kernel/fork.c

   1 /*
   2  *  linux/kernel/fork.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  *  'fork.c' contains the help-routines for the 'fork' system call
   9  * (see also entry.S and others).
  10  * Fork is rather simple, once you get the hang of it, but the memory
  11  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
  12  */
  13
  14 #include <linux/slab.h>
  15 #include <linux/sched/autogroup.h>
  16 #include <linux/sched/mm.h>
  17 #include <linux/sched/coredump.h>
  18 #include <linux/sched/user.h>
  19 #include <linux/sched/numa_balancing.h>
  20 #include <linux/sched/stat.h>
  21 #include <linux/sched/task.h>
  22 #include <linux/sched/task_stack.h>
  23 #include <linux/sched/cputime.h>
  24 #include <linux/rtmutex.h>
  25 #include <linux/init.h>
  26 #include <linux/unistd.h>
  27 #include <linux/module.h>
  28 #include <linux/vmalloc.h>
  29 #include <linux/completion.h>
  30 #include <linux/personality.h>
  31 #include <linux/mempolicy.h>
  32 #include <linux/sem.h>
  33 #include <linux/file.h>
  34 #include <linux/fdtable.h>
  35 #include <linux/iocontext.h>
  36 #include <linux/key.h>
  37 #include <linux/binfmts.h>
  38 #include <linux/mman.h>
  39 #include <linux/mmu_notifier.h>
  40 #include <linux/fs.h>
  41 #include <linux/mm.h>
  42 #include <linux/vmacache.h>
  43 #include <linux/nsproxy.h>
  44 #include <linux/capability.h>
  45 #include <linux/cpu.h>
  46 #include <linux/cgroup.h>
  47 #include <linux/security.h>
  48 #include <linux/hugetlb.h>
  49 #include <linux/seccomp.h>
  50 #include <linux/swap.h>
  51 #include <linux/syscalls.h>
  52 #include <linux/jiffies.h>
  53 #include <linux/futex.h>
  54 #include <linux/compat.h>
  55 #include <linux/kthread.h>
  56 #include <linux/task_io_accounting_ops.h>
  57 #include <linux/rcupdate.h>
  58 #include <linux/ptrace.h>
  59 #include <linux/mount.h>
  60 #include <linux/audit.h>
  61 #include <linux/memcontrol.h>
  62 #include <linux/ftrace.h>
  63 #include <linux/proc_fs.h>
  64 #include <linux/profile.h>
  65 #include <linux/rmap.h>
  66 #include <linux/ksm.h>
  67 #include <linux/acct.h>
  68 #include <linux/userfaultfd_k.h>
  69 #include <linux/tsacct_kern.h>
  70 #include <linux/cn_proc.h>
  71 #include <linux/freezer.h>
  72 #include <linux/delayacct.h>
  73 #include <linux/taskstats_kern.h>
  74 #include <linux/random.h>
  75 #include <linux/tty.h>
  76 #include <linux/blkdev.h>
  77 #include <linux/fs_struct.h>
  78 #include <linux/magic.h>
  79 #include <linux/perf_event.h>
  80 #include <linux/posix-timers.h>
  81 #include <linux/user-return-notifier.h>
  82 #include <linux/oom.h>
  83 #include <linux/khugepaged.h>
  84 #include <linux/signalfd.h>
  85 #include <linux/uprobes.h>
  86 #include <linux/aio.h>
  87 #include <linux/compiler.h>
  88 #include <linux/sysctl.h>
  89 #include <linux/kcov.h>
  90 #include <linux/livepatch.h>
  91
  92 #include <asm/pgtable.h>
  93 #include <asm/pgalloc.h>
  94 #include <linux/uaccess.h>
  95 #include <asm/mmu_context.h>
  96 #include <asm/cacheflush.h>
  97 #include <asm/tlbflush.h>
  98
  99 #include <trace/events/sched.h>
 100
 101 #define CREATE_TRACE_POINTS
 102 #include <trace/events/task.h>
 103
 104 /*
 105  * Minimum number of threads to boot the kernel
 106  */
 107 #define MIN_THREADS 20
 108
 109 /*
 110  * Maximum number of threads
 111  */
 112 #define MAX_THREADS FUTEX_TID_MASK
 113
 114 /*
 115  * Protected counters by write_lock_irq(&tasklist_lock)
 116  */
 117 unsigned long total_forks;      /* Handle normal Linux uptimes. */
 118 int nr_threads;                 /* The idle threads do not count.. */
 119
 120 int max_threads;                /* tunable limit on nr_threads */
 121
 122 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
 123
 124 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
 125
 126 #ifdef CONFIG_PROVE_RCU
 127 int lockdep_tasklist_lock_is_held(void)
 128 {
 129         return lockdep_is_held(&tasklist_lock);
 130 }
 131 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
 132 #endif /* #ifdef CONFIG_PROVE_RCU */
 133
 134 int nr_processes(void)
 135 {
 136         int cpu;
 137         int total = 0;
 138
 139         for_each_possible_cpu(cpu)
 140                 total += per_cpu(process_counts, cpu);
 141
 142         return total;
 143 }
 144
 145 void __weak arch_release_task_struct(struct task_struct *tsk)
 146 {
 147 }
 148
 149 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 150 static struct kmem_cache *task_struct_cachep;
 151
 152 static inline struct task_struct *alloc_task_struct_node(int node)
 153 {
 154         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
 155 }
 156
 157 static inline void free_task_struct(struct task_struct *tsk)
 158 {
 159         kmem_cache_free(task_struct_cachep, tsk);
 160 }
 161 #endif
 162
 163 void __weak arch_release_thread_stack(unsigned long *stack)
 164 {
 165 }
 166
 167 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
 168
 169 /*
 170  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
 171  * kmemcache based allocator.
 172  */
 173 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
 174
 175 #ifdef CONFIG_VMAP_STACK
 176 /*
 177  * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
 178  * flush.  Try to minimize the number of calls by caching stacks.
 179  */
 180 #define NR_CACHED_STACKS 2
 181 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
 182
 183 static int free_vm_stack_cache(unsigned int cpu)
 184 {
 185         struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
 186         int i;
 187
 188         for (i = 0; i < NR_CACHED_STACKS; i++) {
 189                 struct vm_struct *vm_stack = cached_vm_stacks[i];
 190
 191                 if (!vm_stack)
 192                         continue;
 193
 194                 vfree(vm_stack->addr);
 195                 cached_vm_stacks[i] = NULL;
 196         }
 197
 198         return 0;
 199 }
 200 #endif
 201
 202 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
 203 {
 204 #ifdef CONFIG_VMAP_STACK
 205         void *stack;
 206         int i;
 207
 208         for (i = 0; i < NR_CACHED_STACKS; i++) {
 209                 struct vm_struct *s;
 210
 211                 s = this_cpu_xchg(cached_stacks[i], NULL);
 212
 213                 if (!s)
 214                         continue;
 215
 216                 tsk->stack_vm_area = s;
 217                 return s->addr;
 218         }
 219
 220         stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE,
 221                                      VMALLOC_START, VMALLOC_END,
 222                                      THREADINFO_GFP,
 223                                      PAGE_KERNEL,
 224                                      0, node, __builtin_return_address(0));
 225
 226         /*
 227          * We can't call find_vm_area() in interrupt context, and
 228          * free_thread_stack() can be called in interrupt context,
 229          * so cache the vm_struct.
 230          */
 231         if (stack)
 232                 tsk->stack_vm_area = find_vm_area(stack);
 233         return stack;
 234 #else
 235         struct page *page = alloc_pages_node(node, THREADINFO_GFP,
 236                                              THREAD_SIZE_ORDER);
 237
 238         return page ? page_address(page) : NULL;
 239 #endif
 240 }
 241
 242 static inline void free_thread_stack(struct task_struct *tsk)
 243 {
 244 #ifdef CONFIG_VMAP_STACK
 245         if (task_stack_vm_area(tsk)) {
 246                 int i;
 247
 248                 for (i = 0; i < NR_CACHED_STACKS; i++) {
 249                         if (this_cpu_cmpxchg(cached_stacks[i],
 250                                         NULL, tsk->stack_vm_area) != NULL)
 251                                 continue;
 252
 253                         return;
 254                 }
 255
 256                 vfree_atomic(tsk->stack);
 257                 return;
 258         }
 259 #endif
 260
 261         __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
 262 }
 263 # else
 264 static struct kmem_cache *thread_stack_cache;
 265
 266 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
 267                                                   int node)
 268 {
 269         return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
 270 }
 271
 272 static void free_thread_stack(struct task_struct *tsk)
 273 {
 274         kmem_cache_free(thread_stack_cache, tsk->stack);
 275 }
 276
 277 void thread_stack_cache_init(void)
 278 {
 279         thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE,
 280                                               THREAD_SIZE, 0, NULL);
 281         BUG_ON(thread_stack_cache == NULL);
 282 }
 283 # endif
 284 #endif
 285
 286 /* SLAB cache for signal_struct structures (tsk->signal) */
 287 static struct kmem_cache *signal_cachep;
 288
 289 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 290 struct kmem_cache *sighand_cachep;
 291
 292 /* SLAB cache for files_struct structures (tsk->files) */
 293 struct kmem_cache *files_cachep;
 294
 295 /* SLAB cache for fs_struct structures (tsk->fs) */
 296 struct kmem_cache *fs_cachep;
 297
 298 /* SLAB cache for vm_area_struct structures */
 299 struct kmem_cache *vm_area_cachep;
 300
 301 /* SLAB cache for mm_struct structures (tsk->mm) */
 302 static struct kmem_cache *mm_cachep;
 303
 304 static void account_kernel_stack(struct task_struct *tsk, int account)
 305 {
 306         void *stack = task_stack_page(tsk);
 307         struct vm_struct *vm = task_stack_vm_area(tsk);
 308
 309         BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
 310
 311         if (vm) {
 312                 int i;
 313
 314                 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
 315
 316                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
 317                         mod_zone_page_state(page_zone(vm->pages[i]),
 318                                             NR_KERNEL_STACK_KB,
 319                                             PAGE_SIZE / 1024 * account);
 320                 }
 321
 322                 /* All stack pages belong to the same memcg. */
 323                 mod_memcg_page_state(vm->pages[0], MEMCG_KERNEL_STACK_KB,
 324                                      account * (THREAD_SIZE / 1024));
 325         } else {
 326                 /*
 327                  * All stack pages are in the same zone and belong to the
 328                  * same memcg.
 329                  */
 330                 struct page *first_page = virt_to_page(stack);
 331
 332                 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
 333                                     THREAD_SIZE / 1024 * account);
 334
 335                 mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB,
 336                                      account * (THREAD_SIZE / 1024));
 337         }
 338 }
 339
 340 static void release_task_stack(struct task_struct *tsk)
 341 {
 342         if (WARN_ON(tsk->state != TASK_DEAD))
 343                 return;  /* Better to leak the stack than to free prematurely */
 344
 345         account_kernel_stack(tsk, -1);
 346         arch_release_thread_stack(tsk->stack);
 347         free_thread_stack(tsk);
 348         tsk->stack = NULL;
 349 #ifdef CONFIG_VMAP_STACK
 350         tsk->stack_vm_area = NULL;
 351 #endif
 352 }
 353
 354 #ifdef CONFIG_THREAD_INFO_IN_TASK
 355 void put_task_stack(struct task_struct *tsk)
 356 {
 357         if (atomic_dec_and_test(&tsk->stack_refcount))
 358                 release_task_stack(tsk);
 359 }
 360 #endif
 361
 362 void free_task(struct task_struct *tsk)
 363 {
 364 #ifndef CONFIG_THREAD_INFO_IN_TASK
 365         /*
 366          * The task is finally done with both the stack and thread_info,
 367          * so free both.
 368          */
 369         release_task_stack(tsk);
 370 #else
 371         /*
 372          * If the task had a separate stack allocation, it should be gone
 373          * by now.
 374          */
 375         WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0);
 376 #endif
 377         rt_mutex_debug_task_free(tsk);
 378         ftrace_graph_exit_task(tsk);
 379         put_seccomp_filter(tsk);
 380         arch_release_task_struct(tsk);
 381         if (tsk->flags & PF_KTHREAD)
 382                 free_kthread_struct(tsk);
 383         free_task_struct(tsk);
 384 }
 385 EXPORT_SYMBOL(free_task);
 386
 387 static inline void free_signal_struct(struct signal_struct *sig)
 388 {
 389         taskstats_tgid_free(sig);
 390         sched_autogroup_exit(sig);
 391         /*
 392          * __mmdrop is not safe to call from softirq context on x86 due to
 393          * pgd_dtor so postpone it to the async context
 394          */
 395         if (sig->oom_mm)
 396                 mmdrop_async(sig->oom_mm);
 397         kmem_cache_free(signal_cachep, sig);
 398 }
 399
 400 static inline void put_signal_struct(struct signal_struct *sig)
 401 {
 402         if (atomic_dec_and_test(&sig->sigcnt))
 403                 free_signal_struct(sig);
 404 }
 405
 406 void __put_task_struct(struct task_struct *tsk)
 407 {
 408         WARN_ON(!tsk->exit_state);
 409         WARN_ON(atomic_read(&tsk->usage));
 410         WARN_ON(tsk == current);
 411
 412         cgroup_free(tsk);
 413         task_numa_free(tsk);
 414         security_task_free(tsk);
 415         exit_creds(tsk);
 416         delayacct_tsk_free(tsk);
 417         put_signal_struct(tsk->signal);
 418
 419         if (!profile_handoff_task(tsk))
 420                 free_task(tsk);
 421 }
 422 EXPORT_SYMBOL_GPL(__put_task_struct);
 423
 424 void __init __weak arch_task_cache_init(void) { }
 425
 426 /*
 427  * set_max_threads
 428  */
 429 static void set_max_threads(unsigned int max_threads_suggested)
 430 {
 431         u64 threads;
 432
 433         /*
 434          * The number of threads shall be limited such that the thread
 435          * structures may only consume a small part of the available memory.
 436          */
 437         if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
 438                 threads = MAX_THREADS;
 439         else
 440                 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
 441                                     (u64) THREAD_SIZE * 8UL);
 442
 443         if (threads > max_threads_suggested)
 444                 threads = max_threads_suggested;
 445
 446         max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
 447 }
 448
 449 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
 450 /* Initialized by the architecture: */
 451 int arch_task_struct_size __read_mostly;
 452 #endif
 453
 454 void __init fork_init(void)
 455 {
 456         int i;
 457 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 458 #ifndef ARCH_MIN_TASKALIGN
 459 #define ARCH_MIN_TASKALIGN      0
 460 #endif
 461         int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
 462
 463         /* create a slab on which task_structs can be allocated */
 464         task_struct_cachep = kmem_cache_create("task_struct",
 465                         arch_task_struct_size, align,
 466                         SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL);
 467 #endif
 468
 469         /* do the arch specific task caches init */
 470         arch_task_cache_init();
 471
 472         set_max_threads(MAX_THREADS);
 473
 474         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 475         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 476         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 477                 init_task.signal->rlim[RLIMIT_NPROC];
 478
 479         for (i = 0; i < UCOUNT_COUNTS; i++) {
 480                 init_user_ns.ucount_max[i] = max_threads/2;
 481         }
 482
 483 #ifdef CONFIG_VMAP_STACK
 484         cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
 485                           NULL, free_vm_stack_cache);
 486 #endif
 487 }
 488
 489 int __weak arch_dup_task_struct(struct task_struct *dst,
 490                                                struct task_struct *src)
 491 {
 492         *dst = *src;
 493         return 0;
 494 }
 495
 496 void set_task_stack_end_magic(struct task_struct *tsk)
 497 {
 498         unsigned long *stackend;
 499
 500         stackend = end_of_stack(tsk);
 501         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 502 }
 503
 504 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 505 {
 506         struct task_struct *tsk;
 507         unsigned long *stack;
 508         struct vm_struct *stack_vm_area;
 509         int err;
 510
 511         if (node == NUMA_NO_NODE)
 512                 node = tsk_fork_get_node(orig);
 513         tsk = alloc_task_struct_node(node);
 514         if (!tsk)
 515                 return NULL;
 516
 517         stack = alloc_thread_stack_node(tsk, node);
 518         if (!stack)
 519                 goto free_tsk;
 520
 521         stack_vm_area = task_stack_vm_area(tsk);
 522
 523         err = arch_dup_task_struct(tsk, orig);
 524
 525         /*
 526          * arch_dup_task_struct() clobbers the stack-related fields.  Make
 527          * sure they're properly initialized before using any stack-related
 528          * functions again.
 529          */
 530         tsk->stack = stack;
 531 #ifdef CONFIG_VMAP_STACK
 532         tsk->stack_vm_area = stack_vm_area;
 533 #endif
 534 #ifdef CONFIG_THREAD_INFO_IN_TASK
 535         atomic_set(&tsk->stack_refcount, 1);
 536 #endif
 537
 538         if (err)
 539                 goto free_stack;
 540
 541 #ifdef CONFIG_SECCOMP
 542         /*
 543          * We must handle setting up seccomp filters once we're under
 544          * the sighand lock in case orig has changed between now and
 545          * then. Until then, filter must be NULL to avoid messing up
 546          * the usage counts on the error path calling free_task.
 547          */
 548         tsk->seccomp.filter = NULL;
 549 #endif
 550
 551         setup_thread_stack(tsk, orig);
 552         clear_user_return_notifier(tsk);
 553         clear_tsk_need_resched(tsk);
 554         set_task_stack_end_magic(tsk);
 555
 556 #ifdef CONFIG_CC_STACKPROTECTOR
 557         tsk->stack_canary = get_random_canary();
 558 #endif
 559
 560         /*
 561          * One for us, one for whoever does the "release_task()" (usually
 562          * parent)
 563          */
 564         atomic_set(&tsk->usage, 2);
 565 #ifdef CONFIG_BLK_DEV_IO_TRACE
 566         tsk->btrace_seq = 0;
 567 #endif
 568         tsk->splice_pipe = NULL;
 569         tsk->task_frag.page = NULL;
 570         tsk->wake_q.next = NULL;
 571
 572         account_kernel_stack(tsk, 1);
 573
 574         kcov_task_init(tsk);
 575
 576 #ifdef CONFIG_FAULT_INJECTION
 577         tsk->fail_nth = 0;
 578 #endif
 579
 580         return tsk;
 581
 582 free_stack:
 583         free_thread_stack(tsk);
 584 free_tsk:
 585         free_task_struct(tsk);
 586         return NULL;
 587 }
 588
 589 #ifdef CONFIG_MMU
 590 static __latent_entropy int dup_mmap(struct mm_struct *mm,
 591                                         struct mm_struct *oldmm)
 592 {
 593         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 594         struct rb_node **rb_link, *rb_parent;
 595         int retval;
 596         unsigned long charge;
 597         LIST_HEAD(uf);
 598
 599         uprobe_start_dup_mmap();
 600         if (down_write_killable(&oldmm->mmap_sem)) {
 601                 retval = -EINTR;
 602                 goto fail_uprobe_end;
 603         }
 604         flush_cache_dup_mm(oldmm);
 605         uprobe_dup_mmap(oldmm, mm);
 606         /*
 607          * Not linked in yet - no deadlock potential:
 608          */
 609         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 610
 611         /* No ordering required: file already has been exposed. */
 612         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
 613
 614         mm->total_vm = oldmm->total_vm;
 615         mm->data_vm = oldmm->data_vm;
 616         mm->exec_vm = oldmm->exec_vm;
 617         mm->stack_vm = oldmm->stack_vm;
 618
 619         rb_link = &mm->mm_rb.rb_node;
 620         rb_parent = NULL;
 621         pprev = &mm->mmap;
 622         retval = ksm_fork(mm, oldmm);
 623         if (retval)
 624                 goto out;
 625         retval = khugepaged_fork(mm, oldmm);
 626         if (retval)
 627                 goto out;
 628
 629         prev = NULL;
 630         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 631                 struct file *file;
 632
 633                 if (mpnt->vm_flags & VM_DONTCOPY) {
 634                         vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
 635                         continue;
 636                 }
 637                 charge = 0;
 638                 if (mpnt->vm_flags & VM_ACCOUNT) {
 639                         unsigned long len = vma_pages(mpnt);
 640
 641                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
 642                                 goto fail_nomem;
 643                         charge = len;
 644                 }
 645                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 646                 if (!tmp)
 647                         goto fail_nomem;
 648                 *tmp = *mpnt;
 649                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
 650                 retval = vma_dup_policy(mpnt, tmp);
 651                 if (retval)
 652                         goto fail_nomem_policy;
 653                 tmp->vm_mm = mm;
 654                 retval = dup_userfaultfd(tmp, &uf);
 655                 if (retval)
 656                         goto fail_nomem_anon_vma_fork;
 657                 if (anon_vma_fork(tmp, mpnt))
 658                         goto fail_nomem_anon_vma_fork;
 659                 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
 660                 tmp->vm_next = tmp->vm_prev = NULL;
 661                 file = tmp->vm_file;
 662                 if (file) {
 663                         struct inode *inode = file_inode(file);
 664                         struct address_space *mapping = file->f_mapping;
 665
 666                         get_file(file);
 667                         if (tmp->vm_flags & VM_DENYWRITE)
 668                                 atomic_dec(&inode->i_writecount);
 669                         i_mmap_lock_write(mapping);
 670                         if (tmp->vm_flags & VM_SHARED)
 671                                 atomic_inc(&mapping->i_mmap_writable);
 672                         flush_dcache_mmap_lock(mapping);
 673                         /* insert tmp into the share list, just after mpnt */
 674                         vma_interval_tree_insert_after(tmp, mpnt,
 675                                         &mapping->i_mmap);
 676                         flush_dcache_mmap_unlock(mapping);
 677                         i_mmap_unlock_write(mapping);
 678                 }
 679
 680                 /*
 681                  * Clear hugetlb-related page reserves for children. This only
 682                  * affects MAP_PRIVATE mappings. Faults generated by the child
 683                  * are not guaranteed to succeed, even if read-only
 684                  */
 685                 if (is_vm_hugetlb_page(tmp))
 686                         reset_vma_resv_huge_pages(tmp);
 687
 688                 /*
 689                  * Link in the new vma and copy the page table entries.
 690                  */
 691                 *pprev = tmp;
 692                 pprev = &tmp->vm_next;
 693                 tmp->vm_prev = prev;
 694                 prev = tmp;
 695
 696                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 697                 rb_link = &tmp->vm_rb.rb_right;
 698                 rb_parent = &tmp->vm_rb;
 699
 700                 mm->map_count++;
 701                 retval = copy_page_range(mm, oldmm, mpnt);
 702
 703                 if (tmp->vm_ops && tmp->vm_ops->open)
 704                         tmp->vm_ops->open(tmp);
 705
 706                 if (retval)
 707                         goto out;
 708         }
 709         /* a new mm has just been created */
 710         arch_dup_mmap(oldmm, mm);
 711         retval = 0;
 712 out:
 713         up_write(&mm->mmap_sem);
 714         flush_tlb_mm(oldmm);
 715         up_write(&oldmm->mmap_sem);
 716         dup_userfaultfd_complete(&uf);
 717 fail_uprobe_end:
 718         uprobe_end_dup_mmap();
 719         return retval;
 720 fail_nomem_anon_vma_fork:
 721         mpol_put(vma_policy(tmp));
 722 fail_nomem_policy:
 723         kmem_cache_free(vm_area_cachep, tmp);
 724 fail_nomem:
 725         retval = -ENOMEM;
 726         vm_unacct_memory(charge);
 727         goto out;
 728 }
 729
 730 static inline int mm_alloc_pgd(struct mm_struct *mm)
 731 {
 732         mm->pgd = pgd_alloc(mm);
 733         if (unlikely(!mm->pgd))
 734                 return -ENOMEM;
 735         return 0;
 736 }
 737
 738 static inline void mm_free_pgd(struct mm_struct *mm)
 739 {
 740         pgd_free(mm, mm->pgd);
 741 }
 742 #else
 743 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 744 {
 745         down_write(&oldmm->mmap_sem);
 746         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
 747         up_write(&oldmm->mmap_sem);
 748         return 0;
 749 }
 750 #define mm_alloc_pgd(mm)        (0)
 751 #define mm_free_pgd(mm)
 752 #endif /* CONFIG_MMU */
 753
 754 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 755
 756 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 757 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 758
 759 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 760
 761 static int __init coredump_filter_setup(char *s)
 762 {
 763         default_dump_filter =
 764                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 765                 MMF_DUMP_FILTER_MASK;
 766         return 1;
 767 }
 768
 769 __setup("coredump_filter=", coredump_filter_setup);
 770
 771 #include <linux/init_task.h>
 772
 773 static void mm_init_aio(struct mm_struct *mm)
 774 {
 775 #ifdef CONFIG_AIO
 776         spin_lock_init(&mm->ioctx_lock);
 777         mm->ioctx_table = NULL;
 778 #endif
 779 }
 780
 781 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 782 {
 783 #ifdef CONFIG_MEMCG
 784         mm->owner = p;
 785 #endif
 786 }
 787
 788 static void mm_init_uprobes_state(struct mm_struct *mm)
 789 {
 790 #ifdef CONFIG_UPROBES
 791         mm->uprobes_state.xol_area = NULL;
 792 #endif
 793 }
 794
 795 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
 796         struct user_namespace *user_ns)
 797 {
 798         mm->mmap = NULL;
 799         mm->mm_rb = RB_ROOT;
 800         mm->vmacache_seqnum = 0;
 801         atomic_set(&mm->mm_users, 1);
 802         atomic_set(&mm->mm_count, 1);
 803         init_rwsem(&mm->mmap_sem);
 804         INIT_LIST_HEAD(&mm->mmlist);
 805         mm->core_state = NULL;
 806         atomic_long_set(&mm->nr_ptes, 0);
 807         mm_nr_pmds_init(mm);
 808         mm->map_count = 0;
 809         mm->locked_vm = 0;
 810         mm->pinned_vm = 0;
 811         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 812         spin_lock_init(&mm->page_table_lock);
 813         mm_init_cpumask(mm);
 814         mm_init_aio(mm);
 815         mm_init_owner(mm, p);
 816         RCU_INIT_POINTER(mm->exe_file, NULL);
 817         mmu_notifier_mm_init(mm);
 818         init_tlb_flush_pending(mm);
 819 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 820         mm->pmd_huge_pte = NULL;
 821 #endif
 822         mm_init_uprobes_state(mm);
 823
 824         if (current->mm) {
 825                 mm->flags = current->mm->flags & MMF_INIT_MASK;
 826                 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
 827         } else {
 828                 mm->flags = default_dump_filter;
 829                 mm->def_flags = 0;
 830         }
 831
 832         if (mm_alloc_pgd(mm))
 833                 goto fail_nopgd;
 834
 835         if (init_new_context(p, mm))
 836                 goto fail_nocontext;
 837
 838         mm->user_ns = get_user_ns(user_ns);
 839         return mm;
 840
 841 fail_nocontext:
 842         mm_free_pgd(mm);
 843 fail_nopgd:
 844         free_mm(mm);
 845         return NULL;
 846 }
 847
 848 static void check_mm(struct mm_struct *mm)
 849 {
 850         int i;
 851
 852         for (i = 0; i < NR_MM_COUNTERS; i++) {
 853                 long x = atomic_long_read(&mm->rss_stat.count[i]);
 854
 855                 if (unlikely(x))
 856                         printk(KERN_ALERT "BUG: Bad rss-counter state "
 857                                           "mm:%p idx:%d val:%ld\n", mm, i, x);
 858         }
 859
 860         if (atomic_long_read(&mm->nr_ptes))
 861                 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
 862                                 atomic_long_read(&mm->nr_ptes));
 863         if (mm_nr_pmds(mm))
 864                 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
 865                                 mm_nr_pmds(mm));
 866
 867 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 868         VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
 869 #endif
 870 }
 871
 872 /*
 873  * Allocate and initialize an mm_struct.
 874  */
 875 struct mm_struct *mm_alloc(void)
 876 {
 877         struct mm_struct *mm;
 878
 879         mm = allocate_mm();
 880         if (!mm)
 881                 return NULL;
 882
 883         memset(mm, 0, sizeof(*mm));
 884         return mm_init(mm, current, current_user_ns());
 885 }
 886
 887 /*
 888  * Called when the last reference to the mm
 889  * is dropped: either by a lazy thread or by
 890  * mmput. Free the page directory and the mm.
 891  */
 892 void __mmdrop(struct mm_struct *mm)
 893 {
 894         BUG_ON(mm == &init_mm);
 895         mm_free_pgd(mm);
 896         destroy_context(mm);
 897         mmu_notifier_mm_destroy(mm);
 898         check_mm(mm);
 899         put_user_ns(mm->user_ns);
 900         free_mm(mm);
 901 }
 902 EXPORT_SYMBOL_GPL(__mmdrop);
 903
 904 static inline void __mmput(struct mm_struct *mm)
 905 {
 906         VM_BUG_ON(atomic_read(&mm->mm_users));
 907
 908         uprobe_clear_state(mm);
 909         exit_aio(mm);
 910         ksm_exit(mm);
 911         khugepaged_exit(mm); /* must run before exit_mmap */
 912         exit_mmap(mm);
 913         mm_put_huge_zero_page(mm);
 914         set_mm_exe_file(mm, NULL);
 915         if (!list_empty(&mm->mmlist)) {
 916                 spin_lock(&mmlist_lock);
 917                 list_del(&mm->mmlist);
 918                 spin_unlock(&mmlist_lock);
 919         }
 920         if (mm->binfmt)
 921                 module_put(mm->binfmt->module);
 922         set_bit(MMF_OOM_SKIP, &mm->flags);
 923         mmdrop(mm);
 924 }
 925
 926 /*
 927  * Decrement the use count and release all resources for an mm.
 928  */
 929 void mmput(struct mm_struct *mm)
 930 {
 931         might_sleep();
 932
 933         if (atomic_dec_and_test(&mm->mm_users))
 934                 __mmput(mm);
 935 }
 936 EXPORT_SYMBOL_GPL(mmput);
 937
 938 #ifdef CONFIG_MMU
 939 static void mmput_async_fn(struct work_struct *work)
 940 {
 941         struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work);
 942         __mmput(mm);
 943 }
 944
 945 void mmput_async(struct mm_struct *mm)
 946 {
 947         if (atomic_dec_and_test(&mm->mm_users)) {
 948                 INIT_WORK(&mm->async_put_work, mmput_async_fn);
 949                 schedule_work(&mm->async_put_work);
 950         }
 951 }
 952 #endif
 953
 954 /**
 955  * set_mm_exe_file - change a reference to the mm's executable file
 956  *
 957  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
 958  *
 959  * Main users are mmput() and sys_execve(). Callers prevent concurrent
 960  * invocations: in mmput() nobody alive left, in execve task is single
 961  * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
 962  * mm->exe_file, but does so without using set_mm_exe_file() in order
 963  * to do avoid the need for any locks.
 964  */
 965 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 966 {
 967         struct file *old_exe_file;
 968
 969         /*
 970          * It is safe to dereference the exe_file without RCU as
 971          * this function is only called if nobody else can access
 972          * this mm -- see comment above for justification.
 973          */
 974         old_exe_file = rcu_dereference_raw(mm->exe_file);
 975
 976         if (new_exe_file)
 977                 get_file(new_exe_file);
 978         rcu_assign_pointer(mm->exe_file, new_exe_file);
 979         if (old_exe_file)
 980                 fput(old_exe_file);
 981 }
 982
 983 /**
 984  * get_mm_exe_file - acquire a reference to the mm's executable file
 985  *
 986  * Returns %NULL if mm has no associated executable file.
 987  * User must release file via fput().
 988  */
 989 struct file *get_mm_exe_file(struct mm_struct *mm)
 990 {
 991         struct file *exe_file;
 992
 993         rcu_read_lock();
 994         exe_file = rcu_dereference(mm->exe_file);
 995         if (exe_file && !get_file_rcu(exe_file))
 996                 exe_file = NULL;
 997         rcu_read_unlock();
 998         return exe_file;
 999 }
1000 EXPORT_SYMBOL(get_mm_exe_file);
1001
1002 /**
1003  * get_task_exe_file - acquire a reference to the task's executable file
1004  *
1005  * Returns %NULL if task's mm (if any) has no associated executable file or
1006  * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1007  * User must release file via fput().
1008  */
1009 struct file *get_task_exe_file(struct task_struct *task)
1010 {
1011         struct file *exe_file = NULL;
1012         struct mm_struct *mm;
1013
1014         task_lock(task);
1015         mm = task->mm;
1016         if (mm) {
1017                 if (!(task->flags & PF_KTHREAD))
1018                         exe_file = get_mm_exe_file(mm);
1019         }
1020         task_unlock(task);
1021         return exe_file;
1022 }
1023 EXPORT_SYMBOL(get_task_exe_file);
1024
1025 /**
1026  * get_task_mm - acquire a reference to the task's mm
1027  *
1028  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
1029  * this kernel workthread has transiently adopted a user mm with use_mm,
1030  * to do its AIO) is not set and if so returns a reference to it, after
1031  * bumping up the use count.  User must release the mm via mmput()
1032  * after use.  Typically used by /proc and ptrace.
1033  */
1034 struct mm_struct *get_task_mm(struct task_struct *task)
1035 {
1036         struct mm_struct *mm;
1037
1038         task_lock(task);
1039         mm = task->mm;
1040         if (mm) {
1041                 if (task->flags & PF_KTHREAD)
1042                         mm = NULL;
1043                 else
1044                         mmget(mm);
1045         }
1046         task_unlock(task);
1047         return mm;
1048 }
1049 EXPORT_SYMBOL_GPL(get_task_mm);
1050
1051 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1052 {
1053         struct mm_struct *mm;
1054         int err;
1055
1056         err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
1057         if (err)
1058                 return ERR_PTR(err);
1059
1060         mm = get_task_mm(task);
1061         if (mm && mm != current->mm &&
1062                         !ptrace_may_access(task, mode)) {
1063                 mmput(mm);
1064                 mm = ERR_PTR(-EACCES);
1065         }
1066         mutex_unlock(&task->signal->cred_guard_mutex);
1067
1068         return mm;
1069 }
1070
1071 static void complete_vfork_done(struct task_struct *tsk)
1072 {
1073         struct completion *vfork;
1074
1075         task_lock(tsk);
1076         vfork = tsk->vfork_done;
1077         if (likely(vfork)) {
1078                 tsk->vfork_done = NULL;
1079                 complete(vfork);
1080         }
1081         task_unlock(tsk);
1082 }
1083
1084 static int wait_for_vfork_done(struct task_struct *child,
1085                                 struct completion *vfork)
1086 {
1087         int killed;
1088
1089         freezer_do_not_count();
1090         killed = wait_for_completion_killable(vfork);
1091         freezer_count();
1092
1093         if (killed) {
1094                 task_lock(child);
1095                 child->vfork_done = NULL;
1096                 task_unlock(child);
1097         }
1098
1099         put_task_struct(child);
1100         return killed;
1101 }
1102
1103 /* Please note the differences between mmput and mm_release.
1104  * mmput is called whenever we stop holding onto a mm_struct,
1105  * error success whatever.
1106  *
1107  * mm_release is called after a mm_struct has been removed
1108  * from the current process.
1109  *
1110  * This difference is important for error handling, when we
1111  * only half set up a mm_struct for a new process and need to restore
1112  * the old one.  Because we mmput the new mm_struct before
1113  * restoring the old one. . .
1114  * Eric Biederman 10 January 1998
1115  */
1116 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1117 {
1118         /* Get rid of any futexes when releasing the mm */
1119 #ifdef CONFIG_FUTEX
1120         if (unlikely(tsk->robust_list)) {
1121                 exit_robust_list(tsk);
1122                 tsk->robust_list = NULL;
1123         }
1124 #ifdef CONFIG_COMPAT
1125         if (unlikely(tsk->compat_robust_list)) {
1126                 compat_exit_robust_list(tsk);
1127                 tsk->compat_robust_list = NULL;
1128         }
1129 #endif
1130         if (unlikely(!list_empty(&tsk->pi_state_list)))
1131                 exit_pi_state_list(tsk);
1132 #endif
1133
1134         uprobe_free_utask(tsk);
1135
1136         /* Get rid of any cached register state */
1137         deactivate_mm(tsk, mm);
1138
1139         /*
1140          * Signal userspace if we're not exiting with a core dump
1141          * because we want to leave the value intact for debugging
1142          * purposes.
1143          */
1144         if (tsk->clear_child_tid) {
1145                 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1146                     atomic_read(&mm->mm_users) > 1) {
1147                         /*
1148                          * We don't check the error code - if userspace has
1149                          * not set up a proper pointer then tough luck.
1150                          */
1151                         put_user(0, tsk->clear_child_tid);
1152                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
1153                                         1, NULL, NULL, 0);
1154                 }
1155                 tsk->clear_child_tid = NULL;
1156         }
1157
1158         /*
1159          * All done, finally we can wake up parent and return this mm to him.
1160          * Also kthread_stop() uses this completion for synchronization.
1161          */
1162         if (tsk->vfork_done)
1163                 complete_vfork_done(tsk);
1164 }
1165
1166 /*
1167  * Allocate a new mm structure and copy contents from the
1168  * mm structure of the passed in task structure.
1169  */
1170 static struct mm_struct *dup_mm(struct task_struct *tsk)
1171 {
1172         struct mm_struct *mm, *oldmm = current->mm;
1173         int err;
1174
1175         mm = allocate_mm();
1176         if (!mm)
1177                 goto fail_nomem;
1178
1179         memcpy(mm, oldmm, sizeof(*mm));
1180
1181         if (!mm_init(mm, tsk, mm->user_ns))
1182                 goto fail_nomem;
1183
1184         err = dup_mmap(mm, oldmm);
1185         if (err)
1186                 goto free_pt;
1187
1188         mm->hiwater_rss = get_mm_rss(mm);
1189         mm->hiwater_vm = mm->total_vm;
1190
1191         if (mm->binfmt && !try_module_get(mm->binfmt->module))
1192                 goto free_pt;
1193
1194         return mm;
1195
1196 free_pt:
1197         /* don't put binfmt in mmput, we haven't got module yet */
1198         mm->binfmt = NULL;
1199         mmput(mm);
1200
1201 fail_nomem:
1202         return NULL;
1203 }
1204
1205 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1206 {
1207         struct mm_struct *mm, *oldmm;
1208         int retval;
1209
1210         tsk->min_flt = tsk->maj_flt = 0;
1211         tsk->nvcsw = tsk->nivcsw = 0;
1212 #ifdef CONFIG_DETECT_HUNG_TASK
1213         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1214 #endif
1215
1216         tsk->mm = NULL;
1217         tsk->active_mm = NULL;
1218
1219         /*
1220          * Are we cloning a kernel thread?
1221          *
1222          * We need to steal a active VM for that..
1223          */
1224         oldmm = current->mm;
1225         if (!oldmm)
1226                 return 0;
1227
1228         /* initialize the new vmacache entries */
1229         vmacache_flush(tsk);
1230
1231         if (clone_flags & CLONE_VM) {
1232                 mmget(oldmm);
1233                 mm = oldmm;
1234                 goto good_mm;
1235         }
1236
1237         retval = -ENOMEM;
1238         mm = dup_mm(tsk);
1239         if (!mm)
1240                 goto fail_nomem;
1241
1242 good_mm:
1243         tsk->mm = mm;
1244         tsk->active_mm = mm;
1245         return 0;
1246
1247 fail_nomem:
1248         return retval;
1249 }
1250
1251 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1252 {
1253         struct fs_struct *fs = current->fs;
1254         if (clone_flags & CLONE_FS) {
1255                 /* tsk->fs is already what we want */
1256                 spin_lock(&fs->lock);
1257                 if (fs->in_exec) {
1258                         spin_unlock(&fs->lock);
1259                         return -EAGAIN;
1260                 }
1261                 fs->users++;
1262                 spin_unlock(&fs->lock);
1263                 return 0;
1264         }
1265         tsk->fs = copy_fs_struct(fs);
1266         if (!tsk->fs)
1267                 return -ENOMEM;
1268         return 0;
1269 }
1270
1271 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1272 {
1273         struct files_struct *oldf, *newf;
1274         int error = 0;
1275
1276         /*
1277          * A background process may not have any files ...
1278          */
1279         oldf = current->files;
1280         if (!oldf)
1281                 goto out;
1282
1283         if (clone_flags & CLONE_FILES) {
1284                 atomic_inc(&oldf->count);
1285                 goto out;
1286         }
1287
1288         newf = dup_fd(oldf, &error);
1289         if (!newf)
1290                 goto out;
1291
1292         tsk->files = newf;
1293         error = 0;
1294 out:
1295         return error;
1296 }
1297
1298 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1299 {
1300 #ifdef CONFIG_BLOCK
1301         struct io_context *ioc = current->io_context;
1302         struct io_context *new_ioc;
1303
1304         if (!ioc)
1305                 return 0;
1306         /*
1307          * Share io context with parent, if CLONE_IO is set
1308          */
1309         if (clone_flags & CLONE_IO) {
1310                 ioc_task_link(ioc);
1311                 tsk->io_context = ioc;
1312         } else if (ioprio_valid(ioc->ioprio)) {
1313                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1314                 if (unlikely(!new_ioc))
1315                         return -ENOMEM;
1316
1317                 new_ioc->ioprio = ioc->ioprio;
1318                 put_io_context(new_ioc);
1319         }
1320 #endif
1321         return 0;
1322 }
1323
1324 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1325 {
1326         struct sighand_struct *sig;
1327
1328         if (clone_flags & CLONE_SIGHAND) {
1329                 atomic_inc(&current->sighand->count);
1330                 return 0;
1331         }
1332         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1333         rcu_assign_pointer(tsk->sighand, sig);
1334         if (!sig)
1335                 return -ENOMEM;
1336
1337         atomic_set(&sig->count, 1);
1338         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1339         return 0;
1340 }
1341
1342 void __cleanup_sighand(struct sighand_struct *sighand)
1343 {
1344         if (atomic_dec_and_test(&sighand->count)) {
1345                 signalfd_cleanup(sighand);
1346                 /*
1347                  * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1348                  * without an RCU grace period, see __lock_task_sighand().
1349                  */
1350                 kmem_cache_free(sighand_cachep, sighand);
1351         }
1352 }
1353
1354 #ifdef CONFIG_POSIX_TIMERS
1355 /*
1356  * Initialize POSIX timer handling for a thread group.
1357  */
1358 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1359 {
1360         unsigned long cpu_limit;
1361
1362         cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1363         if (cpu_limit != RLIM_INFINITY) {
1364                 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC;
1365                 sig->cputimer.running = true;
1366         }
1367
1368         /* The timer lists. */
1369         INIT_LIST_HEAD(&sig->cpu_timers[0]);
1370         INIT_LIST_HEAD(&sig->cpu_timers[1]);
1371         INIT_LIST_HEAD(&sig->cpu_timers[2]);
1372 }
1373 #else
1374 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { }
1375 #endif
1376
1377 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1378 {
1379         struct signal_struct *sig;
1380
1381         if (clone_flags & CLONE_THREAD)
1382                 return 0;
1383
1384         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1385         tsk->signal = sig;
1386         if (!sig)
1387                 return -ENOMEM;
1388
1389         sig->nr_threads = 1;
1390         atomic_set(&sig->live, 1);
1391         atomic_set(&sig->sigcnt, 1);
1392
1393         /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1394         sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1395         tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1396
1397         init_waitqueue_head(&sig->wait_chldexit);
1398         sig->curr_target = tsk;
1399         init_sigpending(&sig->shared_pending);
1400         seqlock_init(&sig->stats_lock);
1401         prev_cputime_init(&sig->prev_cputime);
1402
1403 #ifdef CONFIG_POSIX_TIMERS
1404         INIT_LIST_HEAD(&sig->posix_timers);
1405         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1406         sig->real_timer.function = it_real_fn;
1407 #endif
1408
1409         task_lock(current->group_leader);
1410         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1411         task_unlock(current->group_leader);
1412
1413         posix_cpu_timers_init_group(sig);
1414
1415         tty_audit_fork(sig);
1416         sched_autogroup_fork(sig);
1417
1418         sig->oom_score_adj = current->signal->oom_score_adj;
1419         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1420
1421         mutex_init(&sig->cred_guard_mutex);
1422
1423         return 0;
1424 }
1425
1426 static void copy_seccomp(struct task_struct *p)
1427 {
1428 #ifdef CONFIG_SECCOMP
1429         /*
1430          * Must be called with sighand->lock held, which is common to
1431          * all threads in the group. Holding cred_guard_mutex is not
1432          * needed because this new task is not yet running and cannot
1433          * be racing exec.
1434          */
1435         assert_spin_locked(&current->sighand->siglock);
1436
1437         /* Ref-count the new filter user, and assign it. */
1438         get_seccomp_filter(current);
1439         p->seccomp = current->seccomp;
1440
1441         /*
1442          * Explicitly enable no_new_privs here in case it got set
1443          * between the task_struct being duplicated and holding the
1444          * sighand lock. The seccomp state and nnp must be in sync.
1445          */
1446         if (task_no_new_privs(current))
1447                 task_set_no_new_privs(p);
1448
1449         /*
1450          * If the parent gained a seccomp mode after copying thread
1451          * flags and between before we held the sighand lock, we have
1452          * to manually enable the seccomp thread flag here.
1453          */
1454         if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1455                 set_tsk_thread_flag(p, TIF_SECCOMP);
1456 #endif
1457 }
1458
1459 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1460 {
1461         current->clear_child_tid = tidptr;
1462
1463         return task_pid_vnr(current);
1464 }
1465
1466 static void rt_mutex_init_task(struct task_struct *p)
1467 {
1468         raw_spin_lock_init(&p->pi_lock);
1469 #ifdef CONFIG_RT_MUTEXES
1470         p->pi_waiters = RB_ROOT;
1471         p->pi_waiters_leftmost = NULL;
1472         p->pi_top_task = NULL;
1473         p->pi_blocked_on = NULL;
1474 #endif
1475 }
1476
1477 #ifdef CONFIG_POSIX_TIMERS
1478 /*
1479  * Initialize POSIX timer handling for a single task.
1480  */
1481 static void posix_cpu_timers_init(struct task_struct *tsk)
1482 {
1483         tsk->cputime_expires.prof_exp = 0;
1484         tsk->cputime_expires.virt_exp = 0;
1485         tsk->cputime_expires.sched_exp = 0;
1486         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1487         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1488         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1489 }
1490 #else
1491 static inline void posix_cpu_timers_init(struct task_struct *tsk) { }
1492 #endif
1493
1494 static inline void
1495 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1496 {
1497          task->pids[type].pid = pid;
1498 }
1499
1500 static inline void rcu_copy_process(struct task_struct *p)
1501 {
1502 #ifdef CONFIG_PREEMPT_RCU
1503         p->rcu_read_lock_nesting = 0;
1504         p->rcu_read_unlock_special.s = 0;
1505         p->rcu_blocked_node = NULL;
1506         INIT_LIST_HEAD(&p->rcu_node_entry);
1507 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1508 #ifdef CONFIG_TASKS_RCU
1509         p->rcu_tasks_holdout = false;
1510         INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1511         p->rcu_tasks_idle_cpu = -1;
1512 #endif /* #ifdef CONFIG_TASKS_RCU */
1513 }
1514
1515 /*
1516  * This creates a new process as a copy of the old one,
1517  * but does not actually start it yet.
1518  *
1519  * It copies the registers, and all the appropriate
1520  * parts of the process environment (as per the clone
1521  * flags). The actual kick-off is left to the caller.
1522  */
1523 static __latent_entropy struct task_struct *copy_process(
1524                                         unsigned long clone_flags,
1525                                         unsigned long stack_start,
1526                                         unsigned long stack_size,
1527                                         int __user *child_tidptr,
1528                                         struct pid *pid,
1529                                         int trace,
1530                                         unsigned long tls,
1531                                         int node)
1532 {
1533         int retval;
1534         struct task_struct *p;
1535
1536         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1537                 return ERR_PTR(-EINVAL);
1538
1539         if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1540                 return ERR_PTR(-EINVAL);
1541
1542         /*
1543          * Thread groups must share signals as well, and detached threads
1544          * can only be started up within the thread group.
1545          */
1546         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1547                 return ERR_PTR(-EINVAL);
1548
1549         /*
1550          * Shared signal handlers imply shared VM. By way of the above,
1551          * thread groups also imply shared VM. Blocking this case allows
1552          * for various simplifications in other code.
1553          */
1554         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1555                 return ERR_PTR(-EINVAL);
1556
1557         /*
1558          * Siblings of global init remain as zombies on exit since they are
1559          * not reaped by their parent (swapper). To solve this and to avoid
1560          * multi-rooted process trees, prevent global and container-inits
1561          * from creating siblings.
1562          */
1563         if ((clone_flags & CLONE_PARENT) &&
1564                                 current->signal->flags & SIGNAL_UNKILLABLE)
1565                 return ERR_PTR(-EINVAL);
1566
1567         /*
1568          * If the new process will be in a different pid or user namespace
1569          * do not allow it to share a thread group with the forking task.
1570          */
1571         if (clone_flags & CLONE_THREAD) {
1572                 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1573                     (task_active_pid_ns(current) !=
1574                                 current->nsproxy->pid_ns_for_children))
1575                         return ERR_PTR(-EINVAL);
1576         }
1577
1578         retval = security_task_create(clone_flags);
1579         if (retval)
1580                 goto fork_out;
1581
1582         retval = -ENOMEM;
1583         p = dup_task_struct(current, node);
1584         if (!p)
1585                 goto fork_out;
1586
1587         /*
1588          * This _must_ happen before we call free_task(), i.e. before we jump
1589          * to any of the bad_fork_* labels. This is to avoid freeing
1590          * p->set_child_tid which is (ab)used as a kthread's data pointer for
1591          * kernel threads (PF_KTHREAD).
1592          */
1593         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1594         /*
1595          * Clear TID on mm_release()?
1596          */
1597         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1598
1599         ftrace_graph_init_task(p);
1600
1601         rt_mutex_init_task(p);
1602
1603 #ifdef CONFIG_PROVE_LOCKING
1604         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1605         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1606 #endif
1607         retval = -EAGAIN;
1608         if (atomic_read(&p->real_cred->user->processes) >=
1609                         task_rlimit(p, RLIMIT_NPROC)) {
1610                 if (p->real_cred->user != INIT_USER &&
1611                     !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1612                         goto bad_fork_free;
1613         }
1614         current->flags &= ~PF_NPROC_EXCEEDED;
1615
1616         retval = copy_creds(p, clone_flags);
1617         if (retval < 0)
1618                 goto bad_fork_free;
1619
1620         /*
1621          * If multiple threads are within copy_process(), then this check
1622          * triggers too late. This doesn't hurt, the check is only there
1623          * to stop root fork bombs.
1624          */
1625         retval = -EAGAIN;
1626         if (nr_threads >= max_threads)
1627                 goto bad_fork_cleanup_count;
1628
1629         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1630         p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1631         p->flags |= PF_FORKNOEXEC;
1632         INIT_LIST_HEAD(&p->children);
1633         INIT_LIST_HEAD(&p->sibling);
1634         rcu_copy_process(p);
1635         p->vfork_done = NULL;
1636         spin_lock_init(&p->alloc_lock);
1637
1638         init_sigpending(&p->pending);
1639
1640         p->utime = p->stime = p->gtime = 0;
1641 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1642         p->utimescaled = p->stimescaled = 0;
1643 #endif
1644         prev_cputime_init(&p->prev_cputime);
1645
1646 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1647         seqcount_init(&p->vtime.seqcount);
1648         p->vtime.starttime = 0;
1649         p->vtime.state = VTIME_INACTIVE;
1650 #endif
1651
1652 #if defined(SPLIT_RSS_COUNTING)
1653         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1654 #endif
1655
1656         p->default_timer_slack_ns = current->timer_slack_ns;
1657
1658         task_io_accounting_init(&p->ioac);
1659         acct_clear_integrals(p);
1660
1661         posix_cpu_timers_init(p);
1662
1663         p->start_time = ktime_get_ns();
1664         p->real_start_time = ktime_get_boot_ns();
1665         p->io_context = NULL;
1666         p->audit_context = NULL;
1667         cgroup_fork(p);
1668 #ifdef CONFIG_NUMA
1669         p->mempolicy = mpol_dup(p->mempolicy);
1670         if (IS_ERR(p->mempolicy)) {
1671                 retval = PTR_ERR(p->mempolicy);
1672                 p->mempolicy = NULL;
1673                 goto bad_fork_cleanup_threadgroup_lock;
1674         }
1675 #endif
1676 #ifdef CONFIG_CPUSETS
1677         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1678         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1679         seqcount_init(&p->mems_allowed_seq);
1680 #endif
1681 #ifdef CONFIG_TRACE_IRQFLAGS
1682         p->irq_events = 0;
1683         p->hardirqs_enabled = 0;
1684         p->hardirq_enable_ip = 0;
1685         p->hardirq_enable_event = 0;
1686         p->hardirq_disable_ip = _THIS_IP_;
1687         p->hardirq_disable_event = 0;
1688         p->softirqs_enabled = 1;
1689         p->softirq_enable_ip = _THIS_IP_;
1690         p->softirq_enable_event = 0;
1691         p->softirq_disable_ip = 0;
1692         p->softirq_disable_event = 0;
1693         p->hardirq_context = 0;
1694         p->softirq_context = 0;
1695 #endif
1696
1697         p->pagefault_disabled = 0;
1698
1699 #ifdef CONFIG_LOCKDEP
1700         p->lockdep_depth = 0; /* no locks held yet */
1701         p->curr_chain_key = 0;
1702         p->lockdep_recursion = 0;
1703 #endif
1704
1705 #ifdef CONFIG_DEBUG_MUTEXES
1706         p->blocked_on = NULL; /* not blocked yet */
1707 #endif
1708 #ifdef CONFIG_BCACHE
1709         p->sequential_io        = 0;
1710         p->sequential_io_avg    = 0;
1711 #endif
1712
1713         /* Perform scheduler related setup. Assign this task to a CPU. */
1714         retval = sched_fork(clone_flags, p);
1715         if (retval)
1716                 goto bad_fork_cleanup_policy;
1717
1718         retval = perf_event_init_task(p);
1719         if (retval)
1720                 goto bad_fork_cleanup_policy;
1721         retval = audit_alloc(p);
1722         if (retval)
1723                 goto bad_fork_cleanup_perf;
1724         /* copy all the process information */
1725         shm_init_task(p);
1726         retval = security_task_alloc(p, clone_flags);
1727         if (retval)
1728                 goto bad_fork_cleanup_audit;
1729         retval = copy_semundo(clone_flags, p);
1730         if (retval)
1731                 goto bad_fork_cleanup_security;
1732         retval = copy_files(clone_flags, p);
1733         if (retval)
1734                 goto bad_fork_cleanup_semundo;
1735         retval = copy_fs(clone_flags, p);
1736         if (retval)
1737                 goto bad_fork_cleanup_files;
1738         retval = copy_sighand(clone_flags, p);
1739         if (retval)
1740                 goto bad_fork_cleanup_fs;
1741         retval = copy_signal(clone_flags, p);
1742         if (retval)
1743                 goto bad_fork_cleanup_sighand;
1744         retval = copy_mm(clone_flags, p);
1745         if (retval)
1746                 goto bad_fork_cleanup_signal;
1747         retval = copy_namespaces(clone_flags, p);
1748         if (retval)
1749                 goto bad_fork_cleanup_mm;
1750         retval = copy_io(clone_flags, p);
1751         if (retval)
1752                 goto bad_fork_cleanup_namespaces;
1753         retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1754         if (retval)
1755                 goto bad_fork_cleanup_io;
1756
1757         if (pid != &init_struct_pid) {
1758                 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1759                 if (IS_ERR(pid)) {
1760                         retval = PTR_ERR(pid);
1761                         goto bad_fork_cleanup_thread;
1762                 }
1763         }
1764
1765 #ifdef CONFIG_BLOCK
1766         p->plug = NULL;
1767 #endif
1768 #ifdef CONFIG_FUTEX
1769         p->robust_list = NULL;
1770 #ifdef CONFIG_COMPAT
1771         p->compat_robust_list = NULL;
1772 #endif
1773         INIT_LIST_HEAD(&p->pi_state_list);
1774         p->pi_state_cache = NULL;
1775 #endif
1776         /*
1777          * sigaltstack should be cleared when sharing the same VM
1778          */
1779         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1780                 sas_ss_reset(p);
1781
1782         /*
1783          * Syscall tracing and stepping should be turned off in the
1784          * child regardless of CLONE_PTRACE.
1785          */
1786         user_disable_single_step(p);
1787         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1788 #ifdef TIF_SYSCALL_EMU
1789         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1790 #endif
1791         clear_all_latency_tracing(p);
1792
1793         /* ok, now we should be set up.. */
1794         p->pid = pid_nr(pid);
1795         if (clone_flags & CLONE_THREAD) {
1796                 p->exit_signal = -1;
1797                 p->group_leader = current->group_leader;
1798                 p->tgid = current->tgid;
1799         } else {
1800                 if (clone_flags & CLONE_PARENT)
1801                         p->exit_signal = current->group_leader->exit_signal;
1802                 else
1803                         p->exit_signal = (clone_flags & CSIGNAL);
1804                 p->group_leader = p;
1805                 p->tgid = p->pid;
1806         }
1807
1808         p->nr_dirtied = 0;
1809         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1810         p->dirty_paused_when = 0;
1811
1812         p->pdeath_signal = 0;
1813         INIT_LIST_HEAD(&p->thread_group);
1814         p->task_works = NULL;
1815
1816         cgroup_threadgroup_change_begin(current);
1817         /*
1818          * Ensure that the cgroup subsystem policies allow the new process to be
1819          * forked. It should be noted the the new process's css_set can be changed
1820          * between here and cgroup_post_fork() if an organisation operation is in
1821          * progress.
1822          */
1823         retval = cgroup_can_fork(p);
1824         if (retval)
1825                 goto bad_fork_free_pid;
1826
1827         /*
1828          * Make it visible to the rest of the system, but dont wake it up yet.
1829          * Need tasklist lock for parent etc handling!
1830          */
1831         write_lock_irq(&tasklist_lock);
1832
1833         /* CLONE_PARENT re-uses the old parent */
1834         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1835                 p->real_parent = current->real_parent;
1836                 p->parent_exec_id = current->parent_exec_id;
1837         } else {
1838                 p->real_parent = current;
1839                 p->parent_exec_id = current->self_exec_id;
1840         }
1841
1842         klp_copy_process(p);
1843
1844         spin_lock(&current->sighand->siglock);
1845
1846         /*
1847          * Copy seccomp details explicitly here, in case they were changed
1848          * before holding sighand lock.
1849          */
1850         copy_seccomp(p);
1851
1852         /*
1853          * Process group and session signals need to be delivered to just the
1854          * parent before the fork or both the parent and the child after the
1855          * fork. Restart if a signal comes in before we add the new process to
1856          * it's process group.
1857          * A fatal signal pending means that current will exit, so the new
1858          * thread can't slip out of an OOM kill (or normal SIGKILL).
1859         */
1860         recalc_sigpending();
1861         if (signal_pending(current)) {
1862                 retval = -ERESTARTNOINTR;
1863                 goto bad_fork_cancel_cgroup;
1864         }
1865         if (unlikely(!(ns_of_pid(pid)->nr_hashed & PIDNS_HASH_ADDING))) {
1866                 retval = -ENOMEM;
1867                 goto bad_fork_cancel_cgroup;
1868         }
1869
1870         if (likely(p->pid)) {
1871                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1872
1873                 init_task_pid(p, PIDTYPE_PID, pid);
1874                 if (thread_group_leader(p)) {
1875                         init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1876                         init_task_pid(p, PIDTYPE_SID, task_session(current));
1877
1878                         if (is_child_reaper(pid)) {
1879                                 ns_of_pid(pid)->child_reaper = p;
1880                                 p->signal->flags |= SIGNAL_UNKILLABLE;
1881                         }
1882
1883                         p->signal->leader_pid = pid;
1884                         p->signal->tty = tty_kref_get(current->signal->tty);
1885                         /*
1886                          * Inherit has_child_subreaper flag under the same
1887                          * tasklist_lock with adding child to the process tree
1888                          * for propagate_has_child_subreaper optimization.
1889                          */
1890                         p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
1891                                                          p->real_parent->signal->is_child_subreaper;
1892                         list_add_tail(&p->sibling, &p->real_parent->children);
1893                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1894                         attach_pid(p, PIDTYPE_PGID);
1895                         attach_pid(p, PIDTYPE_SID);
1896                         __this_cpu_inc(process_counts);
1897                 } else {
1898                         current->signal->nr_threads++;
1899                         atomic_inc(&current->signal->live);
1900                         atomic_inc(&current->signal->sigcnt);
1901                         list_add_tail_rcu(&p->thread_group,
1902                                           &p->group_leader->thread_group);
1903                         list_add_tail_rcu(&p->thread_node,
1904                                           &p->signal->thread_head);
1905                 }
1906                 attach_pid(p, PIDTYPE_PID);
1907                 nr_threads++;
1908         }
1909
1910         total_forks++;
1911         spin_unlock(&current->sighand->siglock);
1912         syscall_tracepoint_update(p);
1913         write_unlock_irq(&tasklist_lock);
1914
1915         proc_fork_connector(p);
1916         cgroup_post_fork(p);
1917         cgroup_threadgroup_change_end(current);
1918         perf_event_fork(p);
1919
1920         trace_task_newtask(p, clone_flags);
1921         uprobe_copy_process(p, clone_flags);
1922
1923         return p;
1924
1925 bad_fork_cancel_cgroup:
1926         spin_unlock(&current->sighand->siglock);
1927         write_unlock_irq(&tasklist_lock);
1928         cgroup_cancel_fork(p);
1929 bad_fork_free_pid:
1930         cgroup_threadgroup_change_end(current);
1931         if (pid != &init_struct_pid)
1932                 free_pid(pid);
1933 bad_fork_cleanup_thread:
1934         exit_thread(p);
1935 bad_fork_cleanup_io:
1936         if (p->io_context)
1937                 exit_io_context(p);
1938 bad_fork_cleanup_namespaces:
1939         exit_task_namespaces(p);
1940 bad_fork_cleanup_mm:
1941         if (p->mm)
1942                 mmput(p->mm);
1943 bad_fork_cleanup_signal:
1944         if (!(clone_flags & CLONE_THREAD))
1945                 free_signal_struct(p->signal);
1946 bad_fork_cleanup_sighand:
1947         __cleanup_sighand(p->sighand);
1948 bad_fork_cleanup_fs:
1949         exit_fs(p); /* blocking */
1950 bad_fork_cleanup_files:
1951         exit_files(p); /* blocking */
1952 bad_fork_cleanup_semundo:
1953         exit_sem(p);
1954 bad_fork_cleanup_security:
1955         security_task_free(p);
1956 bad_fork_cleanup_audit:
1957         audit_free(p);
1958 bad_fork_cleanup_perf:
1959         perf_event_free_task(p);
1960 bad_fork_cleanup_policy:
1961 #ifdef CONFIG_NUMA
1962         mpol_put(p->mempolicy);
1963 bad_fork_cleanup_threadgroup_lock:
1964 #endif
1965         delayacct_tsk_free(p);
1966 bad_fork_cleanup_count:
1967         atomic_dec(&p->cred->user->processes);
1968         exit_creds(p);
1969 bad_fork_free:
1970         p->state = TASK_DEAD;
1971         put_task_stack(p);
1972         free_task(p);
1973 fork_out:
1974         return ERR_PTR(retval);
1975 }
1976
1977 static inline void init_idle_pids(struct pid_link *links)
1978 {
1979         enum pid_type type;
1980
1981         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1982                 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1983                 links[type].pid = &init_struct_pid;
1984         }
1985 }
1986
1987 struct task_struct *fork_idle(int cpu)
1988 {
1989         struct task_struct *task;
1990         task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
1991                             cpu_to_node(cpu));
1992         if (!IS_ERR(task)) {
1993                 init_idle_pids(task->pids);
1994                 init_idle(task, cpu);
1995         }
1996
1997         return task;
1998 }
1999
2000 /*
2001  *  Ok, this is the main fork-routine.
2002  *
2003  * It copies the process, and if successful kick-starts
2004  * it and waits for it to finish using the VM if required.
2005  */
2006 long _do_fork(unsigned long clone_flags,
2007               unsigned long stack_start,
2008               unsigned long stack_size,
2009               int __user *parent_tidptr,
2010               int __user *child_tidptr,
2011               unsigned long tls)
2012 {
2013         struct task_struct *p;
2014         int trace = 0;
2015         long nr;
2016
2017         /*
2018          * Determine whether and which event to report to ptracer.  When
2019          * called from kernel_thread or CLONE_UNTRACED is explicitly
2020          * requested, no event is reported; otherwise, report if the event
2021          * for the type of forking is enabled.
2022          */
2023         if (!(clone_flags & CLONE_UNTRACED)) {
2024                 if (clone_flags & CLONE_VFORK)
2025                         trace = PTRACE_EVENT_VFORK;
2026                 else if ((clone_flags & CSIGNAL) != SIGCHLD)
2027                         trace = PTRACE_EVENT_CLONE;
2028                 else
2029                         trace = PTRACE_EVENT_FORK;
2030
2031                 if (likely(!ptrace_event_enabled(current, trace)))
2032                         trace = 0;
2033         }
2034
2035         p = copy_process(clone_flags, stack_start, stack_size,
2036                          child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
2037         add_latent_entropy();
2038         /*
2039          * Do this prior waking up the new thread - the thread pointer
2040          * might get invalid after that point, if the thread exits quickly.
2041          */
2042         if (!IS_ERR(p)) {
2043                 struct completion vfork;
2044                 struct pid *pid;
2045
2046                 trace_sched_process_fork(current, p);
2047
2048                 pid = get_task_pid(p, PIDTYPE_PID);
2049                 nr = pid_vnr(pid);
2050
2051                 if (clone_flags & CLONE_PARENT_SETTID)
2052                         put_user(nr, parent_tidptr);
2053
2054                 if (clone_flags & CLONE_VFORK) {
2055                         p->vfork_done = &vfork;
2056                         init_completion(&vfork);
2057                         get_task_struct(p);
2058                 }
2059
2060                 wake_up_new_task(p);
2061
2062                 /* forking complete and child started to run, tell ptracer */
2063                 if (unlikely(trace))
2064                         ptrace_event_pid(trace, pid);
2065
2066                 if (clone_flags & CLONE_VFORK) {
2067                         if (!wait_for_vfork_done(p, &vfork))
2068                                 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2069                 }
2070
2071                 put_pid(pid);
2072         } else {
2073                 nr = PTR_ERR(p);
2074         }
2075         return nr;
2076 }
2077
2078 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
2079 /* For compatibility with architectures that call do_fork directly rather than
2080  * using the syscall entry points below. */
2081 long do_fork(unsigned long clone_flags,
2082               unsigned long stack_start,
2083               unsigned long stack_size,
2084               int __user *parent_tidptr,
2085               int __user *child_tidptr)
2086 {
2087         return _do_fork(clone_flags, stack_start, stack_size,
2088                         parent_tidptr, child_tidptr, 0);
2089 }
2090 #endif
2091
2092 /*
2093  * Create a kernel thread.
2094  */
2095 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2096 {
2097         return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
2098                 (unsigned long)arg, NULL, NULL, 0);
2099 }
2100
2101 #ifdef __ARCH_WANT_SYS_FORK
2102 SYSCALL_DEFINE0(fork)
2103 {
2104 #ifdef CONFIG_MMU
2105         return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
2106 #else
2107         /* can not support in nommu mode */
2108         return -EINVAL;
2109 #endif
2110 }
2111 #endif
2112
2113 #ifdef __ARCH_WANT_SYS_VFORK
2114 SYSCALL_DEFINE0(vfork)
2115 {
2116         return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
2117                         0, NULL, NULL, 0);
2118 }
2119 #endif
2120
2121 #ifdef __ARCH_WANT_SYS_CLONE
2122 #ifdef CONFIG_CLONE_BACKWARDS
2123 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2124                  int __user *, parent_tidptr,
2125                  unsigned long, tls,
2126                  int __user *, child_tidptr)
2127 #elif defined(CONFIG_CLONE_BACKWARDS2)
2128 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2129                  int __user *, parent_tidptr,
2130                  int __user *, child_tidptr,
2131                  unsigned long, tls)
2132 #elif defined(CONFIG_CLONE_BACKWARDS3)
2133 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2134                 int, stack_size,
2135                 int __user *, parent_tidptr,
2136                 int __user *, child_tidptr,
2137                 unsigned long, tls)
2138 #else
2139 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2140                  int __user *, parent_tidptr,
2141                  int __user *, child_tidptr,
2142                  unsigned long, tls)
2143 #endif
2144 {
2145         return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
2146 }
2147 #endif
2148
2149 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2150 {
2151         struct task_struct *leader, *parent, *child;
2152         int res;
2153
2154         read_lock(&tasklist_lock);
2155         leader = top = top->group_leader;
2156 down:
2157         for_each_thread(leader, parent) {
2158                 list_for_each_entry(child, &parent->children, sibling) {
2159                         res = visitor(child, data);
2160                         if (res) {
2161                                 if (res < 0)
2162                                         goto out;
2163                                 leader = child;
2164                                 goto down;
2165                         }
2166 up:
2167                         ;
2168                 }
2169         }
2170
2171         if (leader != top) {
2172                 child = leader;
2173                 parent = child->real_parent;
2174                 leader = parent->group_leader;
2175                 goto up;
2176         }
2177 out:
2178         read_unlock(&tasklist_lock);
2179 }
2180
2181 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2182 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2183 #endif
2184
2185 static void sighand_ctor(void *data)
2186 {
2187         struct sighand_struct *sighand = data;
2188
2189         spin_lock_init(&sighand->siglock);
2190         init_waitqueue_head(&sighand->signalfd_wqh);
2191 }
2192
2193 void __init proc_caches_init(void)
2194 {
2195         sighand_cachep = kmem_cache_create("sighand_cache",
2196                         sizeof(struct sighand_struct), 0,
2197                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2198                         SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor);
2199         signal_cachep = kmem_cache_create("signal_cache",
2200                         sizeof(struct signal_struct), 0,
2201                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2202                         NULL);
2203         files_cachep = kmem_cache_create("files_cache",
2204                         sizeof(struct files_struct), 0,
2205                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2206                         NULL);
2207         fs_cachep = kmem_cache_create("fs_cache",
2208                         sizeof(struct fs_struct), 0,
2209                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2210                         NULL);
2211         /*
2212          * FIXME! The "sizeof(struct mm_struct)" currently includes the
2213          * whole struct cpumask for the OFFSTACK case. We could change
2214          * this to *only* allocate as much of it as required by the
2215          * maximum number of CPU's we can ever have.  The cpumask_allocation
2216          * is at the end of the structure, exactly for that reason.
2217          */
2218         mm_cachep = kmem_cache_create("mm_struct",
2219                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
2220                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2221                         NULL);
2222         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2223         mmap_init();
2224         nsproxy_cache_init();
2225 }
2226
2227 /*
2228  * Check constraints on flags passed to the unshare system call.
2229  */
2230 static int check_unshare_flags(unsigned long unshare_flags)
2231 {
2232         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2233                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2234                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2235                                 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2236                 return -EINVAL;
2237         /*
2238          * Not implemented, but pretend it works if there is nothing
2239          * to unshare.  Note that unsharing the address space or the
2240          * signal handlers also need to unshare the signal queues (aka
2241          * CLONE_THREAD).
2242          */
2243         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2244                 if (!thread_group_empty(current))
2245                         return -EINVAL;
2246         }
2247         if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2248                 if (atomic_read(&current->sighand->count) > 1)
2249                         return -EINVAL;
2250         }
2251         if (unshare_flags & CLONE_VM) {
2252                 if (!current_is_single_threaded())
2253                         return -EINVAL;
2254         }
2255
2256         return 0;
2257 }
2258
2259 /*
2260  * Unshare the filesystem structure if it is being shared
2261  */
2262 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2263 {
2264         struct fs_struct *fs = current->fs;
2265
2266         if (!(unshare_flags & CLONE_FS) || !fs)
2267                 return 0;
2268
2269         /* don't need lock here; in the worst case we'll do useless copy */
2270         if (fs->users == 1)
2271                 return 0;
2272
2273         *new_fsp = copy_fs_struct(fs);
2274         if (!*new_fsp)
2275                 return -ENOMEM;
2276
2277         return 0;
2278 }
2279
2280 /*
2281  * Unshare file descriptor table if it is being shared
2282  */
2283 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2284 {
2285         struct files_struct *fd = current->files;
2286         int error = 0;
2287
2288         if ((unshare_flags & CLONE_FILES) &&
2289             (fd && atomic_read(&fd->count) > 1)) {
2290                 *new_fdp = dup_fd(fd, &error);
2291                 if (!*new_fdp)
2292                         return error;
2293         }
2294
2295         return 0;
2296 }
2297
2298 /*
2299  * unshare allows a process to 'unshare' part of the process
2300  * context which was originally shared using clone.  copy_*
2301  * functions used by do_fork() cannot be used here directly
2302  * because they modify an inactive task_struct that is being
2303  * constructed. Here we are modifying the current, active,
2304  * task_struct.
2305  */
2306 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2307 {
2308         struct fs_struct *fs, *new_fs = NULL;
2309         struct files_struct *fd, *new_fd = NULL;
2310         struct cred *new_cred = NULL;
2311         struct nsproxy *new_nsproxy = NULL;
2312         int do_sysvsem = 0;
2313         int err;
2314
2315         /*
2316          * If unsharing a user namespace must also unshare the thread group
2317          * and unshare the filesystem root and working directories.
2318          */
2319         if (unshare_flags & CLONE_NEWUSER)
2320                 unshare_flags |= CLONE_THREAD | CLONE_FS;
2321         /*
2322          * If unsharing vm, must also unshare signal handlers.
2323          */
2324         if (unshare_flags & CLONE_VM)
2325                 unshare_flags |= CLONE_SIGHAND;
2326         /*
2327          * If unsharing a signal handlers, must also unshare the signal queues.
2328          */
2329         if (unshare_flags & CLONE_SIGHAND)
2330                 unshare_flags |= CLONE_THREAD;
2331         /*
2332          * If unsharing namespace, must also unshare filesystem information.
2333          */
2334         if (unshare_flags & CLONE_NEWNS)
2335                 unshare_flags |= CLONE_FS;
2336
2337         err = check_unshare_flags(unshare_flags);
2338         if (err)
2339                 goto bad_unshare_out;
2340         /*
2341          * CLONE_NEWIPC must also detach from the undolist: after switching
2342          * to a new ipc namespace, the semaphore arrays from the old
2343          * namespace are unreachable.
2344          */
2345         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2346                 do_sysvsem = 1;
2347         err = unshare_fs(unshare_flags, &new_fs);
2348         if (err)
2349                 goto bad_unshare_out;
2350         err = unshare_fd(unshare_flags, &new_fd);
2351         if (err)
2352                 goto bad_unshare_cleanup_fs;
2353         err = unshare_userns(unshare_flags, &new_cred);
2354         if (err)
2355                 goto bad_unshare_cleanup_fd;
2356         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2357                                          new_cred, new_fs);
2358         if (err)
2359                 goto bad_unshare_cleanup_cred;
2360
2361         if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2362                 if (do_sysvsem) {
2363                         /*
2364                          * CLONE_SYSVSEM is equivalent to sys_exit().
2365                          */
2366                         exit_sem(current);
2367                 }
2368                 if (unshare_flags & CLONE_NEWIPC) {
2369                         /* Orphan segments in old ns (see sem above). */
2370                         exit_shm(current);
2371                         shm_init_task(current);
2372                 }
2373
2374                 if (new_nsproxy)
2375                         switch_task_namespaces(current, new_nsproxy);
2376
2377                 task_lock(current);
2378
2379                 if (new_fs) {
2380                         fs = current->fs;
2381                         spin_lock(&fs->lock);
2382                         current->fs = new_fs;
2383                         if (--fs->users)
2384                                 new_fs = NULL;
2385                         else
2386                                 new_fs = fs;
2387                         spin_unlock(&fs->lock);
2388                 }
2389
2390                 if (new_fd) {
2391                         fd = current->files;
2392                         current->files = new_fd;
2393                         new_fd = fd;
2394                 }
2395
2396                 task_unlock(current);
2397
2398                 if (new_cred) {
2399                         /* Install the new user namespace */
2400                         commit_creds(new_cred);
2401                         new_cred = NULL;
2402                 }
2403         }
2404
2405         perf_event_namespaces(current);
2406
2407 bad_unshare_cleanup_cred:
2408         if (new_cred)
2409                 put_cred(new_cred);
2410 bad_unshare_cleanup_fd:
2411         if (new_fd)
2412                 put_files_struct(new_fd);
2413
2414 bad_unshare_cleanup_fs:
2415         if (new_fs)
2416                 free_fs_struct(new_fs);
2417
2418 bad_unshare_out:
2419         return err;
2420 }
2421
2422 /*
2423  *      Helper to unshare the files of the current task.
2424  *      We don't want to expose copy_files internals to
2425  *      the exec layer of the kernel.
2426  */
2427
2428 int unshare_files(struct files_struct **displaced)
2429 {
2430         struct task_struct *task = current;
2431         struct files_struct *copy = NULL;
2432         int error;
2433
2434         error = unshare_fd(CLONE_FILES, &copy);
2435         if (error || !copy) {
2436                 *displaced = NULL;
2437                 return error;
2438         }
2439         *displaced = task->files;
2440         task_lock(task);
2441         task->files = copy;
2442         task_unlock(task);
2443         return 0;
2444 }
2445
2446 int sysctl_max_threads(struct ctl_table *table, int write,
2447                        void __user *buffer, size_t *lenp, loff_t *ppos)
2448 {
2449         struct ctl_table t;
2450         int ret;
2451         int threads = max_threads;
2452         int min = MIN_THREADS;
2453         int max = MAX_THREADS;
2454
2455         t = *table;
2456         t.data = &threads;
2457         t.extra1 = &min;
2458         t.extra2 = &max;
2459
2460         ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2461         if (ret || !write)
2462                 return ret;
2463
2464         set_max_threads(threads);
2465
2466         return 0;
2467 }