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 <linux/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_stack(unsigned long *stack)
 152{
 153}
 154
 155#ifndef CONFIG_ARCH_THREAD_STACK_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 || defined(CONFIG_VMAP_STACK)
 162
 163#ifdef CONFIG_VMAP_STACK
 164/*
 165 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
 166 * flush.  Try to minimize the number of calls by caching stacks.
 167 */
 168#define NR_CACHED_STACKS 2
 169static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 170#endif
 171
 172static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
 173{
 174#ifdef CONFIG_VMAP_STACK
 175	void *stack;
 176	int i;
 177
 178	local_irq_disable();
 179	for (i = 0; i < NR_CACHED_STACKS; i++) {
 180		struct vm_struct *s = this_cpu_read(cached_stacks[i]);
 
 
 181
 182		if (!s)
 183			continue;
 184		this_cpu_write(cached_stacks[i], NULL);
 
 
 
 
 
 185
 186		tsk->stack_vm_area = s;
 187		local_irq_enable();
 188		return s->addr;
 189	}
 190	local_irq_enable();
 191
 192	stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE,
 
 
 
 
 
 193				     VMALLOC_START, VMALLOC_END,
 194				     THREADINFO_GFP | __GFP_HIGHMEM,
 195				     PAGE_KERNEL,
 196				     0, node, __builtin_return_address(0));
 197
 198	/*
 199	 * We can't call find_vm_area() in interrupt context, and
 200	 * free_thread_stack() can be called in interrupt context,
 201	 * so cache the vm_struct.
 202	 */
 203	if (stack)
 204		tsk->stack_vm_area = find_vm_area(stack);
 
 
 205	return stack;
 206#else
 207	struct page *page = alloc_pages_node(node, THREADINFO_GFP,
 208					     THREAD_SIZE_ORDER);
 209
 210	return page ? page_address(page) : NULL;
 
 
 
 
 211#endif
 212}
 213
 214static inline void free_thread_stack(struct task_struct *tsk)
 215{
 216#ifdef CONFIG_VMAP_STACK
 217	if (task_stack_vm_area(tsk)) {
 218		unsigned long flags;
 
 219		int i;
 220
 221		local_irq_save(flags);
 
 
 222		for (i = 0; i < NR_CACHED_STACKS; i++) {
 223			if (this_cpu_read(cached_stacks[i]))
 
 224				continue;
 225
 226			this_cpu_write(cached_stacks[i], tsk->stack_vm_area);
 227			local_irq_restore(flags);
 228			return;
 229		}
 230		local_irq_restore(flags);
 231
 232		vfree_atomic(tsk->stack);
 233		return;
 234	}
 235#endif
 236
 237	__free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
 238}
 239# else
 240static struct kmem_cache *thread_stack_cache;
 241
 242static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
 243						  int node)
 244{
 245	return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
 
 
 
 
 246}
 247
 248static void free_thread_stack(struct task_struct *tsk)
 249{
 250	kmem_cache_free(thread_stack_cache, tsk->stack);
 251}
 252
 253void thread_stack_cache_init(void)
 254{
 255	thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE,
 256					      THREAD_SIZE, 0, NULL);
 
 257	BUG_ON(thread_stack_cache == NULL);
 258}
 259# endif
 260#endif
 261
 262/* SLAB cache for signal_struct structures (tsk->signal) */
 263static struct kmem_cache *signal_cachep;
 264
 265/* SLAB cache for sighand_struct structures (tsk->sighand) */
 266struct kmem_cache *sighand_cachep;
 267
 268/* SLAB cache for files_struct structures (tsk->files) */
 269struct kmem_cache *files_cachep;
 270
 271/* SLAB cache for fs_struct structures (tsk->fs) */
 272struct kmem_cache *fs_cachep;
 273
 274/* SLAB cache for vm_area_struct structures */
 275struct kmem_cache *vm_area_cachep;
 276
 277/* SLAB cache for mm_struct structures (tsk->mm) */
 278static struct kmem_cache *mm_cachep;
 279
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 280static void account_kernel_stack(struct task_struct *tsk, int account)
 281{
 282	void *stack = task_stack_page(tsk);
 283	struct vm_struct *vm = task_stack_vm_area(tsk);
 284
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 285	BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
 286
 287	if (vm) {
 288		int i;
 289
 290		BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
 291
 292		for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
 293			mod_zone_page_state(page_zone(vm->pages[i]),
 294					    NR_KERNEL_STACK_KB,
 295					    PAGE_SIZE / 1024 * account);
 
 
 
 
 
 
 296		}
 297
 298		/* All stack pages belong to the same memcg. */
 299		memcg_kmem_update_page_stat(vm->pages[0], MEMCG_KERNEL_STACK_KB,
 300					    account * (THREAD_SIZE / 1024));
 301	} else {
 302		/*
 303		 * All stack pages are in the same zone and belong to the
 304		 * same memcg.
 305		 */
 306		struct page *first_page = virt_to_page(stack);
 307
 308		mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
 309				    THREAD_SIZE / 1024 * account);
 310
 311		memcg_kmem_update_page_stat(first_page, MEMCG_KERNEL_STACK_KB,
 312					    account * (THREAD_SIZE / 1024));
 313	}
 
 
 314}
 315
 316static void release_task_stack(struct task_struct *tsk)
 317{
 318	if (WARN_ON(tsk->state != TASK_DEAD))
 319		return;  /* Better to leak the stack than to free prematurely */
 320
 321	account_kernel_stack(tsk, -1);
 322	arch_release_thread_stack(tsk->stack);
 323	free_thread_stack(tsk);
 324	tsk->stack = NULL;
 325#ifdef CONFIG_VMAP_STACK
 326	tsk->stack_vm_area = NULL;
 327#endif
 328}
 329
 330#ifdef CONFIG_THREAD_INFO_IN_TASK
 331void put_task_stack(struct task_struct *tsk)
 332{
 333	if (atomic_dec_and_test(&tsk->stack_refcount))
 334		release_task_stack(tsk);
 335}
 336#endif
 337
 338void free_task(struct task_struct *tsk)
 339{
 
 
 340#ifndef CONFIG_THREAD_INFO_IN_TASK
 341	/*
 342	 * The task is finally done with both the stack and thread_info,
 343	 * so free both.
 344	 */
 345	release_task_stack(tsk);
 346#else
 347	/*
 348	 * If the task had a separate stack allocation, it should be gone
 349	 * by now.
 350	 */
 351	WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0);
 352#endif
 353	rt_mutex_debug_task_free(tsk);
 354	ftrace_graph_exit_task(tsk);
 355	put_seccomp_filter(tsk);
 356	arch_release_task_struct(tsk);
 357	if (tsk->flags & PF_KTHREAD)
 358		free_kthread_struct(tsk);
 359	free_task_struct(tsk);
 360}
 361EXPORT_SYMBOL(free_task);
 362
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 363static inline void free_signal_struct(struct signal_struct *sig)
 364{
 365	taskstats_tgid_free(sig);
 366	sched_autogroup_exit(sig);
 367	/*
 368	 * __mmdrop is not safe to call from softirq context on x86 due to
 369	 * pgd_dtor so postpone it to the async context
 370	 */
 371	if (sig->oom_mm)
 372		mmdrop_async(sig->oom_mm);
 373	kmem_cache_free(signal_cachep, sig);
 374}
 375
 376static inline void put_signal_struct(struct signal_struct *sig)
 377{
 378	if (atomic_dec_and_test(&sig->sigcnt))
 379		free_signal_struct(sig);
 380}
 381
 382void __put_task_struct(struct task_struct *tsk)
 383{
 384	WARN_ON(!tsk->exit_state);
 385	WARN_ON(atomic_read(&tsk->usage));
 386	WARN_ON(tsk == current);
 387
 388	cgroup_free(tsk);
 389	task_numa_free(tsk);
 390	security_task_free(tsk);
 391	exit_creds(tsk);
 392	delayacct_tsk_free(tsk);
 393	put_signal_struct(tsk->signal);
 394
 395	if (!profile_handoff_task(tsk))
 396		free_task(tsk);
 397}
 398EXPORT_SYMBOL_GPL(__put_task_struct);
 399
 400void __init __weak arch_task_cache_init(void) { }
 401
 402/*
 403 * set_max_threads
 404 */
 405static void set_max_threads(unsigned int max_threads_suggested)
 406{
 407	u64 threads;
 
 408
 409	/*
 410	 * The number of threads shall be limited such that the thread
 411	 * structures may only consume a small part of the available memory.
 412	 */
 413	if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
 414		threads = MAX_THREADS;
 415	else
 416		threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
 417				    (u64) THREAD_SIZE * 8UL);
 418
 419	if (threads > max_threads_suggested)
 420		threads = max_threads_suggested;
 421
 422	max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
 423}
 424
 425#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
 426/* Initialized by the architecture: */
 427int arch_task_struct_size __read_mostly;
 428#endif
 429
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 430void __init fork_init(void)
 431{
 432	int i;
 433#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 434#ifndef ARCH_MIN_TASKALIGN
 435#define ARCH_MIN_TASKALIGN	L1_CACHE_BYTES
 436#endif
 
 
 
 437	/* create a slab on which task_structs can be allocated */
 438	task_struct_cachep = kmem_cache_create("task_struct",
 439			arch_task_struct_size, ARCH_MIN_TASKALIGN,
 440			SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL);
 
 
 441#endif
 442
 443	/* do the arch specific task caches init */
 444	arch_task_cache_init();
 445
 446	set_max_threads(MAX_THREADS);
 447
 448	init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 449	init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 450	init_task.signal->rlim[RLIMIT_SIGPENDING] =
 451		init_task.signal->rlim[RLIMIT_NPROC];
 452
 453	for (i = 0; i < UCOUNT_COUNTS; i++) {
 454		init_user_ns.ucount_max[i] = max_threads/2;
 455	}
 
 
 
 
 
 
 
 
 
 
 456}
 457
 458int __weak arch_dup_task_struct(struct task_struct *dst,
 459					       struct task_struct *src)
 460{
 461	*dst = *src;
 462	return 0;
 463}
 464
 465void set_task_stack_end_magic(struct task_struct *tsk)
 466{
 467	unsigned long *stackend;
 468
 469	stackend = end_of_stack(tsk);
 470	*stackend = STACK_END_MAGIC;	/* for overflow detection */
 471}
 472
 473static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 474{
 475	struct task_struct *tsk;
 476	unsigned long *stack;
 477	struct vm_struct *stack_vm_area;
 478	int err;
 479
 480	if (node == NUMA_NO_NODE)
 481		node = tsk_fork_get_node(orig);
 482	tsk = alloc_task_struct_node(node);
 483	if (!tsk)
 484		return NULL;
 485
 486	stack = alloc_thread_stack_node(tsk, node);
 487	if (!stack)
 488		goto free_tsk;
 489
 
 
 
 490	stack_vm_area = task_stack_vm_area(tsk);
 491
 492	err = arch_dup_task_struct(tsk, orig);
 493
 494	/*
 495	 * arch_dup_task_struct() clobbers the stack-related fields.  Make
 496	 * sure they're properly initialized before using any stack-related
 497	 * functions again.
 498	 */
 499	tsk->stack = stack;
 500#ifdef CONFIG_VMAP_STACK
 501	tsk->stack_vm_area = stack_vm_area;
 502#endif
 503#ifdef CONFIG_THREAD_INFO_IN_TASK
 504	atomic_set(&tsk->stack_refcount, 1);
 505#endif
 506
 507	if (err)
 508		goto free_stack;
 509
 
 
 
 
 510#ifdef CONFIG_SECCOMP
 511	/*
 512	 * We must handle setting up seccomp filters once we're under
 513	 * the sighand lock in case orig has changed between now and
 514	 * then. Until then, filter must be NULL to avoid messing up
 515	 * the usage counts on the error path calling free_task.
 516	 */
 517	tsk->seccomp.filter = NULL;
 518#endif
 519
 520	setup_thread_stack(tsk, orig);
 521	clear_user_return_notifier(tsk);
 522	clear_tsk_need_resched(tsk);
 523	set_task_stack_end_magic(tsk);
 524
 525#ifdef CONFIG_CC_STACKPROTECTOR
 526	tsk->stack_canary = get_random_int();
 527#endif
 
 
 528
 529	/*
 530	 * One for us, one for whoever does the "release_task()" (usually
 531	 * parent)
 532	 */
 533	atomic_set(&tsk->usage, 2);
 
 
 534#ifdef CONFIG_BLK_DEV_IO_TRACE
 535	tsk->btrace_seq = 0;
 536#endif
 537	tsk->splice_pipe = NULL;
 538	tsk->task_frag.page = NULL;
 539	tsk->wake_q.next = NULL;
 540
 541	account_kernel_stack(tsk, 1);
 542
 543	kcov_task_init(tsk);
 544
 
 
 
 
 
 
 
 
 
 
 
 
 545	return tsk;
 546
 547free_stack:
 548	free_thread_stack(tsk);
 549free_tsk:
 550	free_task_struct(tsk);
 551	return NULL;
 552}
 553
 554#ifdef CONFIG_MMU
 555static __latent_entropy int dup_mmap(struct mm_struct *mm,
 556					struct mm_struct *oldmm)
 557{
 558	struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 559	struct rb_node **rb_link, *rb_parent;
 560	int retval;
 561	unsigned long charge;
 562
 563	uprobe_start_dup_mmap();
 564	if (down_write_killable(&oldmm->mmap_sem)) {
 565		retval = -EINTR;
 566		goto fail_uprobe_end;
 567	}
 568	flush_cache_dup_mm(oldmm);
 569	uprobe_dup_mmap(oldmm, mm);
 570	/*
 571	 * Not linked in yet - no deadlock potential:
 572	 */
 573	down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 574
 575	/* No ordering required: file already has been exposed. */
 576	RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
 577
 578	mm->total_vm = oldmm->total_vm;
 579	mm->data_vm = oldmm->data_vm;
 580	mm->exec_vm = oldmm->exec_vm;
 581	mm->stack_vm = oldmm->stack_vm;
 582
 583	rb_link = &mm->mm_rb.rb_node;
 584	rb_parent = NULL;
 585	pprev = &mm->mmap;
 586	retval = ksm_fork(mm, oldmm);
 587	if (retval)
 588		goto out;
 589	retval = khugepaged_fork(mm, oldmm);
 590	if (retval)
 591		goto out;
 592
 593	prev = NULL;
 594	for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 595		struct file *file;
 596
 597		if (mpnt->vm_flags & VM_DONTCOPY) {
 598			vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
 599			continue;
 600		}
 601		charge = 0;
 602		if (mpnt->vm_flags & VM_ACCOUNT) {
 603			unsigned long len = vma_pages(mpnt);
 604
 605			if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
 606				goto fail_nomem;
 607			charge = len;
 608		}
 609		tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 610		if (!tmp)
 611			goto fail_nomem;
 612		*tmp = *mpnt;
 613		INIT_LIST_HEAD(&tmp->anon_vma_chain);
 614		retval = vma_dup_policy(mpnt, tmp);
 615		if (retval)
 616			goto fail_nomem_policy;
 617		tmp->vm_mm = mm;
 618		if (anon_vma_fork(tmp, mpnt))
 619			goto fail_nomem_anon_vma_fork;
 620		tmp->vm_flags &=
 621			~(VM_LOCKED|VM_LOCKONFAULT|VM_UFFD_MISSING|VM_UFFD_WP);
 622		tmp->vm_next = tmp->vm_prev = NULL;
 623		tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
 624		file = tmp->vm_file;
 625		if (file) {
 626			struct inode *inode = file_inode(file);
 627			struct address_space *mapping = file->f_mapping;
 628
 629			get_file(file);
 630			if (tmp->vm_flags & VM_DENYWRITE)
 631				atomic_dec(&inode->i_writecount);
 632			i_mmap_lock_write(mapping);
 633			if (tmp->vm_flags & VM_SHARED)
 634				atomic_inc(&mapping->i_mmap_writable);
 635			flush_dcache_mmap_lock(mapping);
 636			/* insert tmp into the share list, just after mpnt */
 637			vma_interval_tree_insert_after(tmp, mpnt,
 638					&mapping->i_mmap);
 639			flush_dcache_mmap_unlock(mapping);
 640			i_mmap_unlock_write(mapping);
 641		}
 642
 643		/*
 644		 * Clear hugetlb-related page reserves for children. This only
 645		 * affects MAP_PRIVATE mappings. Faults generated by the child
 646		 * are not guaranteed to succeed, even if read-only
 647		 */
 648		if (is_vm_hugetlb_page(tmp))
 649			reset_vma_resv_huge_pages(tmp);
 650
 651		/*
 652		 * Link in the new vma and copy the page table entries.
 653		 */
 654		*pprev = tmp;
 655		pprev = &tmp->vm_next;
 656		tmp->vm_prev = prev;
 657		prev = tmp;
 658
 659		__vma_link_rb(mm, tmp, rb_link, rb_parent);
 660		rb_link = &tmp->vm_rb.rb_right;
 661		rb_parent = &tmp->vm_rb;
 662
 663		mm->map_count++;
 664		retval = copy_page_range(mm, oldmm, mpnt);
 665
 666		if (tmp->vm_ops && tmp->vm_ops->open)
 667			tmp->vm_ops->open(tmp);
 668
 669		if (retval)
 670			goto out;
 671	}
 672	/* a new mm has just been created */
 673	arch_dup_mmap(oldmm, mm);
 674	retval = 0;
 675out:
 676	up_write(&mm->mmap_sem);
 677	flush_tlb_mm(oldmm);
 678	up_write(&oldmm->mmap_sem);
 679fail_uprobe_end:
 680	uprobe_end_dup_mmap();
 681	return retval;
 682fail_nomem_anon_vma_fork:
 683	mpol_put(vma_policy(tmp));
 684fail_nomem_policy:
 685	kmem_cache_free(vm_area_cachep, tmp);
 686fail_nomem:
 687	retval = -ENOMEM;
 688	vm_unacct_memory(charge);
 689	goto out;
 690}
 691
 692static inline int mm_alloc_pgd(struct mm_struct *mm)
 693{
 694	mm->pgd = pgd_alloc(mm);
 695	if (unlikely(!mm->pgd))
 696		return -ENOMEM;
 697	return 0;
 698}
 699
 700static inline void mm_free_pgd(struct mm_struct *mm)
 701{
 702	pgd_free(mm, mm->pgd);
 703}
 704#else
 705static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 706{
 707	down_write(&oldmm->mmap_sem);
 708	RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
 709	up_write(&oldmm->mmap_sem);
 710	return 0;
 711}
 712#define mm_alloc_pgd(mm)	(0)
 713#define mm_free_pgd(mm)
 714#endif /* CONFIG_MMU */
 715
 716__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 717
 718#define allocate_mm()	(kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 719#define free_mm(mm)	(kmem_cache_free(mm_cachep, (mm)))
 720
 721static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 722
 723static int __init coredump_filter_setup(char *s)
 724{
 725	default_dump_filter =
 726		(simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 727		MMF_DUMP_FILTER_MASK;
 728	return 1;
 729}
 730
 731__setup("coredump_filter=", coredump_filter_setup);
 732
 733#include <linux/init_task.h>
 734
 735static void mm_init_aio(struct mm_struct *mm)
 736{
 737#ifdef CONFIG_AIO
 738	spin_lock_init(&mm->ioctx_lock);
 739	mm->ioctx_table = NULL;
 740#endif
 741}
 742
 
 
 
 
 
 
 
 
 
 743static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 744{
 745#ifdef CONFIG_MEMCG
 746	mm->owner = p;
 747#endif
 748}
 749
 
 
 
 
 
 
 
 750static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
 751	struct user_namespace *user_ns)
 752{
 753	mm->mmap = NULL;
 754	mm->mm_rb = RB_ROOT;
 755	mm->vmacache_seqnum = 0;
 756	atomic_set(&mm->mm_users, 1);
 757	atomic_set(&mm->mm_count, 1);
 758	init_rwsem(&mm->mmap_sem);
 759	INIT_LIST_HEAD(&mm->mmlist);
 760	mm->core_state = NULL;
 761	atomic_long_set(&mm->nr_ptes, 0);
 762	mm_nr_pmds_init(mm);
 763	mm->map_count = 0;
 764	mm->locked_vm = 0;
 765	mm->pinned_vm = 0;
 
 766	memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 767	spin_lock_init(&mm->page_table_lock);
 
 768	mm_init_cpumask(mm);
 769	mm_init_aio(mm);
 770	mm_init_owner(mm, p);
 771	mmu_notifier_mm_init(mm);
 772	clear_tlb_flush_pending(mm);
 
 773#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 774	mm->pmd_huge_pte = NULL;
 775#endif
 
 776
 777	if (current->mm) {
 778		mm->flags = current->mm->flags & MMF_INIT_MASK;
 779		mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
 780	} else {
 781		mm->flags = default_dump_filter;
 782		mm->def_flags = 0;
 783	}
 784
 785	if (mm_alloc_pgd(mm))
 786		goto fail_nopgd;
 787
 788	if (init_new_context(p, mm))
 789		goto fail_nocontext;
 790
 791	mm->user_ns = get_user_ns(user_ns);
 792	return mm;
 793
 794fail_nocontext:
 795	mm_free_pgd(mm);
 796fail_nopgd:
 797	free_mm(mm);
 798	return NULL;
 799}
 800
 801static void check_mm(struct mm_struct *mm)
 802{
 803	int i;
 804
 805	for (i = 0; i < NR_MM_COUNTERS; i++) {
 806		long x = atomic_long_read(&mm->rss_stat.count[i]);
 807
 808		if (unlikely(x))
 809			printk(KERN_ALERT "BUG: Bad rss-counter state "
 810					  "mm:%p idx:%d val:%ld\n", mm, i, x);
 811	}
 812
 813	if (atomic_long_read(&mm->nr_ptes))
 814		pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
 815				atomic_long_read(&mm->nr_ptes));
 816	if (mm_nr_pmds(mm))
 817		pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
 818				mm_nr_pmds(mm));
 819
 820#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 821	VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
 822#endif
 823}
 824
 825/*
 826 * Allocate and initialize an mm_struct.
 827 */
 828struct mm_struct *mm_alloc(void)
 829{
 830	struct mm_struct *mm;
 831
 832	mm = allocate_mm();
 833	if (!mm)
 834		return NULL;
 835
 836	memset(mm, 0, sizeof(*mm));
 837	return mm_init(mm, current, current_user_ns());
 838}
 839
 840/*
 841 * Called when the last reference to the mm
 842 * is dropped: either by a lazy thread or by
 843 * mmput. Free the page directory and the mm.
 844 */
 845void __mmdrop(struct mm_struct *mm)
 846{
 847	BUG_ON(mm == &init_mm);
 848	mm_free_pgd(mm);
 849	destroy_context(mm);
 850	mmu_notifier_mm_destroy(mm);
 851	check_mm(mm);
 852	put_user_ns(mm->user_ns);
 853	free_mm(mm);
 854}
 855EXPORT_SYMBOL_GPL(__mmdrop);
 856
 857static inline void __mmput(struct mm_struct *mm)
 858{
 859	VM_BUG_ON(atomic_read(&mm->mm_users));
 860
 861	uprobe_clear_state(mm);
 862	exit_aio(mm);
 863	ksm_exit(mm);
 864	khugepaged_exit(mm); /* must run before exit_mmap */
 865	exit_mmap(mm);
 866	mm_put_huge_zero_page(mm);
 867	set_mm_exe_file(mm, NULL);
 868	if (!list_empty(&mm->mmlist)) {
 869		spin_lock(&mmlist_lock);
 870		list_del(&mm->mmlist);
 871		spin_unlock(&mmlist_lock);
 872	}
 873	if (mm->binfmt)
 874		module_put(mm->binfmt->module);
 875	set_bit(MMF_OOM_SKIP, &mm->flags);
 876	mmdrop(mm);
 877}
 878
 879/*
 880 * Decrement the use count and release all resources for an mm.
 881 */
 882void mmput(struct mm_struct *mm)
 883{
 884	might_sleep();
 885
 886	if (atomic_dec_and_test(&mm->mm_users))
 887		__mmput(mm);
 888}
 889EXPORT_SYMBOL_GPL(mmput);
 890
 891#ifdef CONFIG_MMU
 892static void mmput_async_fn(struct work_struct *work)
 893{
 894	struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work);
 
 
 895	__mmput(mm);
 896}
 897
 898void mmput_async(struct mm_struct *mm)
 899{
 900	if (atomic_dec_and_test(&mm->mm_users)) {
 901		INIT_WORK(&mm->async_put_work, mmput_async_fn);
 902		schedule_work(&mm->async_put_work);
 903	}
 904}
 905#endif
 906
 907/**
 908 * set_mm_exe_file - change a reference to the mm's executable file
 909 *
 910 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
 911 *
 912 * Main users are mmput() and sys_execve(). Callers prevent concurrent
 913 * invocations: in mmput() nobody alive left, in execve task is single
 914 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
 915 * mm->exe_file, but does so without using set_mm_exe_file() in order
 916 * to do avoid the need for any locks.
 917 */
 918void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 919{
 920	struct file *old_exe_file;
 921
 922	/*
 923	 * It is safe to dereference the exe_file without RCU as
 924	 * this function is only called if nobody else can access
 925	 * this mm -- see comment above for justification.
 926	 */
 927	old_exe_file = rcu_dereference_raw(mm->exe_file);
 928
 929	if (new_exe_file)
 930		get_file(new_exe_file);
 931	rcu_assign_pointer(mm->exe_file, new_exe_file);
 932	if (old_exe_file)
 933		fput(old_exe_file);
 934}
 935
 936/**
 937 * get_mm_exe_file - acquire a reference to the mm's executable file
 938 *
 939 * Returns %NULL if mm has no associated executable file.
 940 * User must release file via fput().
 941 */
 942struct file *get_mm_exe_file(struct mm_struct *mm)
 943{
 944	struct file *exe_file;
 945
 946	rcu_read_lock();
 947	exe_file = rcu_dereference(mm->exe_file);
 948	if (exe_file && !get_file_rcu(exe_file))
 949		exe_file = NULL;
 950	rcu_read_unlock();
 951	return exe_file;
 952}
 953EXPORT_SYMBOL(get_mm_exe_file);
 954
 955/**
 956 * get_task_exe_file - acquire a reference to the task's executable file
 957 *
 958 * Returns %NULL if task's mm (if any) has no associated executable file or
 959 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
 960 * User must release file via fput().
 961 */
 962struct file *get_task_exe_file(struct task_struct *task)
 963{
 964	struct file *exe_file = NULL;
 965	struct mm_struct *mm;
 966
 967	task_lock(task);
 968	mm = task->mm;
 969	if (mm) {
 970		if (!(task->flags & PF_KTHREAD))
 971			exe_file = get_mm_exe_file(mm);
 972	}
 973	task_unlock(task);
 974	return exe_file;
 975}
 976EXPORT_SYMBOL(get_task_exe_file);
 977
 978/**
 979 * get_task_mm - acquire a reference to the task's mm
 980 *
 981 * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 982 * this kernel workthread has transiently adopted a user mm with use_mm,
 983 * to do its AIO) is not set and if so returns a reference to it, after
 984 * bumping up the use count.  User must release the mm via mmput()
 985 * after use.  Typically used by /proc and ptrace.
 986 */
 987struct mm_struct *get_task_mm(struct task_struct *task)
 988{
 989	struct mm_struct *mm;
 990
 991	task_lock(task);
 992	mm = task->mm;
 993	if (mm) {
 994		if (task->flags & PF_KTHREAD)
 995			mm = NULL;
 996		else
 997			atomic_inc(&mm->mm_users);
 998	}
 999	task_unlock(task);
1000	return mm;
1001}
1002EXPORT_SYMBOL_GPL(get_task_mm);
1003
1004struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1005{
1006	struct mm_struct *mm;
1007	int err;
1008
1009	err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
1010	if (err)
1011		return ERR_PTR(err);
1012
1013	mm = get_task_mm(task);
1014	if (mm && mm != current->mm &&
1015			!ptrace_may_access(task, mode)) {
1016		mmput(mm);
1017		mm = ERR_PTR(-EACCES);
1018	}
1019	mutex_unlock(&task->signal->cred_guard_mutex);
1020
1021	return mm;
1022}
1023
1024static void complete_vfork_done(struct task_struct *tsk)
1025{
1026	struct completion *vfork;
1027
1028	task_lock(tsk);
1029	vfork = tsk->vfork_done;
1030	if (likely(vfork)) {
1031		tsk->vfork_done = NULL;
1032		complete(vfork);
1033	}
1034	task_unlock(tsk);
1035}
1036
1037static int wait_for_vfork_done(struct task_struct *child,
1038				struct completion *vfork)
1039{
1040	int killed;
1041
1042	freezer_do_not_count();
 
1043	killed = wait_for_completion_killable(vfork);
 
1044	freezer_count();
1045
1046	if (killed) {
1047		task_lock(child);
1048		child->vfork_done = NULL;
1049		task_unlock(child);
1050	}
1051
1052	put_task_struct(child);
1053	return killed;
1054}
1055
1056/* Please note the differences between mmput and mm_release.
1057 * mmput is called whenever we stop holding onto a mm_struct,
1058 * error success whatever.
1059 *
1060 * mm_release is called after a mm_struct has been removed
1061 * from the current process.
1062 *
1063 * This difference is important for error handling, when we
1064 * only half set up a mm_struct for a new process and need to restore
1065 * the old one.  Because we mmput the new mm_struct before
1066 * restoring the old one. . .
1067 * Eric Biederman 10 January 1998
1068 */
1069void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1070{
1071	/* Get rid of any futexes when releasing the mm */
1072#ifdef CONFIG_FUTEX
1073	if (unlikely(tsk->robust_list)) {
1074		exit_robust_list(tsk);
1075		tsk->robust_list = NULL;
1076	}
1077#ifdef CONFIG_COMPAT
1078	if (unlikely(tsk->compat_robust_list)) {
1079		compat_exit_robust_list(tsk);
1080		tsk->compat_robust_list = NULL;
1081	}
1082#endif
1083	if (unlikely(!list_empty(&tsk->pi_state_list)))
1084		exit_pi_state_list(tsk);
1085#endif
1086
1087	uprobe_free_utask(tsk);
1088
1089	/* Get rid of any cached register state */
1090	deactivate_mm(tsk, mm);
1091
1092	/*
1093	 * Signal userspace if we're not exiting with a core dump
1094	 * because we want to leave the value intact for debugging
1095	 * purposes.
1096	 */
1097	if (tsk->clear_child_tid) {
1098		if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1099		    atomic_read(&mm->mm_users) > 1) {
1100			/*
1101			 * We don't check the error code - if userspace has
1102			 * not set up a proper pointer then tough luck.
1103			 */
1104			put_user(0, tsk->clear_child_tid);
1105			sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
1106					1, NULL, NULL, 0);
1107		}
1108		tsk->clear_child_tid = NULL;
1109	}
1110
1111	/*
1112	 * All done, finally we can wake up parent and return this mm to him.
1113	 * Also kthread_stop() uses this completion for synchronization.
1114	 */
1115	if (tsk->vfork_done)
1116		complete_vfork_done(tsk);
1117}
1118
1119/*
1120 * Allocate a new mm structure and copy contents from the
1121 * mm structure of the passed in task structure.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1122 */
1123static struct mm_struct *dup_mm(struct task_struct *tsk)
 
1124{
1125	struct mm_struct *mm, *oldmm = current->mm;
1126	int err;
1127
1128	mm = allocate_mm();
1129	if (!mm)
1130		goto fail_nomem;
1131
1132	memcpy(mm, oldmm, sizeof(*mm));
1133
1134	if (!mm_init(mm, tsk, mm->user_ns))
1135		goto fail_nomem;
1136
1137	err = dup_mmap(mm, oldmm);
1138	if (err)
1139		goto free_pt;
1140
1141	mm->hiwater_rss = get_mm_rss(mm);
1142	mm->hiwater_vm = mm->total_vm;
1143
1144	if (mm->binfmt && !try_module_get(mm->binfmt->module))
1145		goto free_pt;
1146
1147	return mm;
1148
1149free_pt:
1150	/* don't put binfmt in mmput, we haven't got module yet */
1151	mm->binfmt = NULL;
 
1152	mmput(mm);
1153
1154fail_nomem:
1155	return NULL;
1156}
1157
1158static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1159{
1160	struct mm_struct *mm, *oldmm;
1161	int retval;
1162
1163	tsk->min_flt = tsk->maj_flt = 0;
1164	tsk->nvcsw = tsk->nivcsw = 0;
1165#ifdef CONFIG_DETECT_HUNG_TASK
1166	tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 
1167#endif
1168
1169	tsk->mm = NULL;
1170	tsk->active_mm = NULL;
1171
1172	/*
1173	 * Are we cloning a kernel thread?
1174	 *
1175	 * We need to steal a active VM for that..
1176	 */
1177	oldmm = current->mm;
1178	if (!oldmm)
1179		return 0;
1180
1181	/* initialize the new vmacache entries */
1182	vmacache_flush(tsk);
1183
1184	if (clone_flags & CLONE_VM) {
1185		atomic_inc(&oldmm->mm_users);
1186		mm = oldmm;
1187		goto good_mm;
1188	}
1189
1190	retval = -ENOMEM;
1191	mm = dup_mm(tsk);
1192	if (!mm)
1193		goto fail_nomem;
1194
1195good_mm:
1196	tsk->mm = mm;
1197	tsk->active_mm = mm;
1198	return 0;
1199
1200fail_nomem:
1201	return retval;
1202}
1203
1204static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1205{
1206	struct fs_struct *fs = current->fs;
1207	if (clone_flags & CLONE_FS) {
1208		/* tsk->fs is already what we want */
1209		spin_lock(&fs->lock);
1210		if (fs->in_exec) {
1211			spin_unlock(&fs->lock);
1212			return -EAGAIN;
1213		}
1214		fs->users++;
1215		spin_unlock(&fs->lock);
1216		return 0;
1217	}
1218	tsk->fs = copy_fs_struct(fs);
1219	if (!tsk->fs)
1220		return -ENOMEM;
1221	return 0;
1222}
1223
1224static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1225{
1226	struct files_struct *oldf, *newf;
1227	int error = 0;
1228
1229	/*
1230	 * A background process may not have any files ...
1231	 */
1232	oldf = current->files;
1233	if (!oldf)
1234		goto out;
1235
1236	if (clone_flags & CLONE_FILES) {
1237		atomic_inc(&oldf->count);
1238		goto out;
1239	}
1240
1241	newf = dup_fd(oldf, &error);
1242	if (!newf)
1243		goto out;
1244
1245	tsk->files = newf;
1246	error = 0;
1247out:
1248	return error;
1249}
1250
1251static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1252{
1253#ifdef CONFIG_BLOCK
1254	struct io_context *ioc = current->io_context;
1255	struct io_context *new_ioc;
1256
1257	if (!ioc)
1258		return 0;
1259	/*
1260	 * Share io context with parent, if CLONE_IO is set
1261	 */
1262	if (clone_flags & CLONE_IO) {
1263		ioc_task_link(ioc);
1264		tsk->io_context = ioc;
1265	} else if (ioprio_valid(ioc->ioprio)) {
1266		new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1267		if (unlikely(!new_ioc))
1268			return -ENOMEM;
1269
1270		new_ioc->ioprio = ioc->ioprio;
1271		put_io_context(new_ioc);
1272	}
1273#endif
1274	return 0;
1275}
1276
1277static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1278{
1279	struct sighand_struct *sig;
1280
1281	if (clone_flags & CLONE_SIGHAND) {
1282		atomic_inc(&current->sighand->count);
1283		return 0;
1284	}
1285	sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1286	rcu_assign_pointer(tsk->sighand, sig);
1287	if (!sig)
1288		return -ENOMEM;
1289
1290	atomic_set(&sig->count, 1);
 
1291	memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 
 
 
 
 
 
1292	return 0;
1293}
1294
1295void __cleanup_sighand(struct sighand_struct *sighand)
1296{
1297	if (atomic_dec_and_test(&sighand->count)) {
1298		signalfd_cleanup(sighand);
1299		/*
1300		 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
1301		 * without an RCU grace period, see __lock_task_sighand().
1302		 */
1303		kmem_cache_free(sighand_cachep, sighand);
1304	}
1305}
1306
1307/*
1308 * Initialize POSIX timer handling for a thread group.
1309 */
1310static void posix_cpu_timers_init_group(struct signal_struct *sig)
1311{
 
1312	unsigned long cpu_limit;
1313
1314	cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1315	if (cpu_limit != RLIM_INFINITY) {
1316		sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1317		sig->cputimer.running = true;
1318	}
1319
1320	/* The timer lists. */
1321	INIT_LIST_HEAD(&sig->cpu_timers[0]);
1322	INIT_LIST_HEAD(&sig->cpu_timers[1]);
1323	INIT_LIST_HEAD(&sig->cpu_timers[2]);
1324}
1325
1326static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1327{
1328	struct signal_struct *sig;
1329
1330	if (clone_flags & CLONE_THREAD)
1331		return 0;
1332
1333	sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1334	tsk->signal = sig;
1335	if (!sig)
1336		return -ENOMEM;
1337
1338	sig->nr_threads = 1;
1339	atomic_set(&sig->live, 1);
1340	atomic_set(&sig->sigcnt, 1);
1341
1342	/* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1343	sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1344	tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1345
1346	init_waitqueue_head(&sig->wait_chldexit);
1347	sig->curr_target = tsk;
1348	init_sigpending(&sig->shared_pending);
1349	INIT_LIST_HEAD(&sig->posix_timers);
1350	seqlock_init(&sig->stats_lock);
1351	prev_cputime_init(&sig->prev_cputime);
1352
1353#ifdef CONFIG_POSIX_TIMERS
 
1354	hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1355	sig->real_timer.function = it_real_fn;
1356#endif
1357
1358	task_lock(current->group_leader);
1359	memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1360	task_unlock(current->group_leader);
1361
1362	posix_cpu_timers_init_group(sig);
1363
1364	tty_audit_fork(sig);
1365	sched_autogroup_fork(sig);
1366
1367	sig->oom_score_adj = current->signal->oom_score_adj;
1368	sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1369
1370	sig->has_child_subreaper = current->signal->has_child_subreaper ||
1371				   current->signal->is_child_subreaper;
1372
1373	mutex_init(&sig->cred_guard_mutex);
 
1374
1375	return 0;
1376}
1377
1378static void copy_seccomp(struct task_struct *p)
1379{
1380#ifdef CONFIG_SECCOMP
1381	/*
1382	 * Must be called with sighand->lock held, which is common to
1383	 * all threads in the group. Holding cred_guard_mutex is not
1384	 * needed because this new task is not yet running and cannot
1385	 * be racing exec.
1386	 */
1387	assert_spin_locked(&current->sighand->siglock);
1388
1389	/* Ref-count the new filter user, and assign it. */
1390	get_seccomp_filter(current);
1391	p->seccomp = current->seccomp;
1392
1393	/*
1394	 * Explicitly enable no_new_privs here in case it got set
1395	 * between the task_struct being duplicated and holding the
1396	 * sighand lock. The seccomp state and nnp must be in sync.
1397	 */
1398	if (task_no_new_privs(current))
1399		task_set_no_new_privs(p);
1400
1401	/*
1402	 * If the parent gained a seccomp mode after copying thread
1403	 * flags and between before we held the sighand lock, we have
1404	 * to manually enable the seccomp thread flag here.
1405	 */
1406	if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1407		set_tsk_thread_flag(p, TIF_SECCOMP);
1408#endif
1409}
1410
1411SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1412{
1413	current->clear_child_tid = tidptr;
1414
1415	return task_pid_vnr(current);
1416}
1417
1418static void rt_mutex_init_task(struct task_struct *p)
1419{
1420	raw_spin_lock_init(&p->pi_lock);
1421#ifdef CONFIG_RT_MUTEXES
1422	p->pi_waiters = RB_ROOT;
1423	p->pi_waiters_leftmost = NULL;
1424	p->pi_blocked_on = NULL;
1425#endif
1426}
1427
1428/*
1429 * Initialize POSIX timer handling for a single task.
1430 */
1431static void posix_cpu_timers_init(struct task_struct *tsk)
1432{
1433	tsk->cputime_expires.prof_exp = 0;
1434	tsk->cputime_expires.virt_exp = 0;
1435	tsk->cputime_expires.sched_exp = 0;
1436	INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1437	INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1438	INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1439}
1440
1441static inline void
1442init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1443{
1444	 task->pids[type].pid = pid;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1445}
1446
1447/*
1448 * This creates a new process as a copy of the old one,
1449 * but does not actually start it yet.
1450 *
1451 * It copies the registers, and all the appropriate
1452 * parts of the process environment (as per the clone
1453 * flags). The actual kick-off is left to the caller.
1454 */
1455static __latent_entropy struct task_struct *copy_process(
1456					unsigned long clone_flags,
1457					unsigned long stack_start,
1458					unsigned long stack_size,
1459					int __user *child_tidptr,
1460					struct pid *pid,
1461					int trace,
1462					unsigned long tls,
1463					int node)
1464{
1465	int retval;
1466	struct task_struct *p;
 
 
 
 
1467
 
 
 
 
1468	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1469		return ERR_PTR(-EINVAL);
1470
1471	if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1472		return ERR_PTR(-EINVAL);
1473
1474	/*
1475	 * Thread groups must share signals as well, and detached threads
1476	 * can only be started up within the thread group.
1477	 */
1478	if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1479		return ERR_PTR(-EINVAL);
1480
1481	/*
1482	 * Shared signal handlers imply shared VM. By way of the above,
1483	 * thread groups also imply shared VM. Blocking this case allows
1484	 * for various simplifications in other code.
1485	 */
1486	if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1487		return ERR_PTR(-EINVAL);
1488
1489	/*
1490	 * Siblings of global init remain as zombies on exit since they are
1491	 * not reaped by their parent (swapper). To solve this and to avoid
1492	 * multi-rooted process trees, prevent global and container-inits
1493	 * from creating siblings.
1494	 */
1495	if ((clone_flags & CLONE_PARENT) &&
1496				current->signal->flags & SIGNAL_UNKILLABLE)
1497		return ERR_PTR(-EINVAL);
1498
1499	/*
1500	 * If the new process will be in a different pid or user namespace
1501	 * do not allow it to share a thread group with the forking task.
1502	 */
1503	if (clone_flags & CLONE_THREAD) {
1504		if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1505		    (task_active_pid_ns(current) !=
1506				current->nsproxy->pid_ns_for_children))
1507			return ERR_PTR(-EINVAL);
1508	}
1509
1510	retval = security_task_create(clone_flags);
1511	if (retval)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1512		goto fork_out;
1513
1514	retval = -ENOMEM;
1515	p = dup_task_struct(current, node);
1516	if (!p)
1517		goto fork_out;
1518
 
 
 
 
 
 
 
 
 
 
 
 
1519	ftrace_graph_init_task(p);
1520
1521	rt_mutex_init_task(p);
1522
 
1523#ifdef CONFIG_PROVE_LOCKING
1524	DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1525	DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1526#endif
1527	retval = -EAGAIN;
1528	if (atomic_read(&p->real_cred->user->processes) >=
1529			task_rlimit(p, RLIMIT_NPROC)) {
1530		if (p->real_cred->user != INIT_USER &&
1531		    !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1532			goto bad_fork_free;
1533	}
1534	current->flags &= ~PF_NPROC_EXCEEDED;
1535
1536	retval = copy_creds(p, clone_flags);
1537	if (retval < 0)
1538		goto bad_fork_free;
1539
1540	/*
1541	 * If multiple threads are within copy_process(), then this check
1542	 * triggers too late. This doesn't hurt, the check is only there
1543	 * to stop root fork bombs.
1544	 */
1545	retval = -EAGAIN;
1546	if (nr_threads >= max_threads)
1547		goto bad_fork_cleanup_count;
1548
1549	delayacct_tsk_init(p);	/* Must remain after dup_task_struct() */
1550	p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1551	p->flags |= PF_FORKNOEXEC;
1552	INIT_LIST_HEAD(&p->children);
1553	INIT_LIST_HEAD(&p->sibling);
1554	rcu_copy_process(p);
1555	p->vfork_done = NULL;
1556	spin_lock_init(&p->alloc_lock);
1557
1558	init_sigpending(&p->pending);
1559
1560	p->utime = p->stime = p->gtime = 0;
1561#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1562	p->utimescaled = p->stimescaled = 0;
1563#endif
1564	prev_cputime_init(&p->prev_cputime);
1565
1566#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1567	seqcount_init(&p->vtime_seqcount);
1568	p->vtime_snap = 0;
1569	p->vtime_snap_whence = VTIME_INACTIVE;
1570#endif
1571
1572#if defined(SPLIT_RSS_COUNTING)
1573	memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1574#endif
1575
1576	p->default_timer_slack_ns = current->timer_slack_ns;
1577
 
 
 
 
1578	task_io_accounting_init(&p->ioac);
1579	acct_clear_integrals(p);
1580
1581	posix_cpu_timers_init(p);
1582
1583	p->start_time = ktime_get_ns();
1584	p->real_start_time = ktime_get_boot_ns();
1585	p->io_context = NULL;
1586	p->audit_context = NULL;
1587	cgroup_fork(p);
1588#ifdef CONFIG_NUMA
1589	p->mempolicy = mpol_dup(p->mempolicy);
1590	if (IS_ERR(p->mempolicy)) {
1591		retval = PTR_ERR(p->mempolicy);
1592		p->mempolicy = NULL;
1593		goto bad_fork_cleanup_threadgroup_lock;
1594	}
1595#endif
1596#ifdef CONFIG_CPUSETS
1597	p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1598	p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1599	seqcount_init(&p->mems_allowed_seq);
1600#endif
1601#ifdef CONFIG_TRACE_IRQFLAGS
1602	p->irq_events = 0;
1603	p->hardirqs_enabled = 0;
1604	p->hardirq_enable_ip = 0;
1605	p->hardirq_enable_event = 0;
1606	p->hardirq_disable_ip = _THIS_IP_;
1607	p->hardirq_disable_event = 0;
1608	p->softirqs_enabled = 1;
1609	p->softirq_enable_ip = _THIS_IP_;
1610	p->softirq_enable_event = 0;
1611	p->softirq_disable_ip = 0;
1612	p->softirq_disable_event = 0;
1613	p->hardirq_context = 0;
1614	p->softirq_context = 0;
1615#endif
1616
1617	p->pagefault_disabled = 0;
1618
1619#ifdef CONFIG_LOCKDEP
1620	p->lockdep_depth = 0; /* no locks held yet */
1621	p->curr_chain_key = 0;
1622	p->lockdep_recursion = 0;
1623#endif
1624
1625#ifdef CONFIG_DEBUG_MUTEXES
1626	p->blocked_on = NULL; /* not blocked yet */
1627#endif
1628#ifdef CONFIG_BCACHE
1629	p->sequential_io	= 0;
1630	p->sequential_io_avg	= 0;
1631#endif
1632
1633	/* Perform scheduler related setup. Assign this task to a CPU. */
1634	retval = sched_fork(clone_flags, p);
1635	if (retval)
1636		goto bad_fork_cleanup_policy;
1637
1638	retval = perf_event_init_task(p);
1639	if (retval)
1640		goto bad_fork_cleanup_policy;
1641	retval = audit_alloc(p);
1642	if (retval)
1643		goto bad_fork_cleanup_perf;
1644	/* copy all the process information */
1645	shm_init_task(p);
1646	retval = copy_semundo(clone_flags, p);
1647	if (retval)
1648		goto bad_fork_cleanup_audit;
 
 
 
1649	retval = copy_files(clone_flags, p);
1650	if (retval)
1651		goto bad_fork_cleanup_semundo;
1652	retval = copy_fs(clone_flags, p);
1653	if (retval)
1654		goto bad_fork_cleanup_files;
1655	retval = copy_sighand(clone_flags, p);
1656	if (retval)
1657		goto bad_fork_cleanup_fs;
1658	retval = copy_signal(clone_flags, p);
1659	if (retval)
1660		goto bad_fork_cleanup_sighand;
1661	retval = copy_mm(clone_flags, p);
1662	if (retval)
1663		goto bad_fork_cleanup_signal;
1664	retval = copy_namespaces(clone_flags, p);
1665	if (retval)
1666		goto bad_fork_cleanup_mm;
1667	retval = copy_io(clone_flags, p);
1668	if (retval)
1669		goto bad_fork_cleanup_namespaces;
1670	retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1671	if (retval)
1672		goto bad_fork_cleanup_io;
1673
 
 
1674	if (pid != &init_struct_pid) {
1675		pid = alloc_pid(p->nsproxy->pid_ns_for_children);
 
1676		if (IS_ERR(pid)) {
1677			retval = PTR_ERR(pid);
1678			goto bad_fork_cleanup_thread;
1679		}
1680	}
1681
1682	p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1683	/*
1684	 * Clear TID on mm_release()?
1685	 */
1686	p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1687#ifdef CONFIG_BLOCK
1688	p->plug = NULL;
1689#endif
1690#ifdef CONFIG_FUTEX
1691	p->robust_list = NULL;
1692#ifdef CONFIG_COMPAT
1693	p->compat_robust_list = NULL;
1694#endif
1695	INIT_LIST_HEAD(&p->pi_state_list);
1696	p->pi_state_cache = NULL;
1697#endif
1698	/*
1699	 * sigaltstack should be cleared when sharing the same VM
1700	 */
1701	if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1702		sas_ss_reset(p);
1703
1704	/*
1705	 * Syscall tracing and stepping should be turned off in the
1706	 * child regardless of CLONE_PTRACE.
1707	 */
1708	user_disable_single_step(p);
1709	clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1710#ifdef TIF_SYSCALL_EMU
1711	clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1712#endif
1713	clear_all_latency_tracing(p);
1714
1715	/* ok, now we should be set up.. */
1716	p->pid = pid_nr(pid);
1717	if (clone_flags & CLONE_THREAD) {
1718		p->exit_signal = -1;
1719		p->group_leader = current->group_leader;
1720		p->tgid = current->tgid;
1721	} else {
1722		if (clone_flags & CLONE_PARENT)
1723			p->exit_signal = current->group_leader->exit_signal;
1724		else
1725			p->exit_signal = (clone_flags & CSIGNAL);
1726		p->group_leader = p;
1727		p->tgid = p->pid;
1728	}
1729
1730	p->nr_dirtied = 0;
1731	p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1732	p->dirty_paused_when = 0;
1733
1734	p->pdeath_signal = 0;
1735	INIT_LIST_HEAD(&p->thread_group);
1736	p->task_works = NULL;
1737
1738	threadgroup_change_begin(current);
1739	/*
1740	 * Ensure that the cgroup subsystem policies allow the new process to be
1741	 * forked. It should be noted the the new process's css_set can be changed
1742	 * between here and cgroup_post_fork() if an organisation operation is in
1743	 * progress.
1744	 */
1745	retval = cgroup_can_fork(p);
1746	if (retval)
1747		goto bad_fork_free_pid;
 
 
 
 
 
 
 
 
 
 
 
1748
1749	/*
1750	 * Make it visible to the rest of the system, but dont wake it up yet.
1751	 * Need tasklist lock for parent etc handling!
1752	 */
1753	write_lock_irq(&tasklist_lock);
1754
1755	/* CLONE_PARENT re-uses the old parent */
1756	if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1757		p->real_parent = current->real_parent;
1758		p->parent_exec_id = current->parent_exec_id;
1759	} else {
1760		p->real_parent = current;
1761		p->parent_exec_id = current->self_exec_id;
1762	}
1763
 
 
1764	spin_lock(&current->sighand->siglock);
1765
1766	/*
1767	 * Copy seccomp details explicitly here, in case they were changed
1768	 * before holding sighand lock.
1769	 */
1770	copy_seccomp(p);
1771
1772	/*
1773	 * Process group and session signals need to be delivered to just the
1774	 * parent before the fork or both the parent and the child after the
1775	 * fork. Restart if a signal comes in before we add the new process to
1776	 * it's process group.
1777	 * A fatal signal pending means that current will exit, so the new
1778	 * thread can't slip out of an OOM kill (or normal SIGKILL).
1779	*/
1780	recalc_sigpending();
1781	if (signal_pending(current)) {
1782		spin_unlock(&current->sighand->siglock);
1783		write_unlock_irq(&tasklist_lock);
1784		retval = -ERESTARTNOINTR;
1785		goto bad_fork_cancel_cgroup;
1786	}
1787
 
 
 
 
 
 
 
 
 
 
 
1788	if (likely(p->pid)) {
1789		ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1790
1791		init_task_pid(p, PIDTYPE_PID, pid);
1792		if (thread_group_leader(p)) {
 
1793			init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1794			init_task_pid(p, PIDTYPE_SID, task_session(current));
1795
1796			if (is_child_reaper(pid)) {
1797				ns_of_pid(pid)->child_reaper = p;
1798				p->signal->flags |= SIGNAL_UNKILLABLE;
1799			}
1800
1801			p->signal->leader_pid = pid;
1802			p->signal->tty = tty_kref_get(current->signal->tty);
 
 
 
 
 
 
 
1803			list_add_tail(&p->sibling, &p->real_parent->children);
1804			list_add_tail_rcu(&p->tasks, &init_task.tasks);
 
1805			attach_pid(p, PIDTYPE_PGID);
1806			attach_pid(p, PIDTYPE_SID);
1807			__this_cpu_inc(process_counts);
1808		} else {
1809			current->signal->nr_threads++;
1810			atomic_inc(&current->signal->live);
1811			atomic_inc(&current->signal->sigcnt);
 
1812			list_add_tail_rcu(&p->thread_group,
1813					  &p->group_leader->thread_group);
1814			list_add_tail_rcu(&p->thread_node,
1815					  &p->signal->thread_head);
1816		}
1817		attach_pid(p, PIDTYPE_PID);
1818		nr_threads++;
1819	}
1820
1821	total_forks++;
 
1822	spin_unlock(&current->sighand->siglock);
1823	syscall_tracepoint_update(p);
1824	write_unlock_irq(&tasklist_lock);
1825
1826	proc_fork_connector(p);
1827	cgroup_post_fork(p);
1828	threadgroup_change_end(current);
1829	perf_event_fork(p);
1830
1831	trace_task_newtask(p, clone_flags);
1832	uprobe_copy_process(p, clone_flags);
1833
1834	return p;
1835
1836bad_fork_cancel_cgroup:
1837	cgroup_cancel_fork(p);
 
 
 
 
 
 
 
1838bad_fork_free_pid:
1839	threadgroup_change_end(current);
1840	if (pid != &init_struct_pid)
1841		free_pid(pid);
1842bad_fork_cleanup_thread:
1843	exit_thread(p);
1844bad_fork_cleanup_io:
1845	if (p->io_context)
1846		exit_io_context(p);
1847bad_fork_cleanup_namespaces:
1848	exit_task_namespaces(p);
1849bad_fork_cleanup_mm:
1850	if (p->mm)
 
1851		mmput(p->mm);
 
1852bad_fork_cleanup_signal:
1853	if (!(clone_flags & CLONE_THREAD))
1854		free_signal_struct(p->signal);
1855bad_fork_cleanup_sighand:
1856	__cleanup_sighand(p->sighand);
1857bad_fork_cleanup_fs:
1858	exit_fs(p); /* blocking */
1859bad_fork_cleanup_files:
1860	exit_files(p); /* blocking */
1861bad_fork_cleanup_semundo:
1862	exit_sem(p);
 
 
1863bad_fork_cleanup_audit:
1864	audit_free(p);
1865bad_fork_cleanup_perf:
1866	perf_event_free_task(p);
1867bad_fork_cleanup_policy:
 
1868#ifdef CONFIG_NUMA
1869	mpol_put(p->mempolicy);
1870bad_fork_cleanup_threadgroup_lock:
1871#endif
1872	delayacct_tsk_free(p);
1873bad_fork_cleanup_count:
1874	atomic_dec(&p->cred->user->processes);
1875	exit_creds(p);
1876bad_fork_free:
1877	p->state = TASK_DEAD;
1878	put_task_stack(p);
1879	free_task(p);
1880fork_out:
 
 
 
1881	return ERR_PTR(retval);
1882}
1883
1884static inline void init_idle_pids(struct pid_link *links)
1885{
1886	enum pid_type type;
1887
1888	for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1889		INIT_HLIST_NODE(&links[type].node); /* not really needed */
1890		links[type].pid = &init_struct_pid;
1891	}
1892}
1893
1894struct task_struct *fork_idle(int cpu)
1895{
1896	struct task_struct *task;
1897	task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
1898			    cpu_to_node(cpu));
 
 
 
1899	if (!IS_ERR(task)) {
1900		init_idle_pids(task->pids);
1901		init_idle(task, cpu);
1902	}
1903
1904	return task;
1905}
1906
 
 
 
 
 
1907/*
1908 *  Ok, this is the main fork-routine.
1909 *
1910 * It copies the process, and if successful kick-starts
1911 * it and waits for it to finish using the VM if required.
 
 
1912 */
1913long _do_fork(unsigned long clone_flags,
1914	      unsigned long stack_start,
1915	      unsigned long stack_size,
1916	      int __user *parent_tidptr,
1917	      int __user *child_tidptr,
1918	      unsigned long tls)
1919{
 
 
 
1920	struct task_struct *p;
1921	int trace = 0;
1922	long nr;
1923
1924	/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1925	 * Determine whether and which event to report to ptracer.  When
1926	 * called from kernel_thread or CLONE_UNTRACED is explicitly
1927	 * requested, no event is reported; otherwise, report if the event
1928	 * for the type of forking is enabled.
1929	 */
1930	if (!(clone_flags & CLONE_UNTRACED)) {
1931		if (clone_flags & CLONE_VFORK)
1932			trace = PTRACE_EVENT_VFORK;
1933		else if ((clone_flags & CSIGNAL) != SIGCHLD)
1934			trace = PTRACE_EVENT_CLONE;
1935		else
1936			trace = PTRACE_EVENT_FORK;
1937
1938		if (likely(!ptrace_event_enabled(current, trace)))
1939			trace = 0;
1940	}
1941
1942	p = copy_process(clone_flags, stack_start, stack_size,
1943			 child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
1944	add_latent_entropy();
 
 
 
 
1945	/*
1946	 * Do this prior waking up the new thread - the thread pointer
1947	 * might get invalid after that point, if the thread exits quickly.
1948	 */
1949	if (!IS_ERR(p)) {
1950		struct completion vfork;
1951		struct pid *pid;
1952
1953		trace_sched_process_fork(current, p);
1954
1955		pid = get_task_pid(p, PIDTYPE_PID);
1956		nr = pid_vnr(pid);
1957
1958		if (clone_flags & CLONE_PARENT_SETTID)
1959			put_user(nr, parent_tidptr);
1960
1961		if (clone_flags & CLONE_VFORK) {
1962			p->vfork_done = &vfork;
1963			init_completion(&vfork);
1964			get_task_struct(p);
1965		}
1966
1967		wake_up_new_task(p);
 
1968
1969		/* forking complete and child started to run, tell ptracer */
1970		if (unlikely(trace))
1971			ptrace_event_pid(trace, pid);
1972
1973		if (clone_flags & CLONE_VFORK) {
1974			if (!wait_for_vfork_done(p, &vfork))
1975				ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
1976		}
1977
1978		put_pid(pid);
1979	} else {
1980		nr = PTR_ERR(p);
 
1981	}
1982	return nr;
1983}
1984
1985#ifndef CONFIG_HAVE_COPY_THREAD_TLS
1986/* For compatibility with architectures that call do_fork directly rather than
1987 * using the syscall entry points below. */
1988long do_fork(unsigned long clone_flags,
1989	      unsigned long stack_start,
1990	      unsigned long stack_size,
1991	      int __user *parent_tidptr,
1992	      int __user *child_tidptr)
1993{
1994	return _do_fork(clone_flags, stack_start, stack_size,
1995			parent_tidptr, child_tidptr, 0);
 
 
1996}
1997#endif
1998
1999/*
2000 * Create a kernel thread.
2001 */
2002pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2003{
2004	return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
2005		(unsigned long)arg, NULL, NULL, 0);
 
 
 
 
 
 
 
2006}
2007
2008#ifdef __ARCH_WANT_SYS_FORK
2009SYSCALL_DEFINE0(fork)
2010{
2011#ifdef CONFIG_MMU
2012	return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
 
 
 
 
2013#else
2014	/* can not support in nommu mode */
2015	return -EINVAL;
2016#endif
2017}
2018#endif
2019
2020#ifdef __ARCH_WANT_SYS_VFORK
2021SYSCALL_DEFINE0(vfork)
2022{
2023	return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
2024			0, NULL, NULL, 0);
 
 
 
 
2025}
2026#endif
2027
2028#ifdef __ARCH_WANT_SYS_CLONE
2029#ifdef CONFIG_CLONE_BACKWARDS
2030SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2031		 int __user *, parent_tidptr,
2032		 unsigned long, tls,
2033		 int __user *, child_tidptr)
2034#elif defined(CONFIG_CLONE_BACKWARDS2)
2035SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2036		 int __user *, parent_tidptr,
2037		 int __user *, child_tidptr,
2038		 unsigned long, tls)
2039#elif defined(CONFIG_CLONE_BACKWARDS3)
2040SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2041		int, stack_size,
2042		int __user *, parent_tidptr,
2043		int __user *, child_tidptr,
2044		unsigned long, tls)
2045#else
2046SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2047		 int __user *, parent_tidptr,
2048		 int __user *, child_tidptr,
2049		 unsigned long, tls)
2050#endif
2051{
2052	return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2053}
2054#endif
2055
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2056#ifndef ARCH_MIN_MMSTRUCT_ALIGN
2057#define ARCH_MIN_MMSTRUCT_ALIGN 0
2058#endif
2059
2060static void sighand_ctor(void *data)
2061{
2062	struct sighand_struct *sighand = data;
2063
2064	spin_lock_init(&sighand->siglock);
2065	init_waitqueue_head(&sighand->signalfd_wqh);
2066}
2067
2068void __init proc_caches_init(void)
2069{
 
 
2070	sighand_cachep = kmem_cache_create("sighand_cache",
2071			sizeof(struct sighand_struct), 0,
2072			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
2073			SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor);
2074	signal_cachep = kmem_cache_create("signal_cache",
2075			sizeof(struct signal_struct), 0,
2076			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2077			NULL);
2078	files_cachep = kmem_cache_create("files_cache",
2079			sizeof(struct files_struct), 0,
2080			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2081			NULL);
2082	fs_cachep = kmem_cache_create("fs_cache",
2083			sizeof(struct fs_struct), 0,
2084			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2085			NULL);
 
2086	/*
2087	 * FIXME! The "sizeof(struct mm_struct)" currently includes the
2088	 * whole struct cpumask for the OFFSTACK case. We could change
2089	 * this to *only* allocate as much of it as required by the
2090	 * maximum number of CPU's we can ever have.  The cpumask_allocation
2091	 * is at the end of the structure, exactly for that reason.
2092	 */
2093	mm_cachep = kmem_cache_create("mm_struct",
2094			sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
2095			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
 
 
2096			NULL);
2097	vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2098	mmap_init();
2099	nsproxy_cache_init();
2100}
2101
2102/*
2103 * Check constraints on flags passed to the unshare system call.
2104 */
2105static int check_unshare_flags(unsigned long unshare_flags)
2106{
2107	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2108				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2109				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2110				CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
 
2111		return -EINVAL;
2112	/*
2113	 * Not implemented, but pretend it works if there is nothing
2114	 * to unshare.  Note that unsharing the address space or the
2115	 * signal handlers also need to unshare the signal queues (aka
2116	 * CLONE_THREAD).
2117	 */
2118	if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2119		if (!thread_group_empty(current))
2120			return -EINVAL;
2121	}
2122	if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2123		if (atomic_read(&current->sighand->count) > 1)
2124			return -EINVAL;
2125	}
2126	if (unshare_flags & CLONE_VM) {
2127		if (!current_is_single_threaded())
2128			return -EINVAL;
2129	}
2130
2131	return 0;
2132}
2133
2134/*
2135 * Unshare the filesystem structure if it is being shared
2136 */
2137static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2138{
2139	struct fs_struct *fs = current->fs;
2140
2141	if (!(unshare_flags & CLONE_FS) || !fs)
2142		return 0;
2143
2144	/* don't need lock here; in the worst case we'll do useless copy */
2145	if (fs->users == 1)
2146		return 0;
2147
2148	*new_fsp = copy_fs_struct(fs);
2149	if (!*new_fsp)
2150		return -ENOMEM;
2151
2152	return 0;
2153}
2154
2155/*
2156 * Unshare file descriptor table if it is being shared
2157 */
2158static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
 
2159{
2160	struct files_struct *fd = current->files;
2161	int error = 0;
2162
2163	if ((unshare_flags & CLONE_FILES) &&
2164	    (fd && atomic_read(&fd->count) > 1)) {
2165		*new_fdp = dup_fd(fd, &error);
2166		if (!*new_fdp)
2167			return error;
2168	}
2169
2170	return 0;
2171}
2172
2173/*
2174 * unshare allows a process to 'unshare' part of the process
2175 * context which was originally shared using clone.  copy_*
2176 * functions used by do_fork() cannot be used here directly
2177 * because they modify an inactive task_struct that is being
2178 * constructed. Here we are modifying the current, active,
2179 * task_struct.
2180 */
2181SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2182{
2183	struct fs_struct *fs, *new_fs = NULL;
2184	struct files_struct *fd, *new_fd = NULL;
2185	struct cred *new_cred = NULL;
2186	struct nsproxy *new_nsproxy = NULL;
2187	int do_sysvsem = 0;
2188	int err;
2189
2190	/*
2191	 * If unsharing a user namespace must also unshare the thread group
2192	 * and unshare the filesystem root and working directories.
2193	 */
2194	if (unshare_flags & CLONE_NEWUSER)
2195		unshare_flags |= CLONE_THREAD | CLONE_FS;
2196	/*
2197	 * If unsharing vm, must also unshare signal handlers.
2198	 */
2199	if (unshare_flags & CLONE_VM)
2200		unshare_flags |= CLONE_SIGHAND;
2201	/*
2202	 * If unsharing a signal handlers, must also unshare the signal queues.
2203	 */
2204	if (unshare_flags & CLONE_SIGHAND)
2205		unshare_flags |= CLONE_THREAD;
2206	/*
2207	 * If unsharing namespace, must also unshare filesystem information.
2208	 */
2209	if (unshare_flags & CLONE_NEWNS)
2210		unshare_flags |= CLONE_FS;
2211
2212	err = check_unshare_flags(unshare_flags);
2213	if (err)
2214		goto bad_unshare_out;
2215	/*
2216	 * CLONE_NEWIPC must also detach from the undolist: after switching
2217	 * to a new ipc namespace, the semaphore arrays from the old
2218	 * namespace are unreachable.
2219	 */
2220	if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2221		do_sysvsem = 1;
2222	err = unshare_fs(unshare_flags, &new_fs);
2223	if (err)
2224		goto bad_unshare_out;
2225	err = unshare_fd(unshare_flags, &new_fd);
2226	if (err)
2227		goto bad_unshare_cleanup_fs;
2228	err = unshare_userns(unshare_flags, &new_cred);
2229	if (err)
2230		goto bad_unshare_cleanup_fd;
2231	err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2232					 new_cred, new_fs);
2233	if (err)
2234		goto bad_unshare_cleanup_cred;
2235
2236	if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2237		if (do_sysvsem) {
2238			/*
2239			 * CLONE_SYSVSEM is equivalent to sys_exit().
2240			 */
2241			exit_sem(current);
2242		}
2243		if (unshare_flags & CLONE_NEWIPC) {
2244			/* Orphan segments in old ns (see sem above). */
2245			exit_shm(current);
2246			shm_init_task(current);
2247		}
2248
2249		if (new_nsproxy)
2250			switch_task_namespaces(current, new_nsproxy);
2251
2252		task_lock(current);
2253
2254		if (new_fs) {
2255			fs = current->fs;
2256			spin_lock(&fs->lock);
2257			current->fs = new_fs;
2258			if (--fs->users)
2259				new_fs = NULL;
2260			else
2261				new_fs = fs;
2262			spin_unlock(&fs->lock);
2263		}
2264
2265		if (new_fd) {
2266			fd = current->files;
2267			current->files = new_fd;
2268			new_fd = fd;
2269		}
2270
2271		task_unlock(current);
2272
2273		if (new_cred) {
2274			/* Install the new user namespace */
2275			commit_creds(new_cred);
2276			new_cred = NULL;
2277		}
2278	}
2279
 
 
2280bad_unshare_cleanup_cred:
2281	if (new_cred)
2282		put_cred(new_cred);
2283bad_unshare_cleanup_fd:
2284	if (new_fd)
2285		put_files_struct(new_fd);
2286
2287bad_unshare_cleanup_fs:
2288	if (new_fs)
2289		free_fs_struct(new_fs);
2290
2291bad_unshare_out:
2292	return err;
2293}
2294
 
 
 
 
 
2295/*
2296 *	Helper to unshare the files of the current task.
2297 *	We don't want to expose copy_files internals to
2298 *	the exec layer of the kernel.
2299 */
2300
2301int unshare_files(struct files_struct **displaced)
2302{
2303	struct task_struct *task = current;
2304	struct files_struct *copy = NULL;
2305	int error;
2306
2307	error = unshare_fd(CLONE_FILES, &copy);
2308	if (error || !copy) {
2309		*displaced = NULL;
2310		return error;
2311	}
2312	*displaced = task->files;
2313	task_lock(task);
2314	task->files = copy;
2315	task_unlock(task);
2316	return 0;
2317}
2318
2319int sysctl_max_threads(struct ctl_table *table, int write,
2320		       void __user *buffer, size_t *lenp, loff_t *ppos)
2321{
2322	struct ctl_table t;
2323	int ret;
2324	int threads = max_threads;
2325	int min = MIN_THREADS;
2326	int max = MAX_THREADS;
2327
2328	t = *table;
2329	t.data = &threads;
2330	t.extra1 = &min;
2331	t.extra2 = &max;
2332
2333	ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2334	if (ret || !write)
2335		return ret;
2336
2337	set_max_threads(threads);
2338
2339	return 0;
2340}