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