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