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