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