread_stack(tsk, orig);
 929         clear_user_return_notifier(tsk);
 930         clear_tsk_need_resched(tsk);
 931         set_task_stack_end_magic(tsk);
 932         clear_syscall_work_syscall_user_dispatch(tsk);
 933
 934 #ifdef CONFIG_STACKPROTECTOR
 935         tsk->stack_canary = get_random_canary();
 936 #endif
 937         if (orig->cpus_ptr == &orig->cpus_mask)
 938                 tsk->cpus_ptr = &tsk->cpus_mask;
 939         dup_user_cpus_ptr(tsk, orig, node);
 940
 941         /*
 942          * One for the user space visible state that goes away when reaped.
 943          * One for the scheduler.
 944          */
 945         refcount_set(&tsk->rcu_users, 2);
 946         /* One for the rcu users */
 947         refcount_set(&tsk->usage, 1);
 948 #ifdef CONFIG_BLK_DEV_IO_TRACE
 949         tsk->btrace_seq = 0;
 950 #endif
 951         tsk->splice_pipe = NULL;
 952         tsk->task_frag.page = NULL;
 953         tsk->wake_q.next = NULL;
 954         tsk->pf_io_worker = NULL;
 955
 956         account_kernel_stack(tsk, 1);
 957
 958         kcov_task_init(tsk);
 959         kmap_local_fork(tsk);
 960
 961 #ifdef CONFIG_FAULT_INJECTION
 962         tsk->fail_nth = 0;
 963 #endif
 964
 965 #ifdef CONFIG_BLK_CGROUP
 966         tsk->throttle_queue = NULL;
 967         tsk->use_memdelay = 0;
 968 #endif
 969
 970 #ifdef CONFIG_MEMCG
 971         tsk->active_memcg = NULL;
 972 #endif
 973         return tsk;
 974
 975 free_stack:
 976         free_thread_stack(tsk);
 977 free_tsk:
 978         free_task_struct(tsk);
 979         return NULL;
 980 }
 981
 982 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 983
 984 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 985
 986 static int __init coredump_filter_setup(char *s)
 987 {
 988         default_dump_filter =
 989                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 990                 MMF_DUMP_FILTER_MASK;
 991         return 1;
 992 }
 993
 994 __setup("coredump_filter=", coredump_filter_setup);
 995
 996 #include <linux/init_task.h>
 997
 998 static void mm_init_aio(struct mm_struct *mm)
 999 {
1000 #ifdef CONFIG_AIO
1001         spin_lock_init(&mm->ioctx_lock);
1002         mm->ioctx_table = NULL;
1003 #endif
1004 }
1005
1006 static __always_inline void mm_clear_owner(struct mm_struct *mm,
1007                                            struct task_struct *p)
1008 {
1009 #ifdef CONFIG_MEMCG
1010         if (mm->owner == p)
1011                 WRITE_ONCE(mm->owner, NULL);
1012 #endif
1013 }
1014
1015 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1016 {
1017 #ifdef CONFIG_MEMCG
1018         mm->owner = p;
1019 #endif
1020 }
1021
1022 static void mm_init_pasid(struct mm_struct *mm)
1023 {
1024 #ifdef CONFIG_IOMMU_SUPPORT
1025         mm->pasid = INIT_PASID;
1026 #endif
1027 }
1028
1029 static void mm_init_uprobes_state(struct mm_struct *mm)
1030 {
1031 #ifdef CONFIG_UPROBES
1032         mm->uprobes_state.xol_area = NULL;
1033 #endif
1034 }
1035
1036 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1037         struct user_namespace *user_ns)
1038 {
1039         mm->mmap = NULL;
1040         mm->mm_rb = RB_ROOT;
1041         mm->vmacache_seqnum = 0;
1042         atomic_set(&mm->mm_users, 1);
1043         atomic_set(&mm->mm_count, 1);
1044         seqcount_init(&mm->write_protect_seq);
1045         mmap_init_lock(mm);
1046         INIT_LIST_HEAD(&mm->mmlist);
1047         mm->core_state = NULL;
1048         mm_pgtables_bytes_init(mm);
1049         mm->map_count = 0;
1050         mm->locked_vm = 0;
1051         atomic64_set(&mm->pinned_vm, 0);
1052         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1053         spin_lock_init(&mm->page_table_lock);
1054         spin_lock_init(&mm->arg_lock);
1055         mm_init_cpumask(mm);
1056         mm_init_aio(mm);
1057         mm_init_owner(mm, p);
1058         mm_init_pasid(mm);
1059         RCU_INIT_POINTER(mm->exe_file, NULL);
1060         mmu_notifier_subscriptions_init(mm);
1061         init_tlb_flush_pending(mm);
1062 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1063         mm->pmd_huge_pte = NULL;
1064 #endif
1065         mm_init_uprobes_state(mm);
1066
1067         if (current->mm) {
1068                 mm->flags = current->mm->flags & MMF_INIT_MASK;
1069                 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1070         } else {
1071                 mm->flags = default_dump_filter;
1072                 mm->def_flags = 0;
1073         }
1074
1075         if (mm_alloc_pgd(mm))
1076                 goto fail_nopgd;
1077
1078         if (init_new_context(p, mm))
1079                 goto fail_nocontext;
1080
1081         mm->user_ns = get_user_ns(user_ns);
1082         return mm;
1083
1084 fail_nocontext:
1085         mm_free_pgd(mm);
1086 fail_nopgd:
1087         free_mm(mm);
1088         return NULL;
1089 }
1090
1091 /*
1092  * Allocate and initialize an mm_struct.
1093  */
1094 struct mm_struct *mm_alloc(void)
1095 {
1096         struct mm_struct *mm;
1097
1098         mm = allocate_mm();
1099         if (!mm)
1100                 return NULL;
1101
1102         memset(mm, 0, sizeof(*mm));
1103         return mm_init(mm, current, current_user_ns());
1104 }
1105
1106 static inline void __mmput(struct mm_struct *mm)
1107 {
1108         VM_BUG_ON(atomic_read(&mm->mm_users));
1109
1110         uprobe_clear_state(mm);
1111         exit_aio(mm);
1112         ksm_exit(mm);
1113         khugepaged_exit(mm); /* must run before exit_mmap */
1114         exit_mmap(mm);
1115         mm_put_huge_zero_page(mm);
1116         set_mm_exe_file(mm, NULL);
1117         if (!list_empty(&mm->mmlist)) {
1118                 spin_lock(&mmlist_lock);
1119                 list_del(&mm->mmlist);
1120                 spin_unlock(&mmlist_lock);
1121         }
1122         if (mm->binfmt)
1123                 module_put(mm->binfmt->module);
1124         mmdrop(mm);
1125 }
1126
1127 /*
1128  * Decrement the use count and release all resources for an mm.
1129  */
1130 void mmput(struct mm_struct *mm)
1131 {
1132         might_sleep();
1133
1134         if (atomic_dec_and_test(&mm->mm_users))
1135                 __mmput(mm);
1136 }
1137 EXPORT_SYMBOL_GPL(mmput);
1138
1139 #ifdef CONFIG_MMU
1140 static void mmput_async_fn(struct work_struct *work)
1141 {
1142         struct mm_struct *mm = container_of(work, struct mm_struct,
1143                                             async_put_work);
1144
1145         __mmput(mm);
1146 }
1147
1148 void mmput_async(struct mm_struct *mm)
1149 {
1150         if (atomic_dec_and_test(&mm->mm_users)) {
1151                 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1152                 schedule_work(&mm->async_put_work);
1153         }
1154 }
1155 #endif
1156
1157 /**
1158  * set_mm_exe_file - change a reference to the mm's executable file
1159  *
1160  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1161  *
1162  * Main users are mmput() and sys_execve(). Callers prevent concurrent
1163  * invocations: in mmput() nobody alive left, in execve task is single
1164  * threaded.
1165  *
1166  * Can only fail if new_exe_file != NULL.
1167  */
1168 int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1169 {
1170         struct file *old_exe_file;
1171
1172         /*
1173          * It is safe to dereference the exe_file without RCU as
1174          * this function is only called if nobody else can access
1175          * this mm -- see comment above for justification.
1176          */
1177         old_exe_file = rcu_dereference_raw(mm->exe_file);
1178
1179         if (new_exe_file) {
1180                 /*
1181                  * We expect the caller (i.e., sys_execve) to already denied
1182                  * write access, so this is unlikely to fail.
1183                  */
1184                 if (unlikely(deny_write_access(new_exe_file)))
1185                         return -EACCES;
1186                 get_file(new_exe_file);
1187         }
1188         rcu_assign_pointer(mm->exe_file, new_exe_file);
1189         if (old_exe_file) {
1190                 allow_write_access(old_exe_file);
1191                 fput(old_exe_file);
1192         }
1193         return 0;
1194 }
1195
1196 /**
1197  * replace_mm_exe_file - replace a reference to the mm's executable file
1198  *
1199  * This changes mm's executable file (shown as symlink /proc/[pid]/exe),
1200  * dealing with concurrent invocation and without grabbing the mmap lock in
1201  * write mode.
1202  *
1203  * Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE).
1204  */
1205 int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1206 {
1207         struct vm_area_struct *vma;
1208         struct file *old_exe_file;
1209         int ret = 0;
1210
1211         /* Forbid mm->exe_file change if old file still mapped. */
1212         old_exe_file = get_mm_exe_file(mm);
1213         if (old_exe_file) {
1214                 mmap_read_lock(mm);
1215                 for (vma = mm->mmap; vma && !ret; vma = vma->vm_next) {
1216                         if (!vma->vm_file)
1217                                 continue;
1218                         if (path_equal(&vma->vm_file->f_path,
1219                                        &old_exe_file->f_path))
1220                                 ret = -EBUSY;
1221                 }
1222                 mmap_read_unlock(mm);
1223                 fput(old_exe_file);
1224                 if (ret)
1225                         return ret;
1226         }
1227
1228         /* set the new file, lockless */
1229         ret = deny_write_access(new_exe_file);
1230         if (ret)
1231                 return -EACCES;
1232         get_file(new_exe_file);
1233
1234         old_exe_file = xchg(&mm->exe_file, new_exe_file);
1235         if (old_exe_file) {
1236                 /*
1237                  * Don't race with dup_mmap() getting the file and disallowing
1238                  * write access while someone might open the file writable.
1239                  */
1240                 mmap_read_lock(mm);
1241                 allow_write_access(old_exe_file);
1242                 fput(old_exe_file);
1243                 mmap_read_unlock(mm);
1244         }
1245         return 0;
1246 }
1247
1248 /**
1249  * get_mm_exe_file - acquire a reference to the mm's executable file
1250  *
1251  * Returns %NULL if mm has no associated executable file.
1252  * User must release file via fput().
1253  */
1254 struct file *get_mm_exe_file(struct mm_struct *mm)
1255 {
1256         struct file *exe_file;
1257
1258         rcu_read_lock();
1259         exe_file = rcu_dereference(mm->exe_file);
1260         if (exe_file && !get_file_rcu(exe_file))
1261                 exe_file = NULL;
1262         rcu_read_unlock();
1263         return exe_file;
1264 }
1265 EXPORT_SYMBOL(get_mm_exe_file);
1266
1267 /**
1268  * get_task_exe_file - acquire a reference to the task's executable file
1269  *
1270  * Returns %NULL if task's mm (if any) has no associated executable file or
1271  * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1272  * User must release file via fput().
1273  */
1274 struct file *get_task_exe_file(struct task_struct *task)
1275 {
1276         struct file *exe_file = NULL;
1277         struct mm_struct *mm;
1278
1279         task_lock(task);
1280         mm = task->mm;
1281         if (mm) {
1282                 if (!(task->flags & PF_KTHREAD))
1283                         exe_file = get_mm_exe_file(mm);
1284         }
1285         task_unlock(task);
1286         return exe_file;
1287 }
1288 EXPORT_SYMBOL(get_task_exe_file);
1289
1290 /**
1291  * get_task_mm - acquire a reference to the task's mm
1292  *
1293  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
1294  * this kernel workthread has transiently adopted a user mm with use_mm,
1295  * to do its AIO) is not set and if so returns a reference to it, after
1296  * bumping up the use count.  User must release the mm via mmput()
1297  * after use.  Typically used by /proc and ptrace.
1298  */
1299 struct mm_struct *get_task_mm(struct task_struct *task)
1300 {
1301         struct mm_struct *mm;
1302
1303         task_lock(task);
1304         mm = task->mm;
1305         if (mm) {
1306                 if (task->flags & PF_KTHREAD)
1307                         mm = NULL;
1308                 else
1309                         mmget(mm);
1310         }
1311         task_unlock(task);
1312         return mm;
1313 }
1314 EXPORT_SYMBOL_GPL(get_task_mm);
1315
1316 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1317 {
1318         struct mm_struct *mm;
1319         int err;
1320
1321         err =  down_read_killable(&task->signal->exec_update_lock);
1322         if (err)
1323                 return ERR_PTR(err);
1324
1325         mm = get_task_mm(task);
1326         if (mm && mm != current->mm &&
1327                         !ptrace_may_access(task, mode)) {
1328                 mmput(mm);
1329                 mm = ERR_PTR(-EACCES);
1330         }
1331         up_read(&task->signal->exec_update_lock);
1332
1333         return mm;
1334 }
1335
1336 static void complete_vfork_done(struct task_struct *tsk)
1337 {
1338         struct completion *vfork;
1339
1340         task_lock(tsk);
1341         vfork = tsk->vfork_done;
1342         if (likely(vfork)) {
1343                 tsk->vfork_done = NULL;
1344                 complete(vfork);
1345         }
1346         task_unlock(tsk);
1347 }
1348
1349 static int wait_for_vfork_done(struct task_struct *child,
1350                                 struct completion *vfork)
1351 {
1352         int killed;
1353
1354         freezer_do_not_count();
1355         cgroup_enter_frozen();
1356         killed = wait_for_completion_killable(vfork);
1357         cgroup_leave_frozen(false);
1358         freezer_count();
1359
1360         if (killed) {
1361                 task_lock(child);
1362                 child->vfork_done = NULL;
1363                 task_unlock(child);
1364         }
1365
1366         put_task_struct(child);
1367         return killed;
1368 }
1369
1370 /* Please note the differences between mmput and mm_release.
1371  * mmput is called whenever we stop holding onto a mm_struct,
1372  * error success whatever.
1373  *
1374  * mm_release is called after a mm_struct has been removed
1375  * from the current process.
1376  *
1377  * This difference is important for error handling, when we
1378  * only half set up a mm_struct for a new process and need to restore
1379  * the old one.  Because we mmput the new mm_struct before
1380  * restoring the old one. . .
1381  * Eric Biederman 10 January 1998
1382  */
1383 static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1384 {
1385         uprobe_free_utask(tsk);
1386
1387         /* Get rid of any cached register state */
1388         deactivate_mm(tsk, mm);
1389
1390         /*
1391          * Signal userspace if we're not exiting with a core dump
1392          * because we want to leave the value intact for debugging
1393          * purposes.
1394          */
1395         if (tsk->clear_child_tid) {
1396                 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1397                     atomic_read(&mm->mm_users) > 1) {
1398                         /*
1399                          * We don't check the error code - if userspace has
1400                          * not set up a proper pointer then tough luck.
1401                          */
1402                         put_user(0, tsk->clear_child_tid);
1403                         do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1404                                         1, NULL, NULL, 0, 0);
1405                 }
1406                 tsk->clear_child_tid = NULL;
1407         }
1408
1409         /*
1410          * All done, finally we can wake up parent and return this mm to him.
1411          * Also kthread_stop() uses this completion for synchronization.
1412          */
1413         if (tsk->vfork_done)
1414                 complete_vfork_done(tsk);
1415 }
1416
1417 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1418 {
1419         futex_exit_release(tsk);
1420         mm_release(tsk, mm);
1421 }
1422
1423 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1424 {
1425         futex_exec_release(tsk);
1426         mm_release(tsk, mm);
1427 }
1428
1429 /**
1430  * dup_mm() - duplicates an existing mm structure
1431  * @tsk: the task_struct with which the new mm will be associated.
1432  * @oldmm: the mm to duplicate.
1433  *
1434  * Allocates a new mm structure and duplicates the provided @oldmm structure
1435  * content into it.
1436  *
1437  * Return: the duplicated mm or NULL on failure.
1438  */
1439 static struct mm_struct *dup_mm(struct task_struct *tsk,
1440                                 struct mm_struct *oldmm)
1441 {
1442         struct mm_struct *mm;
1443         int err;
1444
1445         mm = allocate_mm();
1446         if (!mm)
1447                 goto fail_nomem;
1448
1449         memcpy(mm, oldmm, sizeof(*mm));
1450
1451         if (!mm_init(mm, tsk, mm->user_ns))
1452                 goto fail_nomem;
1453
1454         err = dup_mmap(mm, oldmm);
1455         if (err)
1456                 goto free_pt;
1457
1458         mm->hiwater_rss = get_mm_rss(mm);
1459         mm->hiwater_vm = mm->total_vm;
1460
1461         if (mm->binfmt && !try_module_get(mm->binfmt->module))
1462                 goto free_pt;
1463
1464         return mm;
1465
1466 free_pt:
1467         /* don't put binfmt in mmput, we haven't got module yet */
1468         mm->binfmt = NULL;
1469         mm_init_owner(mm, NULL);
1470         mmput(mm);
1471
1472 fail_nomem:
1473         return NULL;
1474 }
1475
1476 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1477 {
1478         struct mm_struct *mm, *oldmm;
1479
1480         tsk->min_flt = tsk->maj_flt = 0;
1481         tsk->nvcsw = tsk->nivcsw = 0;
1482 #ifdef CONFIG_DETECT_HUNG_TASK
1483         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1484         tsk->last_switch_time = 0;
1485 #endif
1486
1487         tsk->mm = NULL;
1488         tsk->active_mm = NULL;
1489
1490         /*
1491          * Are we cloning a kernel thread?
1492          *
1493          * We need to steal a active VM for that..
1494          */
1495         oldmm = current->mm;
1496         if (!oldmm)
1497                 return 0;
1498
1499         /* initialize the new vmacache entries */
1500         vmacache_flush(tsk);
1501
1502         if (clone_flags & CLONE_VM) {
1503                 mmget(oldmm);
1504                 mm = oldmm;
1505         } else {
1506                 mm = dup_mm(tsk, current->mm);
1507                 if (!mm)
1508                         return -ENOMEM;
1509         }
1510
1511         tsk->mm = mm;
1512         tsk->active_mm = mm;
1513         return 0;
1514 }
1515
1516 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1517 {
1518         struct fs_struct *fs = current->fs;
1519         if (clone_flags & CLONE_FS) {
1520                 /* tsk->fs is already what we want */
1521                 spin_lock(&fs->lock);
1522                 if (fs->in_exec) {
1523                         spin_unlock(&fs->lock);
1524                         return -EAGAIN;
1525                 }
1526                 fs->users++;
1527                 spin_unlock(&fs->lock);
1528                 return 0;
1529         }
1530         tsk->fs = copy_fs_struct(fs);
1531         if (!tsk->fs)
1532                 return -ENOMEM;
1533         return 0;
1534 }
1535
1536 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1537 {
1538         struct files_struct *oldf, *newf;
1539         int error = 0;
1540
1541         /*
1542          * A background process may not have any files ...
1543          */
1544         oldf = current->files;
1545         if (!oldf)
1546                 goto out;
1547
1548         if (clone_flags & CLONE_FILES) {
1549                 atomic_inc(&oldf->count);
1550                 goto out;
1551         }
1552
1553         newf = dup_fd(oldf, NR_OPEN_MAX, &error);
1554         if (!newf)
1555                 goto out;
1556
1557         tsk->files = newf;
1558         error = 0;
1559 out:
1560         return error;
1561 }
1562
1563 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1564 {
1565 #ifdef CONFIG_BLOCK
1566         struct io_context *ioc = current->io_context;
1567         struct io_context *new_ioc;
1568
1569         if (!ioc)
1570                 return 0;
1571         /*
1572          * Share io context with parent, if CLONE_IO is set
1573          */
1574         if (clone_flags & CLONE_IO) {
1575                 ioc_task_link(ioc);
1576                 tsk->io_context = ioc;
1577         } else if (ioprio_valid(ioc->ioprio)) {
1578                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1579                 if (unlikely(!new_ioc))
1580                         return -ENOMEM;
1581
1582                 new_ioc->ioprio = ioc->ioprio;
1583                 put_io_context(new_ioc);
1584         }
1585 #endif
1586         return 0;
1587 }
1588
1589 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1590 {
1591         struct sighand_struct *sig;
1592
1593         if (clone_flags & CLONE_SIGHAND) {
1594                 refcount_inc(&current->sighand->count);
1595                 return 0;
1596         }
1597         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1598         RCU_INIT_POINTER(tsk->sighand, sig);
1599         if (!sig)
1600                 return -ENOMEM;
1601
1602         refcount_set(&sig->count, 1);
1603         spin_lock_irq(&current->sighand->siglock);
1604         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1605         spin_unlock_irq(&current->sighand->siglock);
1606
1607         /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
1608         if (clone_flags & CLONE_CLEAR_SIGHAND)
1609                 flush_signal_handlers(tsk, 0);
1610
1611         return 0;
1612 }
1613
1614 void __cleanup_sighand(struct sighand_struct *sighand)
1615 {
1616         if (refcount_dec_and_test(&sighand->count)) {
1617                 signalfd_cleanup(sighand);
1618                 /*
1619                  * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1620                  * without an RCU grace period, see __lock_task_sighand().
1621                  */
1622                 kmem_cache_free(sighand_cachep, sighand);
1623         }
1624 }
1625
1626 /*
1627  * Initialize POSIX timer handling for a thread group.
1628  */
1629 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1630 {
1631         struct posix_cputimers *pct = &sig->posix_cputimers;
1632         unsigned long cpu_limit;
1633
1634         cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1635         posix_cputimers_group_init(pct, cpu_limit);
1636 }
1637
1638 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1639 {
1640         struct signal_struct *sig;
1641
1642         if (clone_flags & CLONE_THREAD)
1643                 return 0;
1644
1645         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1646         tsk->signal = sig;
1647         if (!sig)
1648                 return -ENOMEM;
1649
1650         sig->nr_threads = 1;
1651         atomic_set(&sig->live, 1);
1652         refcount_set(&sig->sigcnt, 1);
1653
1654         /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1655         sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1656         tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1657
1658         init_waitqueue_head(&sig->wait_chldexit);
1659         sig->curr_target = tsk;
1660         init_sigpending(&sig->shared_pending);
1661         INIT_HLIST_HEAD(&sig->multiprocess);
1662         seqlock_init(&sig->stats_lock);
1663         prev_cputime_init(&sig->prev_cputime);
1664
1665 #ifdef CONFIG_POSIX_TIMERS
1666         INIT_LIST_HEAD(&sig->posix_timers);
1667         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1668         sig->real_timer.function = it_real_fn;
1669 #endif
1670
1671         task_lock(current->group_leader);
1672         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1673         task_unlock(current->group_leader);
1674
1675         posix_cpu_timers_init_group(sig);
1676
1677         tty_audit_fork(sig);
1678         sched_autogroup_fork(sig);
1679
1680         sig->oom_score_adj = current->signal->oom_score_adj;
1681         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1682
1683         mutex_init(&sig->cred_guard_mutex);
1684         init_rwsem(&sig->exec_update_lock);
1685
1686         return 0;
1687 }
1688
1689 static void copy_seccomp(struct task_struct *p)
1690 {
1691 #ifdef CONFIG_SECCOMP
1692         /*
1693          * Must be called with sighand->lock held, which is common to
1694          * all threads in the group. Holding cred_guard_mutex is not
1695          * needed because this new task is not yet running and cannot
1696          * be racing exec.
1697          */
1698         assert_spin_locked(&current->sighand->siglock);
1699
1700         /* Ref-count the new filter user, and assign it. */
1701         get_seccomp_filter(current);
1702         p->seccomp = current->seccomp;
1703
1704         /*
1705          * Explicitly enable no_new_privs here in case it got set
1706          * between the task_struct being duplicated and holding the
1707          * sighand lock. The seccomp state and nnp must be in sync.
1708          */
1709         if (task_no_new_privs(current))
1710                 task_set_no_new_privs(p);
1711
1712         /*
1713          * If the parent gained a seccomp mode after copying thread
1714          * flags and between before we held the sighand lock, we have
1715          * to manually enable the seccomp thread flag here.
1716          */
1717         if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1718                 set_task_syscall_work(p, SECCOMP);
1719 #endif
1720 }
1721
1722 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1723 {
1724         current->clear_child_tid = tidptr;
1725
1726         return task_pid_vnr(current);
1727 }
1728
1729 static void rt_mutex_init_task(struct task_struct *p)
1730 {
1731         raw_spin_lock_init(&p->pi_lock);
1732 #ifdef CONFIG_RT_MUTEXES
1733         p->pi_waiters = RB_ROOT_CACHED;
1734         p->pi_top_task = NULL;
1735         p->pi_blocked_on = NULL;
1736 #endif
1737 }
1738
1739 static inline void init_task_pid_links(struct task_struct *task)
1740 {
1741         enum pid_type type;
1742
1743         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type)
1744                 INIT_HLIST_NODE(&task->pid_links[type]);
1745 }
1746
1747 static inline void
1748 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1749 {
1750         if (type == PIDTYPE_PID)
1751                 task->thread_pid = pid;
1752         else
1753                 task->signal->pids[type] = pid;
1754 }
1755
1756 static inline void rcu_copy_process(struct task_struct *p)
1757 {
1758 #ifdef CONFIG_PREEMPT_RCU
1759         p->rcu_read_lock_nesting = 0;
1760         p->rcu_read_unlock_special.s = 0;
1761         p->rcu_blocked_node = NULL;
1762         INIT_LIST_HEAD(&p->rcu_node_entry);
1763 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1764 #ifdef CONFIG_TASKS_RCU
1765         p->rcu_tasks_holdout = false;
1766         INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1767         p->rcu_tasks_idle_cpu = -1;
1768 #endif /* #ifdef CONFIG_TASKS_RCU */
1769 #ifdef CONFIG_TASKS_TRACE_RCU
1770         p->trc_reader_nesting = 0;
1771         p->trc_reader_special.s = 0;
1772         INIT_LIST_HEAD(&p->trc_holdout_list);
1773 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
1774 }
1775
1776 struct pid *pidfd_pid(const struct file *file)
1777 {
1778         if (file->f_op == &pidfd_fops)
1779                 return file->private_data;
1780
1781         return ERR_PTR(-EBADF);
1782 }
1783
1784 static int pidfd_release(struct inode *inode, struct file *file)
1785 {
1786         struct pid *pid = file->private_data;
1787
1788         file->private_data = NULL;
1789         put_pid(pid);
1790         return 0;
1791 }
1792
1793 #ifdef CONFIG_PROC_FS
1794 /**
1795  * pidfd_show_fdinfo - print information about a pidfd
1796  * @m: proc fdinfo file
1797  * @f: file referencing a pidfd
1798  *
1799  * Pid:
1800  * This function will print the pid that a given pidfd refers to in the
1801  * pid namespace of the procfs instance.
1802  * If the pid namespace of the process is not a descendant of the pid
1803  * namespace of the procfs instance 0 will be shown as its pid. This is
1804  * similar to calling getppid() on a process whose parent is outside of
1805  * its pid namespace.
1806  *
1807  * NSpid:
1808  * If pid namespaces are supported then this function will also print
1809  * the pid of a given pidfd refers to for all descendant pid namespaces
1810  * starting from the current pid namespace of the instance, i.e. the
1811  * Pid field and the first entry in the NSpid field will be identical.
1812  * If the pid namespace of the process is not a descendant of the pid
1813  * namespace of the procfs instance 0 will be shown as its first NSpid
1814  * entry and no others will be shown.
1815  * Note that this differs from the Pid and NSpid fields in
1816  * /proc/<pid>/status where Pid and NSpid are always shown relative to
1817  * the  pid namespace of the procfs instance. The difference becomes
1818  * obvious when sending around a pidfd between pid namespaces from a
1819  * different branch of the tree, i.e. where no ancestral relation is
1820  * present between the pid namespaces:
1821  * - create two new pid namespaces ns1 and ns2 in the initial pid
1822  *   namespace (also take care to create new mount namespaces in the
1823  *   new pid namespace and mount procfs)
1824  * - create a process with a pidfd in ns1
1825  * - send pidfd from ns1 to ns2
1826  * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
1827  *   have exactly one entry, which is 0
1828  */
1829 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1830 {
1831         struct pid *pid = f->private_data;
1832         struct pid_namespace *ns;
1833         pid_t nr = -1;
1834
1835         if (likely(pid_has_task(pid, PIDTYPE_PID))) {
1836                 ns = proc_pid_ns(file_inode(m->file)->i_sb);
1837                 nr = pid_nr_ns(pid, ns);
1838         }
1839
1840         seq_put_decimal_ll(m, "Pid:\t", nr);
1841
1842 #ifdef CONFIG_PID_NS
1843         seq_put_decimal_ll(m, "\nNSpid:\t", nr);
1844         if (nr > 0) {
1845                 int i;
1846
1847                 /* If nr is non-zero it means that 'pid' is valid and that
1848                  * ns, i.e. the pid namespace associated with the procfs
1849                  * instance, is in the pid namespace hierarchy of pid.
1850                  * Start at one below the already printed level.
1851                  */
1852                 for (i = ns->level + 1; i <= pid->level; i++)
1853                         seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
1854         }
1855 #endif
1856         seq_putc(m, '\n');
1857 }
1858 #endif
1859
1860 /*
1861  * Poll support for process exit notification.
1862  */
1863 static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
1864 {
1865         struct pid *pid = file->private_data;
1866         __poll_t poll_flags = 0;
1867
1868         poll_wait(file, &pid->wait_pidfd, pts);
1869
1870         /*
1871          * Inform pollers only when the whole thread group exits.
1872          * If the thread group leader exits before all other threads in the
1873          * group, then poll(2) should block, similar to the wait(2) family.
1874          */
1875         if (thread_group_exited(pid))
1876                 poll_flags = EPOLLIN | EPOLLRDNORM;
1877
1878         return poll_flags;
1879 }
1880
1881 const struct file_operations pidfd_fops = {
1882         .release = pidfd_release,
1883         .poll = pidfd_poll,
1884 #ifdef CONFIG_PROC_FS
1885         .show_fdinfo = pidfd_show_fdinfo,
1886 #endif
1887 };
1888
1889 static void __delayed_free_task(struct rcu_head *rhp)
1890 {
1891         struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1892
1893         free_task(tsk);
1894 }
1895
1896 static __always_inline void delayed_free_task(struct task_struct *tsk)
1897 {
1898         if (IS_ENABLED(CONFIG_MEMCG))
1899                 call_rcu(&tsk->rcu, __delayed_free_task);
1900         else
1901                 free_task(tsk);
1902 }
1903
1904 static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk)
1905 {
1906         /* Skip if kernel thread */
1907         if (!tsk->mm)
1908                 return;
1909
1910         /* Skip if spawning a thread or using vfork */
1911         if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM)
1912                 return;
1913
1914         /* We need to synchronize with __set_oom_adj */
1915         mutex_lock(&oom_adj_mutex);
1916         set_bit(MMF_MULTIPROCESS, &tsk->mm->flags);
1917         /* Update the values in case they were changed after copy_signal */
1918         tsk->signal->oom_score_adj = current->signal->oom_score_adj;
1919         tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min;
1920         mutex_unlock(&oom_adj_mutex);
1921 }
1922
1923 /*
1924  * This creates a new process as a copy of the old one,
1925  * but does not actually start it yet.
1926  *
1927  * It copies the registers, and all the appropriate
1928  * parts of the process environment (as per the clone
1929  * flags). The actual kick-off is left to the caller.
1930  */
1931 static __latent_entropy struct task_struct *copy_process(
1932                                         struct pid *pid,
1933                                         int trace,
1934                                         int node,
1935                                         struct kernel_clone_args *args)
1936 {
1937         int pidfd = -1, retval;
1938         struct task_struct *p;
1939         struct multiprocess_signals delayed;
1940         struct file *pidfile = NULL;
1941         u64 clone_flags = args->flags;
1942         struct nsproxy *nsp = current->nsproxy;
1943
1944         /*
1945          * Don't allow sharing the root directory with processes in a different
1946          * namespace
1947          */
1948         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1949                 return ERR_PTR(-EINVAL);
1950
1951         if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1952                 return ERR_PTR(-EINVAL);
1953
1954         /*
1955          * Thread groups must share signals as well, and detached threads
1956          * can only be started up within the thread group.
1957          */
1958         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1959                 return ERR_PTR(-EINVAL);
1960
1961         /*
1962          * Shared signal handlers imply shared VM. By way of the above,
1963          * thread groups also imply shared VM. Blocking this case allows
1964          * for various simplifications in other code.
1965          */
1966         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1967                 return ERR_PTR(-EINVAL);
1968
1969         /*
1970          * Siblings of global init remain as zombies on exit since they are
1971          * not reaped by their parent (swapper). To solve this and to avoid
1972          * multi-rooted process trees, prevent global and container-inits
1973          * from creating siblings.
1974          */
1975         if ((clone_flags & CLONE_PARENT) &&
1976                                 current->signal->flags & SIGNAL_UNKILLABLE)
1977                 return ERR_PTR(-EINVAL);
1978
1979         /*
1980          * If the new process will be in a different pid or user namespace
1981          * do not allow it to share a thread group with the forking task.
1982          */
1983         if (clone_flags & CLONE_THREAD) {
1984                 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1985                     (task_active_pid_ns(current) != nsp->pid_ns_for_children))
1986                         return ERR_PTR(-EINVAL);
1987         }
1988
1989         /*
1990          * If the new process will be in a different time namespace
1991          * do not allow it to share VM or a thread group with the forking task.
1992          */
1993         if (clone_flags & (CLONE_THREAD | CLONE_VM)) {
1994                 if (nsp->time_ns != nsp->time_ns_for_children)
1995                         return ERR_PTR(-EINVAL);
1996         }
1997
1998         if (clone_flags & CLONE_PIDFD) {
1999                 /*
2000                  * - CLONE_DETACHED is blocked so that we can potentially
2001                  *   reuse it later for CLONE_PIDFD.
2002                  * - CLONE_THREAD is blocked until someone really needs it.
2003                  */
2004                 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
2005                         return ERR_PTR(-EINVAL);
2006         }
2007
2008         /*
2009          * Force any signals received before this point to be delivered
2010          * before the fork happens.  Collect up signals sent to multiple
2011          * processes that happen during the fork and delay them so that
2012          * they appear to happen after the fork.
2013          */
2014         sigemptyset(&delayed.signal);
2015         INIT_HLIST_NODE(&delayed.node);
2016
2017         spin_lock_irq(&current->sighand->siglock);
2018         if (!(clone_flags & CLONE_THREAD))
2019                 hlist_add_head(&delayed.node, &current->signal->multiprocess);
2020         recalc_sigpending();
2021         spin_unlock_irq(&current->sighand->siglock);
2022         retval = -ERESTARTNOINTR;
2023         if (task_sigpending(current))
2024                 goto fork_out;
2025
2026         retval = -ENOMEM;
2027         p = dup_task_struct(current, node);
2028         if (!p)
2029                 goto fork_out;
2030         if (args->io_thread) {
2031                 /*
2032                  * Mark us an IO worker, and block any signal that isn't
2033                  * fatal or STOP
2034                  */
2035                 p->flags |= PF_IO_WORKER;
2036                 siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
2037         }
2038
2039         /*
2040          * This _must_ happen before we call free_task(), i.e. before we jump
2041          * to any of the bad_fork_* labels. This is to avoid freeing
2042          * p->set_child_tid which is (ab)used as a kthread's data pointer for
2043          * kernel threads (PF_KTHREAD).
2044          */
2045         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
2046         /*
2047          * Clear TID on mm_release()?
2048          */
2049         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
2050
2051         ftrace_graph_init_task(p);
2052
2053         rt_mutex_init_task(p);
2054
2055         lockdep_assert_irqs_enabled();
2056 #ifdef CONFIG_PROVE_LOCKING
2057         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
2058 #endif
2059         retval = -EAGAIN;
2060         if (is_ucounts_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
2061                 if (p->real_cred->user != INIT_USER &&
2062                     !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
2063                         goto bad_fork_free;
2064         }
2065         current->flags &= ~PF_NPROC_EXCEEDED;
2066
2067         retval = copy_creds(p, clone_flags);
2068         if (retval < 0)
2069                 goto bad_fork_free;
2070
2071         /*
2072          * If multiple threads are within copy_process(), then this check
2073          * triggers too late. This doesn't hurt, the check is only there
2074          * to stop root fork bombs.
2075          */
2076         retval = -EAGAIN;
2077         if (data_race(nr_threads >= max_threads))
2078                 goto bad_fork_cleanup_count;
2079
2080         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
2081         p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE | PF_NO_SETAFFINITY);
2082         p->flags |= PF_FORKNOEXEC;
2083         INIT_LIST_HEAD(&p->children);
2084         INIT_LIST_HEAD(&p->sibling);
2085         rcu_copy_process(p);
2086         p->vfork_done = NULL;
2087         spin_lock_init(&p->alloc_lock);
2088
2089         init_sigpending(&p->pending);
2090
2091         p->utime = p->stime = p->gtime = 0;
2092 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
2093         p->utimescaled = p->stimescaled = 0;
2094 #endif
2095         prev_cputime_init(&p->prev_cputime);
2096
2097 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
2098         seqcount_init(&p->vtime.seqcount);
2099         p->vtime.starttime = 0;
2100         p->vtime.state = VTIME_INACTIVE;
2101 #endif
2102
2103 #ifdef CONFIG_IO_URING
2104         p->io_uring = NULL;
2105 #endif
2106
2107 #if defined(SPLIT_RSS_COUNTING)
2108         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
2109 #endif
2110
2111         p->default_timer_slack_ns = current->timer_slack_ns;
2112
2113 #ifdef CONFIG_PSI
2114         p->psi_flags = 0;
2115 #endif
2116
2117         task_io_accounting_init(&p->ioac);
2118         acct_clear_integrals(p);
2119
2120         posix_cputimers_init(&p->posix_cputimers);
2121
2122         p->io_context = NULL;
2123         audit_set_context(p, NULL);
2124         cgroup_fork(p);
2125 #ifdef CONFIG_NUMA
2126         p->mempolicy = mpol_dup(p->mempolicy);
2127         if (IS_ERR(p->mempolicy)) {
2128                 retval = PTR_ERR(p->mempolicy);
2129                 p->mempolicy = NULL;
2130                 goto bad_fork_cleanup_threadgroup_lock;
2131         }
2132 #endif
2133 #ifdef CONFIG_CPUSETS
2134         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
2135         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
2136         seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
2137 #endif
2138 #ifdef CONFIG_TRACE_IRQFLAGS
2139         memset(&p->irqtrace, 0, sizeof(p->irqtrace));
2140         p->irqtrace.hardirq_disable_ip  = _THIS_IP_;
2141         p->irqtrace.softirq_enable_ip   = _THIS_IP_;
2142         p->softirqs_enabled             = 1;
2143         p->softirq_context              = 0;
2144 #endif
2145
2146         p->pagefault_disabled = 0;
2147
2148 #ifdef CONFIG_LOCKDEP
2149         lockdep_init_task(p);
2150 #endif
2151
2152 #ifdef CONFIG_DEBUG_MUTEXES
2153         p->blocked_on = NULL; /* not blocked yet */
2154 #endif
2155 #ifdef CONFIG_BCACHE
2156         p->sequential_io        = 0;
2157         p->sequential_io_avg    = 0;
2158 #endif
2159 #ifdef CONFIG_BPF_SYSCALL
2160         RCU_INIT_POINTER(p->bpf_storage, NULL);
2161         p->bpf_ctx = NULL;
2162 #endif
2163
2164         /* Perform scheduler related setup. Assign this task to a CPU. */
2165         retval = sched_fork(clone_flags, p);
2166         if (retval)
2167                 goto bad_fork_cleanup_policy;
2168
2169         retval = perf_event_init_task(p, clone_flags);
2170         if (retval)
2171                 goto bad_fork_cleanup_policy;
2172         retval = audit_alloc(p);
2173         if (retval)
2174                 goto bad_fork_cleanup_perf;
2175         /* copy all the process information */
2176         shm_init_task(p);
2177         retval = security_task_alloc(p, clone_flags);
2178         if (retval)
2179                 goto bad_fork_cleanup_audit;
2180         retval = copy_semundo(clone_flags, p);
2181         if (retval)
2182                 goto bad_fork_cleanup_security;
2183         retval = copy_files(clone_flags, p);
2184         if (retval)
2185                 goto bad_fork_cleanup_semundo;
2186         retval = copy_fs(clone_flags, p);
2187         if (retval)
2188                 goto bad_fork_cleanup_files;
2189         retval = copy_sighand(clone_flags, p);
2190         if (retval)
2191                 goto bad_fork_cleanup_fs;
2192         retval = copy_signal(clone_flags, p);
2193         if (retval)
2194                 goto bad_fork_cleanup_sighand;
2195         retval = copy_mm(clone_flags, p);
2196         if (retval)
2197                 goto bad_fork_cleanup_signal;
2198         retval = copy_namespaces(clone_flags, p);
2199         if (retval)
2200                 goto bad_fork_cleanup_mm;
2201         retval = copy_io(clone_flags, p);
2202         if (retval)
2203                 goto bad_fork_cleanup_namespaces;
2204         retval = copy_thread(clone_flags, args->stack, args->stack_size, p, args->tls);
2205         if (retval)
2206                 goto bad_fork_cleanup_io;
2207
2208         stackleak_task_init(p);
2209
2210         if (pid != &init_struct_pid) {
2211                 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
2212                                 args->set_tid_size);
2213                 if (IS_ERR(pid)) {
2214                         retval = PTR_ERR(pid);
2215                         goto bad_fork_cleanup_thread;
2216                 }
2217         }
2218
2219         /*
2220          * This has to happen after we've potentially unshared the file
2221          * descriptor table (so that the pidfd doesn't leak into the child
2222          * if the fd table isn't shared).
2223          */
2224         if (clone_flags & CLONE_PIDFD) {
2225                 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2226                 if (retval < 0)
2227                         goto bad_fork_free_pid;
2228
2229                 pidfd = retval;
2230
2231                 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2232                                               O_RDWR | O_CLOEXEC);
2233                 if (IS_ERR(pidfile)) {
2234                         put_unused_fd(pidfd);
2235                         retval = PTR_ERR(pidfile);
2236                         goto bad_fork_free_pid;
2237                 }
2238                 get_pid(pid);   /* held by pidfile now */
2239
2240                 retval = put_user(pidfd, args->pidfd);
2241                 if (retval)
2242                         goto bad_fork_put_pidfd;
2243         }
2244
2245 #ifdef CONFIG_BLOCK
2246         p->plug = NULL;
2247 #endif
2248         futex_init_task(p);
2249
2250         /*
2251          * sigaltstack should be cleared when sharing the same VM
2252          */
2253         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2254                 sas_ss_reset(p);
2255
2256         /*
2257          * Syscall tracing and stepping should be turned off in the
2258          * child regardless of CLONE_PTRACE.
2259          */
2260         user_disable_single_step(p);
2261         clear_task_syscall_work(p, SYSCALL_TRACE);
2262 #if defined(CONFIG_GENERIC_ENTRY) || defined(TIF_SYSCALL_EMU)
2263         clear_task_syscall_work(p, SYSCALL_EMU);
2264 #endif
2265         clear_tsk_latency_tracing(p);
2266
2267         /* ok, now we should be set up.. */
2268         p->pid = pid_nr(pid);
2269         if (clone_flags & CLONE_THREAD) {
2270                 p->group_leader = current->group_leader;
2271                 p->tgid = current->tgid;
2272         } else {
2273                 p->group_leader = p;
2274                 p->tgid = p->pid;
2275         }
2276
2277         p->nr_dirtied = 0;
2278         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2279         p->dirty_paused_when = 0;
2280
2281         p->pdeath_signal = 0;
2282         INIT_LIST_HEAD(&p->thread_group);
2283         p->task_works = NULL;
2284
2285 #ifdef CONFIG_KRETPROBES
2286         p->kretprobe_instances.first = NULL;
2287 #endif
2288
2289         /*
2290          * Ensure that the cgroup subsystem policies allow the new process to be
2291          * forked. It should be noted that the new process's css_set can be changed
2292          * between here and cgroup_post_fork() if an organisation operation is in
2293          * progress.
2294          */
2295         retval = cgroup_can_fork(p, args);
2296         if (retval)
2297                 goto bad_fork_put_pidfd;
2298
2299         /*
2300          * From this point on we must avoid any synchronous user-space
2301          * communication until we take the tasklist-lock. In particular, we do
2302          * not want user-space to be able to predict the process start-time by
2303          * stalling fork(2) after we recorded the start_time but before it is
2304          * visible to the system.
2305          */
2306
2307         p->start_time = ktime_get_ns();
2308         p->start_boottime = ktime_get_boottime_ns();
2309
2310         /*
2311          * Make it visible to the rest of the system, but dont wake it up yet.
2312          * Need tasklist lock for parent etc handling!
2313          */
2314         write_lock_irq(&tasklist_lock);
2315
2316         /* CLONE_PARENT re-uses the old parent */
2317         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2318                 p->real_parent = current->real_parent;
2319                 p->parent_exec_id = current->parent_exec_id;
2320                 if (clone_flags & CLONE_THREAD)
2321                         p->exit_signal = -1;
2322                 else
2323                         p->exit_signal = current->group_leader->exit_signal;
2324         } else {
2325                 p->real_parent = current;
2326                 p->parent_exec_id = current->self_exec_id;
2327                 p->exit_signal = args->exit_signal;
2328         }
2329
2330         klp_copy_process(p);
2331
2332         sched_core_fork(p);
2333
2334         spin_lock(&current->sighand->siglock);
2335
2336         /*
2337          * Copy seccomp details explicitly here, in case they were changed
2338          * before holding sighand lock.
2339          */
2340         copy_seccomp(p);
2341
2342         rseq_fork(p, clone_flags);
2343
2344         /* Don't start children in a dying pid namespace */
2345         if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2346                 retval = -ENOMEM;
2347                 goto bad_fork_cancel_cgroup;
2348         }
2349
2350         /* Let kill terminate clone/fork in the middle */
2351         if (fatal_signal_pending(current)) {
2352                 retval = -EINTR;
2353                 goto bad_fork_cancel_cgroup;
2354         }
2355
2356         /* past the last point of failure */
2357         if (pidfile)
2358                 fd_install(pidfd, pidfile);
2359
2360         init_task_pid_links(p);
2361         if (likely(p->pid)) {
2362                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2363
2364                 init_task_pid(p, PIDTYPE_PID, pid);
2365                 if (thread_group_leader(p)) {
2366                         init_task_pid(p, PIDTYPE_TGID, pid);
2367                         init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2368                         init_task_pid(p, PIDTYPE_SID, task_session(current));
2369
2370                         if (is_child_reaper(pid)) {
2371                                 ns_of_pid(pid)->child_reaper = p;
2372                                 p->signal->flags |= SIGNAL_UNKILLABLE;
2373                         }
2374                         p->signal->shared_pending.signal = delayed.signal;
2375                         p->signal->tty = tty_kref_get(current->signal->tty);
2376                         /*
2377                          * Inherit has_child_subreaper flag under the same
2378                          * tasklist_lock with adding child to the process tree
2379                          * for propagate_has_child_subreaper optimization.
2380                          */
2381                         p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2382                                                          p->real_parent->signal->is_child_subreaper;
2383                         list_add_tail(&p->sibling, &p->real_parent->children);
2384                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
2385                         attach_pid(p, PIDTYPE_TGID);
2386                         attach_pid(p, PIDTYPE_PGID);
2387                         attach_pid(p, PIDTYPE_SID);
2388                         __this_cpu_inc(process_counts);
2389                 } else {
2390                         current->signal->nr_threads++;
2391                         atomic_inc(&current->signal->live);
2392                         refcount_inc(&current->signal->sigcnt);
2393                         task_join_group_stop(p);
2394                         list_add_tail_rcu(&p->thread_group,
2395                                           &p->group_leader->thread_group);
2396                         list_add_tail_rcu(&p->thread_node,
2397                                           &p->signal->thread_head);
2398                 }
2399                 attach_pid(p, PIDTYPE_PID);
2400                 nr_threads++;
2401         }
2402         total_forks++;
2403         hlist_del_init(&delayed.node);
2404         spin_unlock(&current->sighand->siglock);
2405         syscall_tracepoint_update(p);
2406         write_unlock_irq(&tasklist_lock);
2407
2408         proc_fork_connector(p);
2409         sched_post_fork(p);
2410         cgroup_post_fork(p, args);
2411         perf_event_fork(p);
2412
2413         trace_task_newtask(p, clone_flags);
2414         uprobe_copy_process(p, clone_flags);
2415
2416         copy_oom_score_adj(clone_flags, p);
2417
2418         return p;
2419
2420 bad_fork_cancel_cgroup:
2421         sched_core_free(p);
2422         spin_unlock(&current->sighand->siglock);
2423         write_unlock_irq(&tasklist_lock);
2424         cgroup_cancel_fork(p, args);
2425 bad_fork_put_pidfd:
2426         if (clone_flags & CLONE_PIDFD) {
2427                 fput(pidfile);
2428                 put_unused_fd(pidfd);
2429         }
2430 bad_fork_free_pid:
2431         if (pid != &init_struct_pid)
2432                 free_pid(pid);
2433 bad_fork_cleanup_thread:
2434         exit_thread(p);
2435 bad_fork_cleanup_io:
2436         if (p->io_context)
2437                 exit_io_context(p);
2438 bad_fork_cleanup_namespaces:
2439         exit_task_namespaces(p);
2440 bad_fork_cleanup_mm:
2441         if (p->mm) {
2442                 mm_clear_owner(p->mm, p);
2443                 mmput(p->mm);
2444         }
2445 bad_fork_cleanup_signal:
2446         if (!(clone_flags & CLONE_THREAD))
2447                 free_signal_struct(p->signal);
2448 bad_fork_cleanup_sighand:
2449         __cleanup_sighand(p->sighand);
2450 bad_fork_cleanup_fs:
2451         exit_fs(p); /* blocking */
2452 bad_fork_cleanup_files:
2453         exit_files(p); /* blocking */
2454 bad_fork_cleanup_semundo:
2455         exit_sem(p);
2456 bad_fork_cleanup_security:
2457         security_task_free(p);
2458 bad_fork_cleanup_audit:
2459         audit_free(p);
2460 bad_fork_cleanup_perf:
2461         perf_event_free_task(p);
2462 bad_fork_cleanup_policy:
2463         lockdep_free_task(p);
2464 #ifdef CONFIG_NUMA
2465         mpol_put(p->mempolicy);
2466 bad_fork_cleanup_threadgroup_lock:
2467 #endif
2468         delayacct_tsk_free(p);
2469 bad_fork_cleanup_count:
2470         dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
2471         exit_creds(p);
2472 bad_fork_free:
2473         WRITE_ONCE(p->__state, TASK_DEAD);
2474         put_task_stack(p);
2475         delayed_free_task(p);
2476 fork_out:
2477         spin_lock_irq(&current->sighand->siglock);
2478         hlist_del_init(&delayed.node);
2479         spin_unlock_irq(&current->sighand->siglock);
2480         return ERR_PTR(retval);
2481 }
2482
2483 static inline void init_idle_pids(struct task_struct *idle)
2484 {
2485         enum pid_type type;
2486
2487         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2488                 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2489                 init_task_pid(idle, type, &init_struct_pid);
2490         }
2491 }
2492
2493 struct task_struct * __init fork_idle(int cpu)
2494 {
2495         struct task_struct *task;
2496         struct kernel_clone_args args = {
2497                 .flags = CLONE_VM,
2498         };
2499
2500         task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2501         if (!IS_ERR(task)) {
2502                 init_idle_pids(task);
2503                 init_idle(task, cpu);
2504         }
2505
2506         return task;
2507 }
2508
2509 struct mm_struct *copy_init_mm(void)
2510 {
2511         return dup_mm(NULL, &init_mm);
2512 }
2513
2514 /*
2515  * This is like kernel_clone(), but shaved down and tailored to just
2516  * creating io_uring workers. It returns a created task, or an error pointer.
2517  * The returned task is inactive, and the caller must fire it up through
2518  * wake_up_new_task(p). All signals are blocked in the created task.
2519  */
2520 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
2521 {
2522         unsigned long flags = CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|
2523                                 CLONE_IO;
2524         struct kernel_clone_args args = {
2525                 .flags          = ((lower_32_bits(flags) | CLONE_VM |
2526                                     CLONE_UNTRACED) & ~CSIGNAL),
2527                 .exit_signal    = (lower_32_bits(flags) & CSIGNAL),
2528                 .stack          = (unsigned long)fn,
2529                 .stack_size     = (unsigned long)arg,
2530                 .io_thread      = 1,
2531         };
2532
2533         return copy_process(NULL, 0, node, &args);
2534 }
2535
2536 /*
2537  *  Ok, this is the main fork-routine.
2538  *
2539  * It copies the process, and if successful kick-starts
2540  * it and waits for it to finish using the VM if required.
2541  *
2542  * args->exit_signal is expected to be checked for sanity by the caller.
2543  */
2544 pid_t kernel_clone(struct kernel_clone_args *args)
2545 {
2546         u64 clone_flags = args->flags;
2547         struct completion vfork;
2548         struct pid *pid;
2549         struct task_struct *p;
2550         int trace = 0;
2551         pid_t nr;
2552
2553         /*
2554          * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
2555          * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
2556          * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
2557          * field in struct clone_args and it still doesn't make sense to have
2558          * them both point at the same memory location. Performing this check
2559          * here has the advantage that we don't need to have a separate helper
2560          * to check for legacy clone().
2561          */
2562         if ((args->flags & CLONE_PIDFD) &&
2563             (args->flags & CLONE_PARENT_SETTID) &&
2564             (args->pidfd == args->parent_tid))
2565                 return -EINVAL;
2566
2567         /*
2568          * Determine whether and which event to report to ptracer.  When
2569          * called from kernel_thread or CLONE_UNTRACED is explicitly
2570          * requested, no event is reported; otherwise, report if the event
2571          * for the type of forking is enabled.
2572          */
2573         if (!(clone_flags & CLONE_UNTRACED)) {
2574                 if (clone_flags & CLONE_VFORK)
2575                         trace = PTRACE_EVENT_VFORK;
2576                 else if (args->exit_signal != SIGCHLD)
2577                         trace = PTRACE_EVENT_CLONE;
2578                 else
2579                         trace = PTRACE_EVENT_FORK;
2580
2581                 if (likely(!ptrace_event_enabled(current, trace)))
2582                         trace = 0;
2583         }
2584
2585         p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2586         add_latent_entropy();
2587
2588         if (IS_ERR(p))
2589                 return PTR_ERR(p);
2590
2591         /*
2592          * Do this prior waking up the new thread - the thread pointer
2593          * might get invalid after that point, if the thread exits quickly.
2594          */
2595         trace_sched_process_fork(current, p);
2596
2597         pid = get_task_pid(p, PIDTYPE_PID);
2598         nr = pid_vnr(pid);
2599
2600         if (clone_flags & CLONE_PARENT_SETTID)
2601                 put_user(nr, args->parent_tid);
2602
2603         if (clone_flags & CLONE_VFORK) {
2604                 p->vfork_done = &vfork;
2605                 init_completion(&vfork);
2606                 get_task_struct(p);
2607         }
2608
2609         wake_up_new_task(p);
2610
2611         /* forking complete and child started to run, tell ptracer */
2612         if (unlikely(trace))
2613                 ptrace_event_pid(trace, pid);
2614
2615         if (clone_flags & CLONE_VFORK) {
2616                 if (!wait_for_vfork_done(p, &vfork))
2617                         ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2618         }
2619
2620         put_pid(pid);
2621         return nr;
2622 }
2623
2624 /*
2625  * Create a kernel thread.
2626  */
2627 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2628 {
2629         struct kernel_clone_args args = {
2630                 .flags          = ((lower_32_bits(flags) | CLONE_VM |
2631                                     CLONE_UNTRACED) & ~CSIGNAL),
2632                 .exit_signal    = (lower_32_bits(flags) & CSIGNAL),
2633                 .stack          = (unsigned long)fn,
2634                 .stack_size     = (unsigned long)arg,
2635         };
2636
2637         return kernel_clone(&args);
2638 }
2639
2640 #ifdef __ARCH_WANT_SYS_FORK
2641 SYSCALL_DEFINE0(fork)
2642 {
2643 #ifdef CONFIG_MMU
2644         struct kernel_clone_args args = {
2645                 .exit_signal = SIGCHLD,
2646         };
2647
2648         return kernel_clone(&args);
2649 #else
2650         /* can not support in nommu mode */
2651         return -EINVAL;
2652 #endif
2653 }
2654 #endif
2655
2656 #ifdef __ARCH_WANT_SYS_VFORK
2657 SYSCALL_DEFINE0(vfork)
2658 {
2659         struct kernel_clone_args args = {
2660                 .flags          = CLONE_VFORK | CLONE_VM,
2661                 .exit_signal    = SIGCHLD,
2662         };
2663
2664         return kernel_clone(&args);
2665 }
2666 #endif
2667
2668 #ifdef __ARCH_WANT_SYS_CLONE
2669 #ifdef CONFIG_CLONE_BACKWARDS
2670 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2671                  int __user *, parent_tidptr,
2672                  unsigned long, tls,
2673                  int __user *, child_tidptr)
2674 #elif defined(CONFIG_CLONE_BACKWARDS2)
2675 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2676                  int __user *, parent_tidptr,
2677                  int __user *, child_tidptr,
2678                  unsigned long, tls)
2679 #elif defined(CONFIG_CLONE_BACKWARDS3)
2680 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2681                 int, stack_size,
2682                 int __user *, parent_tidptr,
2683                 int __user *, child_tidptr,
2684                 unsigned long, tls)
2685 #else
2686 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2687                  int __user *, parent_tidptr,
2688                  int __user *, child_tidptr,
2689                  unsigned long, tls)
2690 #endif
2691 {
2692         struct kernel_clone_args args = {
2693                 .flags          = (lower_32_bits(clone_flags) & ~CSIGNAL),
2694                 .pidfd          = parent_tidptr,
2695                 .child_tid      = child_tidptr,
2696                 .parent_tid     = parent_tidptr,
2697                 .exit_signal    = (lower_32_bits(clone_flags) & CSIGNAL),
2698                 .stack          = newsp,
2699                 .tls            = tls,
2700         };
2701
2702         return kernel_clone(&args);
2703 }
2704 #endif
2705
2706 #ifdef __ARCH_WANT_SYS_CLONE3
2707
2708 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2709                                               struct clone_args __user *uargs,
2710                                               size_t usize)
2711 {
2712         int err;
2713         struct clone_args args;
2714         pid_t *kset_tid = kargs->set_tid;
2715
2716         BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
2717                      CLONE_ARGS_SIZE_VER0);
2718         BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
2719                      CLONE_ARGS_SIZE_VER1);
2720         BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
2721                      CLONE_ARGS_SIZE_VER2);
2722         BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
2723
2724         if (unlikely(usize > PAGE_SIZE))
2725                 return -E2BIG;
2726         if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
2727                 return -EINVAL;
2728
2729         err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
2730         if (err)
2731                 return err;
2732
2733         if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
2734                 return -EINVAL;
2735
2736         if (unlikely(!args.set_tid && args.set_tid_size > 0))
2737                 return -EINVAL;
2738
2739         if (unlikely(args.set_tid && args.set_tid_size == 0))
2740                 return -EINVAL;
2741
2742         /*
2743          * Verify that higher 32bits of exit_signal are unset and that
2744          * it is a valid signal
2745          */
2746         if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
2747                      !valid_signal(args.exit_signal)))
2748                 return -EINVAL;
2749
2750         if ((args.flags & CLONE_INTO_CGROUP) &&
2751             (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
2752                 return -EINVAL;
2753
2754         *kargs = (struct kernel_clone_args){
2755                 .flags          = args.flags,
2756                 .pidfd          = u64_to_user_ptr(args.pidfd),
2757                 .child_tid      = u64_to_user_ptr(args.child_tid),
2758                 .parent_tid     = u64_to_user_ptr(args.parent_tid),
2759                 .exit_signal    = args.exit_signal,
2760                 .stack          = args.stack,
2761                 .stack_size     = args.stack_size,
2762                 .tls            = args.tls,
2763                 .set_tid_size   = args.set_tid_size,
2764                 .cgroup         = args.cgroup,
2765         };
2766
2767         if (args.set_tid &&
2768                 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
2769                         (kargs->set_tid_size * sizeof(pid_t))))
2770                 return -EFAULT;
2771
2772         kargs->set_tid = kset_tid;
2773
2774         return 0;
2775 }
2776
2777 /**
2778  * clone3_stack_valid - check and prepare stack
2779  * @kargs: kernel clone args
2780  *
2781  * Verify that the stack arguments userspace gave us are sane.
2782  * In addition, set the stack direction for userspace since it's easy for us to
2783  * determine.
2784  */
2785 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
2786 {
2787         if (kargs->stack == 0) {
2788                 if (kargs->stack_size > 0)
2789                         return false;
2790         } else {
2791                 if (kargs->stack_size == 0)
2792                         return false;
2793
2794                 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
2795                         return false;
2796
2797 #if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
2798                 kargs->stack += kargs->stack_size;
2799 #endif
2800         }
2801
2802         return true;
2803 }
2804
2805 static bool clone3_args_valid(struct kernel_clone_args *kargs)
2806 {
2807         /* Verify that no unknown flags are passed along. */
2808         if (kargs->flags &
2809             ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
2810                 return false;
2811
2812         /*
2813          * - make the CLONE_DETACHED bit reusable for clone3
2814          * - make the CSIGNAL bits reusable for clone3
2815          */
2816         if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2817                 return false;
2818
2819         if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
2820             (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
2821                 return false;
2822
2823         if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2824             kargs->exit_signal)
2825                 return false;
2826
2827         if (!clone3_stack_valid(kargs))
2828                 return false;
2829
2830         return true;
2831 }
2832
2833 /**
2834  * clone3 - create a new process with specific properties
2835  * @uargs: argument structure
2836  * @size:  size of @uargs
2837  *
2838  * clone3() is the extensible successor to clone()/clone2().
2839  * It takes a struct as argument that is versioned by its size.
2840  *
2841  * Return: On success, a positive PID for the child process.
2842  *         On error, a negative errno number.
2843  */
2844 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2845 {
2846         int err;
2847
2848         struct kernel_clone_args kargs;
2849         pid_t set_tid[MAX_PID_NS_LEVEL];
2850
2851         kargs.set_tid = set_tid;
2852
2853         err = copy_clone_args_from_user(&kargs, uargs, size);
2854         if (err)
2855                 return err;
2856
2857         if (!clone3_args_valid(&kargs))
2858                 return -EINVAL;
2859
2860         return kernel_clone(&kargs);
2861 }
2862 #endif
2863
2864 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2865 {
2866         struct task_struct *leader, *parent, *child;
2867         int res;
2868
2869         read_lock(&tasklist_lock);
2870         leader = top = top->group_leader;
2871 down:
2872         for_each_thread(leader, parent) {
2873                 list_for_each_entry(child, &parent->children, sibling) {
2874                         res = visitor(child, data);
2875                         if (res) {
2876                                 if (res < 0)
2877                                         goto out;
2878                                 leader = child;
2879                                 goto down;
2880                         }
2881 up:
2882                         ;
2883                 }
2884         }
2885
2886         if (leader != top) {
2887                 child = leader;
2888                 parent = child->real_parent;
2889                 leader = parent->group_leader;
2890                 goto up;
2891         }
2892 out:
2893         read_unlock(&tasklist_lock);
2894 }
2895
2896 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2897 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2898 #endif
2899
2900 static void sighand_ctor(void *data)
2901 {
2902         struct sighand_struct *sighand = data;
2903
2904         spin_lock_init(&sighand->siglock);
2905         init_waitqueue_head(&sighand->signalfd_wqh);
2906 }
2907
2908 void __init proc_caches_init(void)
2909 {
2910         unsigned int mm_size;
2911
2912         sighand_cachep = kmem_cache_create("sighand_cache",
2913                         sizeof(struct sighand_struct), 0,
2914                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2915                         SLAB_ACCOUNT, sighand_ctor);
2916         signal_cachep = kmem_cache_create("signal_cache",
2917                         sizeof(struct signal_struct), 0,
2918                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2919                         NULL);
2920         files_cachep = kmem_cache_create("files_cache",
2921                         sizeof(struct files_struct), 0,
2922                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2923                         NULL);
2924         fs_cachep = kmem_cache_create("fs_cache",
2925                         sizeof(struct fs_struct), 0,
2926                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2927                         NULL);
2928
2929         /*
2930          * The mm_cpumask is located at the end of mm_struct, and is
2931          * dynamically sized based on the maximum CPU number this system
2932          * can have, taking hotplug into account (nr_cpu_ids).
2933          */
2934         mm_size = sizeof(struct mm_struct) + cpumask_size();
2935
2936         mm_cachep = kmem_cache_create_usercopy("mm_struct",
2937                         mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
2938                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2939                         offsetof(struct mm_struct, saved_auxv),
2940                         sizeof_field(struct mm_struct, saved_auxv),
2941                         NULL);
2942         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2943         mmap_init();
2944         nsproxy_cache_init();
2945 }
2946
2947 /*
2948  * Check constraints on flags passed to the unshare system call.
2949  */
2950 static int check_unshare_flags(unsigned long unshare_flags)
2951 {
2952         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2953                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2954                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2955                                 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP|
2956                                 CLONE_NEWTIME))
2957                 return -EINVAL;
2958         /*
2959          * Not implemented, but pretend it works if there is nothing
2960          * to unshare.  Note that unsharing the address space or the
2961          * signal handlers also need to unshare the signal queues (aka
2962          * CLONE_THREAD).
2963          */
2964         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2965                 if (!thread_group_empty(current))
2966                         return -EINVAL;
2967         }
2968         if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2969                 if (refcount_read(&current->sighand->count) > 1)
2970                         return -EINVAL;
2971         }
2972         if (unshare_flags & CLONE_VM) {
2973                 if (!current_is_single_threaded())
2974                         return -EINVAL;
2975         }
2976
2977         return 0;
2978 }
2979
2980 /*
2981  * Unshare the filesystem structure if it is being shared
2982  */
2983 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2984 {
2985         struct fs_struct *fs = current->fs;
2986
2987         if (!(unshare_flags & CLONE_FS) || !fs)
2988                 return 0;
2989
2990         /* don't need lock here; in the worst case we'll do useless copy */
2991         if (fs->users == 1)
2992                 return 0;
2993
2994         *new_fsp = copy_fs_struct(fs);
2995         if (!*new_fsp)
2996                 return -ENOMEM;
2997
2998         return 0;
2999 }
3000
3001 /*
3002  * Unshare file descriptor table if it is being shared
3003  */
3004 int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
3005                struct files_struct **new_fdp)
3006 {
3007         struct files_struct *fd = current->files;
3008         int error = 0;
3009
3010         if ((unshare_flags & CLONE_FILES) &&
3011             (fd && atomic_read(&fd->count) > 1)) {
3012                 *new_fdp = dup_fd(fd, max_fds, &error);
3013                 if (!*new_fdp)
3014                         return error;
3015         }
3016
3017         return 0;
3018 }
3019
3020 /*
3021  * unshare allows a process to 'unshare' part of the process
3022  * context which was originally shared using clone.  copy_*
3023  * functions used by kernel_clone() cannot be used here directly
3024  * because they modify an inactive task_struct that is being
3025  * constructed. Here we are modifying the current, active,
3026  * task_struct.
3027  */
3028 int ksys_unshare(unsigned long unshare_flags)
3029 {
3030         struct fs_struct *fs, *new_fs = NULL;
3031         struct files_struct *fd, *new_fd = NULL;
3032         struct cred *new_cred = NULL;
3033         struct nsproxy *new_nsproxy = NULL;
3034         int do_sysvsem = 0;
3035         int err;
3036
3037         /*
3038          * If unsharing a user namespace must also unshare the thread group
3039          * and unshare the filesystem root and working directories.
3040          */
3041         if (unshare_flags & CLONE_NEWUSER)
3042                 unshare_flags |= CLONE_THREAD | CLONE_FS;
3043         /*
3044          * If unsharing vm, must also unshare signal handlers.
3045          */
3046         if (unshare_flags & CLONE_VM)
3047                 unshare_flags |= CLONE_SIGHAND;
3048         /*
3049          * If unsharing a signal handlers, must also unshare the signal queues.
3050          */
3051         if (unshare_flags & CLONE_SIGHAND)
3052                 unshare_flags |= CLONE_THREAD;
3053         /*
3054          * If unsharing namespace, must also unshare filesystem information.
3055          */
3056         if (unshare_flags & CLONE_NEWNS)
3057                 unshare_flags |= CLONE_FS;
3058
3059         err = check_unshare_flags(unshare_flags);
3060         if (err)
3061                 goto bad_unshare_out;
3062         /*
3063          * CLONE_NEWIPC must also detach from the undolist: after switching
3064          * to a new ipc namespace, the semaphore arrays from the old
3065          * namespace are unreachable.
3066          */
3067         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
3068                 do_sysvsem = 1;
3069         err = unshare_fs(unshare_flags, &new_fs);
3070         if (err)
3071                 goto bad_unshare_out;
3072         err = unshare_fd(unshare_flags, NR_OPEN_MAX, &new_fd);
3073         if (err)
3074                 goto bad_unshare_cleanup_fs;
3075         err = unshare_userns(unshare_flags, &new_cred);
3076         if (err)
3077                 goto bad_unshare_cleanup_fd;
3078         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
3079                                          new_cred, new_fs);
3080         if (err)
3081                 goto bad_unshare_cleanup_cred;
3082
3083         if (new_cred) {
3084                 err = set_cred_ucounts(new_cred);
3085                 if (err)
3086                         goto bad_unshare_cleanup_cred;
3087         }
3088
3089         if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
3090                 if (do_sysvsem) {
3091                         /*
3092                          * CLONE_SYSVSEM is equivalent to sys_exit().
3093                          */
3094                         exit_sem(current);
3095                 }
3096                 if (unshare_flags & CLONE_NEWIPC) {
3097                         /* Orphan segments in old ns (see sem above). */
3098                         exit_shm(current);
3099                         shm_init_task(current);
3100                 }
3101
3102                 if (new_nsproxy)
3103                         switch_task_namespaces(current, new_nsproxy);
3104
3105                 task_lock(current);
3106
3107                 if (new_fs) {
3108                         fs = current->fs;
3109                         spin_lock(&fs->lock);
3110                         current->fs = new_fs;
3111                         if (--fs->users)
3112                                 new_fs = NULL;
3113                         else
3114                                 new_fs = fs;
3115                         spin_unlock(&fs->lock);
3116                 }
3117
3118                 if (new_fd) {
3119                         fd = current->files;
3120                         current->files = new_fd;
3121                         new_fd = fd;
3122                 }
3123
3124                 task_unlock(current);
3125
3126                 if (new_cred) {
3127                         /* Install the new user namespace */
3128                         commit_creds(new_cred);
3129                         new_cred = NULL;
3130                 }
3131         }
3132
3133         perf_event_namespaces(current);
3134
3135 bad_unshare_cleanup_cred:
3136         if (new_cred)
3137                 put_cred(new_cred);
3138 bad_unshare_cleanup_fd:
3139         if (new_fd)
3140                 put_files_struct(new_fd);
3141
3142 bad_unshare_cleanup_fs:
3143         if (new_fs)
3144                 free_fs_struct(new_fs);
3145
3146 bad_unshare_out:
3147         return err;
3148 }
3149
3150 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
3151 {
3152         return ksys_unshare(unshare_flags);
3153 }
3154
3155 /*
3156  *      Helper to unshare the files of the current task.
3157  *      We don't want to expose copy_files internals to
3158  *      the exec layer of the kernel.
3159  */
3160
3161 int unshare_files(void)
3162 {
3163         struct task_struct *task = current;
3164         struct files_struct *old, *copy = NULL;
3165         int error;
3166
3167         error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, &copy);
3168         if (error || !copy)
3169                 return error;
3170
3171         old = task->files;
3172         task_lock(task);
3173         task->files = copy;
3174         task_unlock(task);
3175         put_files_struct(old);
3176         return 0;
3177 }
3178
3179 int sysctl_max_threads(struct ctl_table *table, int write,
3180                        void *buffer, size_t *lenp, loff_t *ppos)
3181 {
3182         struct ctl_table t;
3183         int ret;
3184         int threads = max_threads;
3185         int min = 1;
3186         int max = MAX_THREADS;
3187
3188         t = *table;
3189         t.data = &threads;
3190         t.extra1 = &min;
3191         t.extra2 = &max;
3192
3193         ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3194         if (ret || !write)
3195                 return ret;
3196
3197         max_threads = threads;
3198
3199         return 0;
3200 }