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