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->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                        vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 387                                                        -vma_pages(mpnt));
 388                        continue;
 389                }
 390                charge = 0;
 391                if (mpnt->vm_flags & VM_ACCOUNT) {
 392                        unsigned long len = vma_pages(mpnt);
 393
 394                        if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
 395                                goto fail_nomem;
 396                        charge = len;
 397                }
 398                tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 399                if (!tmp)
 400                        goto fail_nomem;
 401                *tmp = *mpnt;
 402                INIT_LIST_HEAD(&tmp->anon_vma_chain);
 403                pol = mpol_dup(vma_policy(mpnt));
 404                retval = PTR_ERR(pol);
 405                if (IS_ERR(pol))
 406                        goto fail_nomem_policy;
 407                vma_set_policy(tmp, pol);
 408                tmp->vm_mm = mm;
 409                if (anon_vma_fork(tmp, mpnt))
 410                        goto fail_nomem_anon_vma_fork;
 411                tmp->vm_flags &= ~VM_LOCKED;
 412                tmp->vm_next = tmp->vm_prev = NULL;
 413                file = tmp->vm_file;
 414                if (file) {
 415                        struct inode *inode = file_inode(file);
 416                        struct address_space *mapping = file->f_mapping;
 417
 418                        get_file(file);
 419                        if (tmp->vm_flags & VM_DENYWRITE)
 420                                atomic_dec(&inode->i_writecount);
 421                        mutex_lock(&mapping->i_mmap_mutex);
 422                        if (tmp->vm_flags & VM_SHARED)
 423                                mapping->i_mmap_writable++;
 424                        flush_dcache_mmap_lock(mapping);
 425                        /* insert tmp into the share list, just after mpnt */
 426                        if (unlikely(tmp->vm_flags & VM_NONLINEAR))
 427                                vma_nonlinear_insert(tmp,
 428                                                &mapping->i_mmap_nonlinear);
 429                        else
 430                                vma_interval_tree_insert_after(tmp, mpnt,
 431                                                        &mapping->i_mmap);
 432                        flush_dcache_mmap_unlock(mapping);
 433                        mutex_unlock(&mapping->i_mmap_mutex);
 434                }
 435
 436                /*
 437                 * Clear hugetlb-related page reserves for children. This only
 438                 * affects MAP_PRIVATE mappings. Faults generated by the child
 439                 * are not guaranteed to succeed, even if read-only
 440                 */
 441                if (is_vm_hugetlb_page(tmp))
 442                        reset_vma_resv_huge_pages(tmp);
 443
 444                /*
 445                 * Link in the new vma and copy the page table entries.
 446                 */
 447                *pprev = tmp;
 448                pprev = &tmp->vm_next;
 449                tmp->vm_prev = prev;
 450                prev = tmp;
 451
 452                __vma_link_rb(mm, tmp, rb_link, rb_parent);
 453                rb_link = &tmp->vm_rb.rb_right;
 454                rb_parent = &tmp->vm_rb;
 455
 456                mm->map_count++;
 457                retval = copy_page_range(mm, oldmm, mpnt);
 458
 459                if (tmp->vm_ops && tmp->vm_ops->open)
 460                        tmp->vm_ops->open(tmp);
 461
 462                if (retval)
 463                        goto out;
 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        uprobe_end_dup_mmap();
 473        return retval;
 474fail_nomem_anon_vma_fork:
 475        mpol_put(pol);
 476fail_nomem_policy:
 477        kmem_cache_free(vm_area_cachep, tmp);
 478fail_nomem:
 479        retval = -ENOMEM;
 480        vm_unacct_memory(charge);
 481        goto out;
 482}
 483
 484static inline int mm_alloc_pgd(struct mm_struct *mm)
 485{
 486        mm->pgd = pgd_alloc(mm);
 487        if (unlikely(!mm->pgd))
 488                return -ENOMEM;
 489        return 0;
 490}
 491
 492static inline void mm_free_pgd(struct mm_struct *mm)
 493{
 494        pgd_free(mm, mm->pgd);
 495}
 496#else
 497#define dup_mmap(mm, oldmm)     (0)
 498#define mm_alloc_pgd(mm)        (0)
 499#define mm_free_pgd(mm)
 500#endif /* CONFIG_MMU */
 501
 502__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 503
 504#define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 505#define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 506
 507static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 508
 509static int __init coredump_filter_setup(char *s)
 510{
 511        default_dump_filter =
 512                (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 513                MMF_DUMP_FILTER_MASK;
 514        return 1;
 515}
 516
 517__setup("coredump_filter=", coredump_filter_setup);
 518
 519#include <linux/init_task.h>
 520
 521static void mm_init_aio(struct mm_struct *mm)
 522{
 523#ifdef CONFIG_AIO
 524        spin_lock_init(&mm->ioctx_lock);
 525        INIT_HLIST_HEAD(&mm->ioctx_list);
 526#endif
 527}
 528
 529static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
 530{
 531        atomic_set(&mm->mm_users, 1);
 532        atomic_set(&mm->mm_count, 1);
 533        init_rwsem(&mm->mmap_sem);
 534        INIT_LIST_HEAD(&mm->mmlist);
 535        mm->flags = (current->mm) ?
 536                (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
 537        mm->core_state = NULL;
 538        mm->nr_ptes = 0;
 539        memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 540        spin_lock_init(&mm->page_table_lock);
 541        mm_init_aio(mm);
 542        mm_init_owner(mm, p);
 543
 544        if (likely(!mm_alloc_pgd(mm))) {
 545                mm->def_flags = 0;
 546                mmu_notifier_mm_init(mm);
 547                return mm;
 548        }
 549
 550        free_mm(mm);
 551        return NULL;
 552}
 553
 554static void check_mm(struct mm_struct *mm)
 555{
 556        int i;
 557
 558        for (i = 0; i < NR_MM_COUNTERS; i++) {
 559                long x = atomic_long_read(&mm->rss_stat.count[i]);
 560
 561                if (unlikely(x))
 562                        printk(KERN_ALERT "BUG: Bad rss-counter state "
 563                                          "mm:%p idx:%d val:%ld\n", mm, i, x);
 564        }
 565
 566#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 567        VM_BUG_ON(mm->pmd_huge_pte);
 568#endif
 569}
 570
 571/*
 572 * Allocate and initialize an mm_struct.
 573 */
 574struct mm_struct *mm_alloc(void)
 575{
 576        struct mm_struct *mm;
 577
 578        mm = allocate_mm();
 579        if (!mm)
 580                return NULL;
 581
 582        memset(mm, 0, sizeof(*mm));
 583        mm_init_cpumask(mm);
 584        return mm_init(mm, current);
 585}
 586
 587/*
 588 * Called when the last reference to the mm
 589 * is dropped: either by a lazy thread or by
 590 * mmput. Free the page directory and the mm.
 591 */
 592void __mmdrop(struct mm_struct *mm)
 593{
 594        BUG_ON(mm == &init_mm);
 595        mm_free_pgd(mm);
 596        destroy_context(mm);
 597        mmu_notifier_mm_destroy(mm);
 598        check_mm(mm);
 599        free_mm(mm);
 600}
 601EXPORT_SYMBOL_GPL(__mmdrop);
 602
 603/*
 604 * Decrement the use count and release all resources for an mm.
 605 */
 606void mmput(struct mm_struct *mm)
 607{
 608        might_sleep();
 609
 610        if (atomic_dec_and_test(&mm->mm_users)) {
 611                uprobe_clear_state(mm);
 612                exit_aio(mm);
 613                ksm_exit(mm);
 614                khugepaged_exit(mm); /* must run before exit_mmap */
 615                exit_mmap(mm);
 616                set_mm_exe_file(mm, NULL);
 617                if (!list_empty(&mm->mmlist)) {
 618                        spin_lock(&mmlist_lock);
 619                        list_del(&mm->mmlist);
 620                        spin_unlock(&mmlist_lock);
 621                }
 622                if (mm->binfmt)
 623                        module_put(mm->binfmt->module);
 624                mmdrop(mm);
 625        }
 626}
 627EXPORT_SYMBOL_GPL(mmput);
 628
 629void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 630{
 631        if (new_exe_file)
 632                get_file(new_exe_file);
 633        if (mm->exe_file)
 634                fput(mm->exe_file);
 635        mm->exe_file = new_exe_file;
 636}
 637
 638struct file *get_mm_exe_file(struct mm_struct *mm)
 639{
 640        struct file *exe_file;
 641
 642        /* We need mmap_sem to protect against races with removal of exe_file */
 643        down_read(&mm->mmap_sem);
 644        exe_file = mm->exe_file;
 645        if (exe_file)
 646                get_file(exe_file);
 647        up_read(&mm->mmap_sem);
 648        return exe_file;
 649}
 650
 651static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
 652{
 653        /* It's safe to write the exe_file pointer without exe_file_lock because
 654         * this is called during fork when the task is not yet in /proc */
 655        newmm->exe_file = get_mm_exe_file(oldmm);
 656}
 657
 658/**
 659 * get_task_mm - acquire a reference to the task's mm
 660 *
 661 * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 662 * this kernel workthread has transiently adopted a user mm with use_mm,
 663 * to do its AIO) is not set and if so returns a reference to it, after
 664 * bumping up the use count.  User must release the mm via mmput()
 665 * after use.  Typically used by /proc and ptrace.
 666 */
 667struct mm_struct *get_task_mm(struct task_struct *task)
 668{
 669        struct mm_struct *mm;
 670
 671        task_lock(task);
 672        mm = task->mm;
 673        if (mm) {
 674                if (task->flags & PF_KTHREAD)
 675                        mm = NULL;
 676                else
 677                        atomic_inc(&mm->mm_users);
 678        }
 679        task_unlock(task);
 680        return mm;
 681}
 682EXPORT_SYMBOL_GPL(get_task_mm);
 683
 684struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
 685{
 686        struct mm_struct *mm;
 687        int err;
 688
 689        err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
 690        if (err)
 691                return ERR_PTR(err);
 692
 693        mm = get_task_mm(task);
 694        if (mm && mm != current->mm &&
 695                        !ptrace_may_access(task, mode)) {
 696                mmput(mm);
 697                mm = ERR_PTR(-EACCES);
 698        }
 699        mutex_unlock(&task->signal->cred_guard_mutex);
 700
 701        return mm;
 702}
 703
 704static void complete_vfork_done(struct task_struct *tsk)
 705{
 706        struct completion *vfork;
 707
 708        task_lock(tsk);
 709        vfork = tsk->vfork_done;
 710        if (likely(vfork)) {
 711                tsk->vfork_done = NULL;
 712                complete(vfork);
 713        }
 714        task_unlock(tsk);
 715}
 716
 717static int wait_for_vfork_done(struct task_struct *child,
 718                                struct completion *vfork)
 719{
 720        int killed;
 721
 722        freezer_do_not_count();
 723        killed = wait_for_completion_killable(vfork);
 724        freezer_count();
 725
 726        if (killed) {
 727                task_lock(child);
 728                child->vfork_done = NULL;
 729                task_unlock(child);
 730        }
 731
 732        put_task_struct(child);
 733        return killed;
 734}
 735
 736/* Please note the differences between mmput and mm_release.
 737 * mmput is called whenever we stop holding onto a mm_struct,
 738 * error success whatever.
 739 *
 740 * mm_release is called after a mm_struct has been removed
 741 * from the current process.
 742 *
 743 * This difference is important for error handling, when we
 744 * only half set up a mm_struct for a new process and need to restore
 745 * the old one.  Because we mmput the new mm_struct before
 746 * restoring the old one. . .
 747 * Eric Biederman 10 January 1998
 748 */
 749void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 750{
 751        /* Get rid of any futexes when releasing the mm */
 752#ifdef CONFIG_FUTEX
 753        if (unlikely(tsk->robust_list)) {
 754                exit_robust_list(tsk);
 755                tsk->robust_list = NULL;
 756        }
 757#ifdef CONFIG_COMPAT
 758        if (unlikely(tsk->compat_robust_list)) {
 759                compat_exit_robust_list(tsk);
 760                tsk->compat_robust_list = NULL;
 761        }
 762#endif
 763        if (unlikely(!list_empty(&tsk->pi_state_list)))
 764                exit_pi_state_list(tsk);
 765#endif
 766
 767        uprobe_free_utask(tsk);
 768
 769        /* Get rid of any cached register state */
 770        deactivate_mm(tsk, mm);
 771
 772        /*
 773         * If we're exiting normally, clear a user-space tid field if
 774         * requested.  We leave this alone when dying by signal, to leave
 775         * the value intact in a core dump, and to save the unnecessary
 776         * trouble, say, a killed vfork parent shouldn't touch this mm.
 777         * Userland only wants this done for a sys_exit.
 778         */
 779        if (tsk->clear_child_tid) {
 780                if (!(tsk->flags & PF_SIGNALED) &&
 781                    atomic_read(&mm->mm_users) > 1) {
 782                        /*
 783                         * We don't check the error code - if userspace has
 784                         * not set up a proper pointer then tough luck.
 785                         */
 786                        put_user(0, tsk->clear_child_tid);
 787                        sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
 788                                        1, NULL, NULL, 0);
 789                }
 790                tsk->clear_child_tid = NULL;
 791        }
 792
 793        /*
 794         * All done, finally we can wake up parent and return this mm to him.
 795         * Also kthread_stop() uses this completion for synchronization.
 796         */
 797        if (tsk->vfork_done)
 798                complete_vfork_done(tsk);
 799}
 800
 801/*
 802 * Allocate a new mm structure and copy contents from the
 803 * mm structure of the passed in task structure.
 804 */
 805struct mm_struct *dup_mm(struct task_struct *tsk)
 806{
 807        struct mm_struct *mm, *oldmm = current->mm;
 808        int err;
 809
 810        if (!oldmm)
 811                return NULL;
 812
 813        mm = allocate_mm();
 814        if (!mm)
 815                goto fail_nomem;
 816
 817        memcpy(mm, oldmm, sizeof(*mm));
 818        mm_init_cpumask(mm);
 819
 820#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 821        mm->pmd_huge_pte = NULL;
 822#endif
 823#ifdef CONFIG_NUMA_BALANCING
 824        mm->first_nid = NUMA_PTE_SCAN_INIT;
 825#endif
 826        if (!mm_init(mm, tsk))
 827                goto fail_nomem;
 828
 829        if (init_new_context(tsk, mm))
 830                goto fail_nocontext;
 831
 832        dup_mm_exe_file(oldmm, mm);
 833
 834        err = dup_mmap(mm, oldmm);
 835        if (err)
 836                goto free_pt;
 837
 838        mm->hiwater_rss = get_mm_rss(mm);
 839        mm->hiwater_vm = mm->total_vm;
 840
 841        if (mm->binfmt && !try_module_get(mm->binfmt->module))
 842                goto free_pt;
 843
 844        return mm;
 845
 846free_pt:
 847        /* don't put binfmt in mmput, we haven't got module yet */
 848        mm->binfmt = NULL;
 849        mmput(mm);
 850
 851fail_nomem:
 852        return NULL;
 853
 854fail_nocontext:
 855        /*
 856         * If init_new_context() failed, we cannot use mmput() to free the mm
 857         * because it calls destroy_context()
 858         */
 859        mm_free_pgd(mm);
 860        free_mm(mm);
 861        return NULL;
 862}
 863
 864static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
 865{
 866        struct mm_struct *mm, *oldmm;
 867        int retval;
 868
 869        tsk->min_flt = tsk->maj_flt = 0;
 870        tsk->nvcsw = tsk->nivcsw = 0;
 871#ifdef CONFIG_DETECT_HUNG_TASK
 872        tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 873#endif
 874
 875        tsk->mm = NULL;
 876        tsk->active_mm = NULL;
 877
 878        /*
 879         * Are we cloning a kernel thread?
 880         *
 881         * We need to steal a active VM for that..
 882         */
 883        oldmm = current->mm;
 884        if (!oldmm)
 885                return 0;
 886
 887        if (clone_flags & CLONE_VM) {
 888                atomic_inc(&oldmm->mm_users);
 889                mm = oldmm;
 890                goto good_mm;
 891        }
 892
 893        retval = -ENOMEM;
 894        mm = dup_mm(tsk);
 895        if (!mm)
 896                goto fail_nomem;
 897
 898good_mm:
 899        tsk->mm = mm;
 900        tsk->active_mm = mm;
 901        return 0;
 902
 903fail_nomem:
 904        return retval;
 905}
 906
 907static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 908{
 909        struct fs_struct *fs = current->fs;
 910        if (clone_flags & CLONE_FS) {
 911                /* tsk->fs is already what we want */
 912                spin_lock(&fs->lock);
 913                if (fs->in_exec) {
 914                        spin_unlock(&fs->lock);
 915                        return -EAGAIN;
 916                }
 917                fs->users++;
 918                spin_unlock(&fs->lock);
 919                return 0;
 920        }
 921        tsk->fs = copy_fs_struct(fs);
 922        if (!tsk->fs)
 923                return -ENOMEM;
 924        return 0;
 925}
 926
 927static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
 928{
 929        struct files_struct *oldf, *newf;
 930        int error = 0;
 931
 932        /*
 933         * A background process may not have any files ...
 934         */
 935        oldf = current->files;
 936        if (!oldf)
 937                goto out;
 938
 939        if (clone_flags & CLONE_FILES) {
 940                atomic_inc(&oldf->count);
 941                goto out;
 942        }
 943
 944        newf = dup_fd(oldf, &error);
 945        if (!newf)
 946                goto out;
 947
 948        tsk->files = newf;
 949        error = 0;
 950out:
 951        return error;
 952}
 953
 954static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 955{
 956#ifdef CONFIG_BLOCK
 957        struct io_context *ioc = current->io_context;
 958        struct io_context *new_ioc;
 959
 960        if (!ioc)
 961                return 0;
 962        /*
 963         * Share io context with parent, if CLONE_IO is set
 964         */
 965        if (clone_flags & CLONE_IO) {
 966                ioc_task_link(ioc);
 967                tsk->io_context = ioc;
 968        } else if (ioprio_valid(ioc->ioprio)) {
 969                new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
 970                if (unlikely(!new_ioc))
 971                        return -ENOMEM;
 972
 973                new_ioc->ioprio = ioc->ioprio;
 974                put_io_context(new_ioc);
 975        }
 976#endif
 977        return 0;
 978}
 979
 980static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 981{
 982        struct sighand_struct *sig;
 983
 984        if (clone_flags & CLONE_SIGHAND) {
 985                atomic_inc(&current->sighand->count);
 986                return 0;
 987        }
 988        sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 989        rcu_assign_pointer(tsk->sighand, sig);
 990        if (!sig)
 991                return -ENOMEM;
 992        atomic_set(&sig->count, 1);
 993        memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 994        return 0;
 995}
 996
 997void __cleanup_sighand(struct sighand_struct *sighand)
 998{
 999        if (atomic_dec_and_test(&sighand->count)) {
1000                signalfd_cleanup(sighand);
1001                kmem_cache_free(sighand_cachep, sighand);
1002        }
1003}
1004
1005
1006/*
1007 * Initialize POSIX timer handling for a thread group.
1008 */
1009static void posix_cpu_timers_init_group(struct signal_struct *sig)
1010{
1011        unsigned long cpu_limit;
1012
1013        /* Thread group counters. */
1014        thread_group_cputime_init(sig);
1015
1016        cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1017        if (cpu_limit != RLIM_INFINITY) {
1018                sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1019                sig->cputimer.running = 1;
1020        }
1021
1022        /* The timer lists. */
1023        INIT_LIST_HEAD(&sig->cpu_timers[0]);
1024        INIT_LIST_HEAD(&sig->cpu_timers[1]);
1025        INIT_LIST_HEAD(&sig->cpu_timers[2]);
1026}
1027
1028static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1029{
1030        struct signal_struct *sig;
1031
1032        if (clone_flags & CLONE_THREAD)
1033                return 0;
1034
1035        sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1036        tsk->signal = sig;
1037        if (!sig)
1038                return -ENOMEM;
1039
1040        sig->nr_threads = 1;
1041        atomic_set(&sig->live, 1);
1042        atomic_set(&sig->sigcnt, 1);
1043        init_waitqueue_head(&sig->wait_chldexit);
1044        sig->curr_target = tsk;
1045        init_sigpending(&sig->shared_pending);
1046        INIT_LIST_HEAD(&sig->posix_timers);
1047
1048        hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1049        sig->real_timer.function = it_real_fn;
1050
1051        task_lock(current->group_leader);
1052        memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1053        task_unlock(current->group_leader);
1054
1055        posix_cpu_timers_init_group(sig);
1056
1057        tty_audit_fork(sig);
1058        sched_autogroup_fork(sig);
1059
1060#ifdef CONFIG_CGROUPS
1061        init_rwsem(&sig->group_rwsem);
1062#endif
1063
1064        sig->oom_score_adj = current->signal->oom_score_adj;
1065        sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1066
1067        sig->has_child_subreaper = current->signal->has_child_subreaper ||
1068                                   current->signal->is_child_subreaper;
1069
1070        mutex_init(&sig->cred_guard_mutex);
1071
1072        return 0;
1073}
1074
1075static void copy_flags(unsigned long clone_flags, struct task_struct *p)
1076{
1077        unsigned long new_flags = p->flags;
1078
1079        new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1080        new_flags |= PF_FORKNOEXEC;
1081        p->flags = new_flags;
1082}
1083
1084SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1085{
1086        current->clear_child_tid = tidptr;
1087
1088        return task_pid_vnr(current);
1089}
1090
1091static void rt_mutex_init_task(struct task_struct *p)
1092{
1093        raw_spin_lock_init(&p->pi_lock);
1094#ifdef CONFIG_RT_MUTEXES
1095        plist_head_init(&p->pi_waiters);
1096        p->pi_blocked_on = NULL;
1097#endif
1098}
1099
1100#ifdef CONFIG_MM_OWNER
1101void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1102{
1103        mm->owner = p;
1104}
1105#endif /* CONFIG_MM_OWNER */
1106
1107/*
1108 * Initialize POSIX timer handling for a single task.
1109 */
1110static void posix_cpu_timers_init(struct task_struct *tsk)
1111{
1112        tsk->cputime_expires.prof_exp = 0;
1113        tsk->cputime_expires.virt_exp = 0;
1114        tsk->cputime_expires.sched_exp = 0;
1115        INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1116        INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1117        INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1118}
1119
1120static inline void
1121init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1122{
1123         task->pids[type].pid = pid;
1124}
1125
1126/*
1127 * This creates a new process as a copy of the old one,
1128 * but does not actually start it yet.
1129 *
1130 * It copies the registers, and all the appropriate
1131 * parts of the process environment (as per the clone
1132 * flags). The actual kick-off is left to the caller.
1133 */
1134static struct task_struct *copy_process(unsigned long clone_flags,
1135                                        unsigned long stack_start,
1136                                        unsigned long stack_size,
1137                                        int __user *child_tidptr,
1138                                        struct pid *pid,
1139                                        int trace)
1140{
1141        int retval;
1142        struct task_struct *p;
1143
1144        if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1145                return ERR_PTR(-EINVAL);
1146
1147        if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1148                return ERR_PTR(-EINVAL);
1149
1150        /*
1151         * Thread groups must share signals as well, and detached threads
1152         * can only be started up within the thread group.
1153         */
1154        if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1155                return ERR_PTR(-EINVAL);
1156
1157        /*
1158         * Shared signal handlers imply shared VM. By way of the above,
1159         * thread groups also imply shared VM. Blocking this case allows
1160         * for various simplifications in other code.
1161         */
1162        if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1163                return ERR_PTR(-EINVAL);
1164
1165        /*
1166         * Siblings of global init remain as zombies on exit since they are
1167         * not reaped by their parent (swapper). To solve this and to avoid
1168         * multi-rooted process trees, prevent global and container-inits
1169         * from creating siblings.
1170         */
1171        if ((clone_flags & CLONE_PARENT) &&
1172                                current->signal->flags & SIGNAL_UNKILLABLE)
1173                return ERR_PTR(-EINVAL);
1174
1175        /*
1176         * If the new process will be in a different pid namespace don't
1177         * allow it to share a thread group or signal handlers with the
1178         * forking task.
1179         */
1180        if ((clone_flags & (CLONE_SIGHAND | CLONE_NEWPID)) &&
1181            (task_active_pid_ns(current) !=
1182             current->nsproxy->pid_ns_for_children))
1183                return ERR_PTR(-EINVAL);
1184
1185        retval = security_task_create(clone_flags);
1186        if (retval)
1187                goto fork_out;
1188
1189        retval = -ENOMEM;
1190        p = dup_task_struct(current);
1191        if (!p)
1192                goto fork_out;
1193
1194        ftrace_graph_init_task(p);
1195        get_seccomp_filter(p);
1196
1197        rt_mutex_init_task(p);
1198
1199#ifdef CONFIG_PROVE_LOCKING
1200        DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1201        DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1202#endif
1203        retval = -EAGAIN;
1204        if (atomic_read(&p->real_cred->user->processes) >=
1205                        task_rlimit(p, RLIMIT_NPROC)) {
1206                if (p->real_cred->user != INIT_USER &&
1207                    !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1208                        goto bad_fork_free;
1209        }
1210        current->flags &= ~PF_NPROC_EXCEEDED;
1211
1212        retval = copy_creds(p, clone_flags);
1213        if (retval < 0)
1214                goto bad_fork_free;
1215
1216        /*
1217         * If multiple threads are within copy_process(), then this check
1218         * triggers too late. This doesn't hurt, the check is only there
1219         * to stop root fork bombs.
1220         */
1221        retval = -EAGAIN;
1222        if (nr_threads >= max_threads)
1223                goto bad_fork_cleanup_count;
1224
1225        if (!try_module_get(task_thread_info(p)->exec_domain->module))
1226                goto bad_fork_cleanup_count;
1227
1228        p->did_exec = 0;
1229        delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1230        copy_flags(clone_flags, p);
1231        INIT_LIST_HEAD(&p->children);
1232        INIT_LIST_HEAD(&p->sibling);
1233        rcu_copy_process(p);
1234        p->vfork_done = NULL;
1235        spin_lock_init(&p->alloc_lock);
1236
1237        init_sigpending(&p->pending);
1238
1239        p->utime = p->stime = p->gtime = 0;
1240        p->utimescaled = p->stimescaled = 0;
1241#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
1242        p->prev_cputime.utime = p->prev_cputime.stime = 0;
1243#endif
1244#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1245        seqlock_init(&p->vtime_seqlock);
1246        p->vtime_snap = 0;
1247        p->vtime_snap_whence = VTIME_SLEEPING;
1248#endif
1249
1250#if defined(SPLIT_RSS_COUNTING)
1251        memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1252#endif
1253
1254        p->default_timer_slack_ns = current->timer_slack_ns;
1255
1256        task_io_accounting_init(&p->ioac);
1257        acct_clear_integrals(p);
1258
1259        posix_cpu_timers_init(p);
1260
1261        do_posix_clock_monotonic_gettime(&p->start_time);
1262        p->real_start_time = p->start_time;
1263        monotonic_to_bootbased(&p->real_start_time);
1264        p->io_context = NULL;
1265        p->audit_context = NULL;
1266        if (clone_flags & CLONE_THREAD)
1267                threadgroup_change_begin(current);
1268        cgroup_fork(p);
1269#ifdef CONFIG_NUMA
1270        p->mempolicy = mpol_dup(p->mempolicy);
1271        if (IS_ERR(p->mempolicy)) {
1272                retval = PTR_ERR(p->mempolicy);
1273                p->mempolicy = NULL;
1274                goto bad_fork_cleanup_cgroup;
1275        }
1276        mpol_fix_fork_child_flag(p);
1277#endif
1278#ifdef CONFIG_CPUSETS
1279        p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1280        p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1281        seqcount_init(&p->mems_allowed_seq);
1282#endif
1283#ifdef CONFIG_TRACE_IRQFLAGS
1284        p->irq_events = 0;
1285        p->hardirqs_enabled = 0;
1286        p->hardirq_enable_ip = 0;
1287        p->hardirq_enable_event = 0;
1288        p->hardirq_disable_ip = _THIS_IP_;
1289        p->hardirq_disable_event = 0;
1290        p->softirqs_enabled = 1;
1291        p->softirq_enable_ip = _THIS_IP_;
1292        p->softirq_enable_event = 0;
1293        p->softirq_disable_ip = 0;
1294        p->softirq_disable_event = 0;
1295        p->hardirq_context = 0;
1296        p->softirq_context = 0;
1297#endif
1298#ifdef CONFIG_LOCKDEP
1299        p->lockdep_depth = 0; /* no locks held yet */
1300        p->curr_chain_key = 0;
1301        p->lockdep_recursion = 0;
1302#endif
1303
1304#ifdef CONFIG_DEBUG_MUTEXES
1305        p->blocked_on = NULL; /* not blocked yet */
1306#endif
1307#ifdef CONFIG_MEMCG
1308        p->memcg_batch.do_batch = 0;
1309        p->memcg_batch.memcg = NULL;
1310#endif
1311#ifdef CONFIG_BCACHE
1312        p->sequential_io        = 0;
1313        p->sequential_io_avg    = 0;
1314#endif
1315
1316        /* Perform scheduler related setup. Assign this task to a CPU. */
1317        sched_fork(p);
1318
1319        retval = perf_event_init_task(p);
1320        if (retval)
1321                goto bad_fork_cleanup_policy;
1322        retval = audit_alloc(p);
1323        if (retval)
1324                goto bad_fork_cleanup_policy;
1325        /* copy all the process information */
1326        retval = copy_semundo(clone_flags, p);
1327        if (retval)
1328                goto bad_fork_cleanup_audit;
1329        retval = copy_files(clone_flags, p);
1330        if (retval)
1331                goto bad_fork_cleanup_semundo;
1332        retval = copy_fs(clone_flags, p);
1333        if (retval)
1334                goto bad_fork_cleanup_files;
1335        retval = copy_sighand(clone_flags, p);
1336        if (retval)
1337                goto bad_fork_cleanup_fs;
1338        retval = copy_signal(clone_flags, p);
1339        if (retval)
1340                goto bad_fork_cleanup_sighand;
1341        retval = copy_mm(clone_flags, p);
1342        if (retval)
1343                goto bad_fork_cleanup_signal;
1344        retval = copy_namespaces(clone_flags, p);
1345        if (retval)
1346                goto bad_fork_cleanup_mm;
1347        retval = copy_io(clone_flags, p);
1348        if (retval)
1349                goto bad_fork_cleanup_namespaces;
1350        retval = copy_thread(clone_flags, stack_start, stack_size, p);
1351        if (retval)
1352                goto bad_fork_cleanup_io;
1353
1354        if (pid != &init_struct_pid) {
1355                retval = -ENOMEM;
1356                pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1357                if (!pid)
1358                        goto bad_fork_cleanup_io;
1359        }
1360
1361        p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1362        /*
1363         * Clear TID on mm_release()?
1364         */
1365        p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1366#ifdef CONFIG_BLOCK
1367        p->plug = NULL;
1368#endif
1369#ifdef CONFIG_FUTEX
1370        p->robust_list = NULL;
1371#ifdef CONFIG_COMPAT
1372        p->compat_robust_list = NULL;
1373#endif
1374        INIT_LIST_HEAD(&p->pi_state_list);
1375        p->pi_state_cache = NULL;
1376#endif
1377        uprobe_copy_process(p);
1378        /*
1379         * sigaltstack should be cleared when sharing the same VM
1380         */
1381        if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1382                p->sas_ss_sp = p->sas_ss_size = 0;
1383
1384        /*
1385         * Syscall tracing and stepping should be turned off in the
1386         * child regardless of CLONE_PTRACE.
1387         */
1388        user_disable_single_step(p);
1389        clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1390#ifdef TIF_SYSCALL_EMU
1391        clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1392#endif
1393        clear_all_latency_tracing(p);
1394
1395        /* ok, now we should be set up.. */
1396        p->pid = pid_nr(pid);
1397        if (clone_flags & CLONE_THREAD) {
1398                p->exit_signal = -1;
1399                p->group_leader = current->group_leader;
1400                p->tgid = current->tgid;
1401        } else {
1402                if (clone_flags & CLONE_PARENT)
1403                        p->exit_signal = current->group_leader->exit_signal;
1404                else
1405                        p->exit_signal = (clone_flags & CSIGNAL);
1406                p->group_leader = p;
1407                p->tgid = p->pid;
1408        }
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        INIT_LIST_HEAD(&p->thread_group);
1418        p->task_works = NULL;
1419
1420        /*
1421         * Make it visible to the rest of the system, but dont wake it up yet.
1422         * Need tasklist lock for parent etc handling!
1423         */
1424        write_lock_irq(&tasklist_lock);
1425
1426        /* CLONE_PARENT re-uses the old parent */
1427        if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1428                p->real_parent = current->real_parent;
1429                p->parent_exec_id = current->parent_exec_id;
1430        } else {
1431                p->real_parent = current;
1432                p->parent_exec_id = current->self_exec_id;
1433        }
1434
1435        spin_lock(&current->sighand->siglock);
1436
1437        /*
1438         * Process group and session signals need to be delivered to just the
1439         * parent before the fork or both the parent and the child after the
1440         * fork. Restart if a signal comes in before we add the new process to
1441         * it's process group.
1442         * A fatal signal pending means that current will exit, so the new
1443         * thread can't slip out of an OOM kill (or normal SIGKILL).
1444        */
1445        recalc_sigpending();
1446        if (signal_pending(current)) {
1447                spin_unlock(&current->sighand->siglock);
1448                write_unlock_irq(&tasklist_lock);
1449                retval = -ERESTARTNOINTR;
1450                goto bad_fork_free_pid;
1451        }
1452
1453        if (likely(p->pid)) {
1454                ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1455
1456                init_task_pid(p, PIDTYPE_PID, pid);
1457                if (thread_group_leader(p)) {
1458                        init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1459                        init_task_pid(p, PIDTYPE_SID, task_session(current));
1460
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                        list_add_tail(&p->sibling, &p->real_parent->children);
1469                        list_add_tail_rcu(&p->tasks, &init_task.tasks);
1470                        attach_pid(p, PIDTYPE_PGID);
1471                        attach_pid(p, PIDTYPE_SID);
1472                        __this_cpu_inc(process_counts);
1473                } else {
1474                        current->signal->nr_threads++;
1475                        atomic_inc(&current->signal->live);
1476                        atomic_inc(&current->signal->sigcnt);
1477                        list_add_tail_rcu(&p->thread_group,
1478                                          &p->group_leader->thread_group);
1479                }
1480                attach_pid(p, PIDTYPE_PID);
1481                nr_threads++;
1482        }
1483
1484        total_forks++;
1485        spin_unlock(&current->sighand->siglock);
1486        write_unlock_irq(&tasklist_lock);
1487        proc_fork_connector(p);
1488        cgroup_post_fork(p);
1489        if (clone_flags & CLONE_THREAD)
1490                threadgroup_change_end(current);
1491        perf_event_fork(p);
1492
1493        trace_task_newtask(p, clone_flags);
1494
1495        return p;
1496
1497bad_fork_free_pid:
1498        if (pid != &init_struct_pid)
1499                free_pid(pid);
1500bad_fork_cleanup_io:
1501        if (p->io_context)
1502                exit_io_context(p);
1503bad_fork_cleanup_namespaces:
1504        exit_task_namespaces(p);
1505bad_fork_cleanup_mm:
1506        if (p->mm)
1507                mmput(p->mm);
1508bad_fork_cleanup_signal:
1509        if (!(clone_flags & CLONE_THREAD))
1510                free_signal_struct(p->signal);
1511bad_fork_cleanup_sighand:
1512        __cleanup_sighand(p->sighand);
1513bad_fork_cleanup_fs:
1514        exit_fs(p); /* blocking */
1515bad_fork_cleanup_files:
1516        exit_files(p); /* blocking */
1517bad_fork_cleanup_semundo:
1518        exit_sem(p);
1519bad_fork_cleanup_audit:
1520        audit_free(p);
1521bad_fork_cleanup_policy:
1522        perf_event_free_task(p);
1523#ifdef CONFIG_NUMA
1524        mpol_put(p->mempolicy);
1525bad_fork_cleanup_cgroup:
1526#endif
1527        if (clone_flags & CLONE_THREAD)
1528                threadgroup_change_end(current);
1529        cgroup_exit(p, 0);
1530        delayacct_tsk_free(p);
1531        module_put(task_thread_info(p)->exec_domain->module);
1532bad_fork_cleanup_count:
1533        atomic_dec(&p->cred->user->processes);
1534        exit_creds(p);
1535bad_fork_free:
1536        free_task(p);
1537fork_out:
1538        return ERR_PTR(retval);
1539}
1540
1541static inline void init_idle_pids(struct pid_link *links)
1542{
1543        enum pid_type type;
1544
1545        for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1546                INIT_HLIST_NODE(&links[type].node); /* not really needed */
1547                links[type].pid = &init_struct_pid;
1548        }
1549}
1550
1551struct task_struct *fork_idle(int cpu)
1552{
1553        struct task_struct *task;
1554        task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0);
1555        if (!IS_ERR(task)) {
1556                init_idle_pids(task->pids);
1557                init_idle(task, cpu);
1558        }
1559
1560        return task;
1561}
1562
1563/*
1564 *  Ok, this is the main fork-routine.
1565 *
1566 * It copies the process, and if successful kick-starts
1567 * it and waits for it to finish using the VM if required.
1568 */
1569long do_fork(unsigned long clone_flags,
1570              unsigned long stack_start,
1571              unsigned long stack_size,
1572              int __user *parent_tidptr,
1573              int __user *child_tidptr)
1574{
1575        struct task_struct *p;
1576        int trace = 0;
1577        long nr;
1578
1579        /*
1580         * Do some preliminary argument and permissions checking before we
1581         * actually start allocating stuff
1582         */
1583        if (clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) {
1584                if (clone_flags & (CLONE_THREAD|CLONE_PARENT))
1585                        return -EINVAL;
1586        }
1587
1588        /*
1589         * Determine whether and which event to report to ptracer.  When
1590         * called from kernel_thread or CLONE_UNTRACED is explicitly
1591         * requested, no event is reported; otherwise, report if the event
1592         * for the type of forking is enabled.
1593         */
1594        if (!(clone_flags & CLONE_UNTRACED)) {
1595                if (clone_flags & CLONE_VFORK)
1596                        trace = PTRACE_EVENT_VFORK;
1597                else if ((clone_flags & CSIGNAL) != SIGCHLD)
1598                        trace = PTRACE_EVENT_CLONE;
1599                else
1600                        trace = PTRACE_EVENT_FORK;
1601
1602                if (likely(!ptrace_event_enabled(current, trace)))
1603                        trace = 0;
1604        }
1605
1606        p = copy_process(clone_flags, stack_start, stack_size,
1607                         child_tidptr, NULL, trace);
1608        /*
1609         * Do this prior waking up the new thread - the thread pointer
1610         * might get invalid after that point, if the thread exits quickly.
1611         */
1612        if (!IS_ERR(p)) {
1613                struct completion vfork;
1614
1615                trace_sched_process_fork(current, p);
1616
1617                nr = task_pid_vnr(p);
1618
1619                if (clone_flags & CLONE_PARENT_SETTID)
1620                        put_user(nr, parent_tidptr);
1621
1622                if (clone_flags & CLONE_VFORK) {
1623                        p->vfork_done = &vfork;
1624                        init_completion(&vfork);
1625                        get_task_struct(p);
1626                }
1627
1628                wake_up_new_task(p);
1629
1630                /* forking complete and child started to run, tell ptracer */
1631                if (unlikely(trace))
1632                        ptrace_event(trace, nr);
1633
1634                if (clone_flags & CLONE_VFORK) {
1635                        if (!wait_for_vfork_done(p, &vfork))
1636                                ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1637                }
1638        } else {
1639                nr = PTR_ERR(p);
1640        }
1641        return nr;
1642}
1643
1644/*
1645 * Create a kernel thread.
1646 */
1647pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
1648{
1649        return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
1650                (unsigned long)arg, NULL, NULL);
1651}
1652
1653#ifdef __ARCH_WANT_SYS_FORK
1654SYSCALL_DEFINE0(fork)
1655{
1656#ifdef CONFIG_MMU
1657        return do_fork(SIGCHLD, 0, 0, NULL, NULL);
1658#else
1659        /* can not support in nommu mode */
1660        return(-EINVAL);
1661#endif
1662}
1663#endif
1664
1665#ifdef __ARCH_WANT_SYS_VFORK
1666SYSCALL_DEFINE0(vfork)
1667{
1668        return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 
1669                        0, NULL, NULL);
1670}
1671#endif
1672
1673#ifdef __ARCH_WANT_SYS_CLONE
1674#ifdef CONFIG_CLONE_BACKWARDS
1675SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1676                 int __user *, parent_tidptr,
1677                 int, tls_val,
1678                 int __user *, child_tidptr)
1679#elif defined(CONFIG_CLONE_BACKWARDS2)
1680SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
1681                 int __user *, parent_tidptr,
1682                 int __user *, child_tidptr,
1683                 int, tls_val)
1684#elif defined(CONFIG_CLONE_BACKWARDS3)
1685SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
1686                int, stack_size,
1687                int __user *, parent_tidptr,
1688                int __user *, child_tidptr,
1689                int, tls_val)
1690#else
1691SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1692                 int __user *, parent_tidptr,
1693                 int __user *, child_tidptr,
1694                 int, tls_val)
1695#endif
1696{
1697        return do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr);
1698}
1699#endif
1700
1701#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1702#define ARCH_MIN_MMSTRUCT_ALIGN 0
1703#endif
1704
1705static void sighand_ctor(void *data)
1706{
1707        struct sighand_struct *sighand = data;
1708
1709        spin_lock_init(&sighand->siglock);
1710        init_waitqueue_head(&sighand->signalfd_wqh);
1711}
1712
1713void __init proc_caches_init(void)
1714{
1715        sighand_cachep = kmem_cache_create("sighand_cache",
1716                        sizeof(struct sighand_struct), 0,
1717                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1718                        SLAB_NOTRACK, sighand_ctor);
1719        signal_cachep = kmem_cache_create("signal_cache",
1720                        sizeof(struct signal_struct), 0,
1721                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1722        files_cachep = kmem_cache_create("files_cache",
1723                        sizeof(struct files_struct), 0,
1724                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1725        fs_cachep = kmem_cache_create("fs_cache",
1726                        sizeof(struct fs_struct), 0,
1727                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1728        /*
1729         * FIXME! The "sizeof(struct mm_struct)" currently includes the
1730         * whole struct cpumask for the OFFSTACK case. We could change
1731         * this to *only* allocate as much of it as required by the
1732         * maximum number of CPU's we can ever have.  The cpumask_allocation
1733         * is at the end of the structure, exactly for that reason.
1734         */
1735        mm_cachep = kmem_cache_create("mm_struct",
1736                        sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1737                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1738        vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1739        mmap_init();
1740        nsproxy_cache_init();
1741}
1742
1743/*
1744 * Check constraints on flags passed to the unshare system call.
1745 */
1746static int check_unshare_flags(unsigned long unshare_flags)
1747{
1748        if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1749                                CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1750                                CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
1751                                CLONE_NEWUSER|CLONE_NEWPID))
1752                return -EINVAL;
1753        /*
1754         * Not implemented, but pretend it works if there is nothing to
1755         * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1756         * needs to unshare vm.
1757         */
1758        if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1759                /* FIXME: get_task_mm() increments ->mm_users */
1760                if (atomic_read(&current->mm->mm_users) > 1)
1761                        return -EINVAL;
1762        }
1763
1764        return 0;
1765}
1766
1767/*
1768 * Unshare the filesystem structure if it is being shared
1769 */
1770static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1771{
1772        struct fs_struct *fs = current->fs;
1773
1774        if (!(unshare_flags & CLONE_FS) || !fs)
1775                return 0;
1776
1777        /* don't need lock here; in the worst case we'll do useless copy */
1778        if (fs->users == 1)
1779                return 0;
1780
1781        *new_fsp = copy_fs_struct(fs);
1782        if (!*new_fsp)
1783                return -ENOMEM;
1784
1785        return 0;
1786}
1787
1788/*
1789 * Unshare file descriptor table if it is being shared
1790 */
1791static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1792{
1793        struct files_struct *fd = current->files;
1794        int error = 0;
1795
1796        if ((unshare_flags & CLONE_FILES) &&
1797            (fd && atomic_read(&fd->count) > 1)) {
1798                *new_fdp = dup_fd(fd, &error);
1799                if (!*new_fdp)
1800                        return error;
1801        }
1802
1803        return 0;
1804}
1805
1806/*
1807 * unshare allows a process to 'unshare' part of the process
1808 * context which was originally shared using clone.  copy_*
1809 * functions used by do_fork() cannot be used here directly
1810 * because they modify an inactive task_struct that is being
1811 * constructed. Here we are modifying the current, active,
1812 * task_struct.
1813 */
1814SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1815{
1816        struct fs_struct *fs, *new_fs = NULL;
1817        struct files_struct *fd, *new_fd = NULL;
1818        struct cred *new_cred = NULL;
1819        struct nsproxy *new_nsproxy = NULL;
1820        int do_sysvsem = 0;
1821        int err;
1822
1823        /*
1824         * If unsharing a user namespace must also unshare the thread.
1825         */
1826        if (unshare_flags & CLONE_NEWUSER)
1827                unshare_flags |= CLONE_THREAD | CLONE_FS;
1828        /*
1829         * If unsharing a pid namespace must also unshare the thread.
1830         */
1831        if (unshare_flags & CLONE_NEWPID)
1832                unshare_flags |= CLONE_THREAD;
1833        /*
1834         * If unsharing a thread from a thread group, must also unshare vm.
1835         */
1836        if (unshare_flags & CLONE_THREAD)
1837                unshare_flags |= CLONE_VM;
1838        /*
1839         * If unsharing vm, must also unshare signal handlers.
1840         */
1841        if (unshare_flags & CLONE_VM)
1842                unshare_flags |= CLONE_SIGHAND;
1843        /*
1844         * If unsharing namespace, must also unshare filesystem information.
1845         */
1846        if (unshare_flags & CLONE_NEWNS)
1847                unshare_flags |= CLONE_FS;
1848
1849        err = check_unshare_flags(unshare_flags);
1850        if (err)
1851                goto bad_unshare_out;
1852        /*
1853         * CLONE_NEWIPC must also detach from the undolist: after switching
1854         * to a new ipc namespace, the semaphore arrays from the old
1855         * namespace are unreachable.
1856         */
1857        if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1858                do_sysvsem = 1;
1859        err = unshare_fs(unshare_flags, &new_fs);
1860        if (err)
1861                goto bad_unshare_out;
1862        err = unshare_fd(unshare_flags, &new_fd);
1863        if (err)
1864                goto bad_unshare_cleanup_fs;
1865        err = unshare_userns(unshare_flags, &new_cred);
1866        if (err)
1867                goto bad_unshare_cleanup_fd;
1868        err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1869                                         new_cred, new_fs);
1870        if (err)
1871                goto bad_unshare_cleanup_cred;
1872
1873        if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
1874                if (do_sysvsem) {
1875                        /*
1876                         * CLONE_SYSVSEM is equivalent to sys_exit().
1877                         */
1878                        exit_sem(current);
1879                }
1880
1881                if (new_nsproxy)
1882                        switch_task_namespaces(current, new_nsproxy);
1883
1884                task_lock(current);
1885
1886                if (new_fs) {
1887                        fs = current->fs;
1888                        spin_lock(&fs->lock);
1889                        current->fs = new_fs;
1890                        if (--fs->users)
1891                                new_fs = NULL;
1892                        else
1893                                new_fs = fs;
1894                        spin_unlock(&fs->lock);
1895                }
1896
1897                if (new_fd) {
1898                        fd = current->files;
1899                        current->files = new_fd;
1900                        new_fd = fd;
1901                }
1902
1903                task_unlock(current);
1904
1905                if (new_cred) {
1906                        /* Install the new user namespace */
1907                        commit_creds(new_cred);
1908                        new_cred = NULL;
1909                }
1910        }
1911
1912bad_unshare_cleanup_cred:
1913        if (new_cred)
1914                put_cred(new_cred);
1915bad_unshare_cleanup_fd:
1916        if (new_fd)
1917                put_files_struct(new_fd);
1918
1919bad_unshare_cleanup_fs:
1920        if (new_fs)
1921                free_fs_struct(new_fs);
1922
1923bad_unshare_out:
1924        return err;
1925}
1926
1927/*
1928 *      Helper to unshare the files of the current task.
1929 *      We don't want to expose copy_files internals to
1930 *      the exec layer of the kernel.
1931 */
1932
1933int unshare_files(struct files_struct **displaced)
1934{
1935        struct task_struct *task = current;
1936        struct files_struct *copy = NULL;
1937        int error;
1938
1939        error = unshare_fd(CLONE_FILES, &copy);
1940        if (error || !copy) {
1941                *displaced = NULL;
1942                return error;
1943        }
1944        *displaced = task->files;
1945        task_lock(task);
1946        task->files = copy;
1947        task_unlock(task);
1948        return 0;
1949}
1950
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