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