fork.c 60.2 KB
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/*
 *  linux/kernel/fork.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 *  'fork.c' contains the help-routines for the 'fork' system call
 * (see also entry.S and others).
 * Fork is rather simple, once you get the hang of it, but the memory
 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
 */

#include <linux/slab.h>
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#include <linux/sched/autogroup.h>
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#include <linux/sched/mm.h>
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#include <linux/sched/coredump.h>
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#include <linux/sched/user.h>
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#include <linux/sched/numa_balancing.h>
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#include <linux/sched/stat.h>
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#include <linux/sched/task.h>
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#include <linux/sched/task_stack.h>
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#include <linux/sched/cputime.h>
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#include <linux/rtmutex.h>
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#include <linux/init.h>
#include <linux/unistd.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/completion.h>
#include <linux/personality.h>
#include <linux/mempolicy.h>
#include <linux/sem.h>
#include <linux/file.h>
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#include <linux/fdtable.h>
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#include <linux/iocontext.h>
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#include <linux/key.h>
#include <linux/binfmts.h>
#include <linux/mman.h>
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#include <linux/mmu_notifier.h>
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#include <linux/hmm.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
#include <linux/vmacache.h>
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#include <linux/nsproxy.h>
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#include <linux/capability.h>
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#include <linux/cpu.h>
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#include <linux/cgroup.h>
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#include <linux/security.h>
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#include <linux/hugetlb.h>
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#include <linux/seccomp.h>
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#include <linux/swap.h>
#include <linux/syscalls.h>
#include <linux/jiffies.h>
#include <linux/futex.h>
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#include <linux/compat.h>
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#include <linux/kthread.h>
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#include <linux/task_io_accounting_ops.h>
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#include <linux/rcupdate.h>
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#include <linux/ptrace.h>
#include <linux/mount.h>
#include <linux/audit.h>
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#include <linux/memcontrol.h>
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#include <linux/ftrace.h>
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#include <linux/proc_fs.h>
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#include <linux/profile.h>
#include <linux/rmap.h>
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#include <linux/ksm.h>
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#include <linux/acct.h>
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#include <linux/userfaultfd_k.h>
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#include <linux/tsacct_kern.h>
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#include <linux/cn_proc.h>
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#include <linux/freezer.h>
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#include <linux/delayacct.h>
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#include <linux/taskstats_kern.h>
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#include <linux/random.h>
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#include <linux/tty.h>
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#include <linux/blkdev.h>
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#include <linux/fs_struct.h>
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#include <linux/magic.h>
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#include <linux/sched/mm.h>
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#include <linux/perf_event.h>
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#include <linux/posix-timers.h>
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#include <linux/user-return-notifier.h>
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#include <linux/oom.h>
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#include <linux/khugepaged.h>
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#include <linux/signalfd.h>
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#include <linux/uprobes.h>
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#include <linux/aio.h>
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#include <linux/compiler.h>
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#include <linux/sysctl.h>
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#include <linux/kcov.h>
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#include <linux/livepatch.h>
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#include <linux/thread_info.h>
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#include <asm/pgtable.h>
#include <asm/pgalloc.h>
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#include <linux/uaccess.h>
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#include <asm/mmu_context.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>

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#include <trace/events/sched.h>

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#define CREATE_TRACE_POINTS
#include <trace/events/task.h>

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/*
 * Minimum number of threads to boot the kernel
 */
#define MIN_THREADS 20

/*
 * Maximum number of threads
 */
#define MAX_THREADS FUTEX_TID_MASK

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/*
 * Protected counters by write_lock_irq(&tasklist_lock)
 */
unsigned long total_forks;	/* Handle normal Linux uptimes. */
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int nr_threads;			/* The idle threads do not count.. */
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int max_threads;		/* tunable limit on nr_threads */

DEFINE_PER_CPU(unsigned long, process_counts) = 0;

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__cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
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#ifdef CONFIG_PROVE_RCU
int lockdep_tasklist_lock_is_held(void)
{
	return lockdep_is_held(&tasklist_lock);
}
EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
#endif /* #ifdef CONFIG_PROVE_RCU */
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int nr_processes(void)
{
	int cpu;
	int total = 0;

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	for_each_possible_cpu(cpu)
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		total += per_cpu(process_counts, cpu);

	return total;
}

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void __weak arch_release_task_struct(struct task_struct *tsk)
{
}

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#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
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static struct kmem_cache *task_struct_cachep;
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static inline struct task_struct *alloc_task_struct_node(int node)
{
	return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
}

static inline void free_task_struct(struct task_struct *tsk)
{
	kmem_cache_free(task_struct_cachep, tsk);
}
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#endif

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void __weak arch_release_thread_stack(unsigned long *stack)
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{
}

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#ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
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/*
 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
 * kmemcache based allocator.
 */
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# if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
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#ifdef CONFIG_VMAP_STACK
/*
 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
 * flush.  Try to minimize the number of calls by caching stacks.
 */
#define NR_CACHED_STACKS 2
static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
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static int free_vm_stack_cache(unsigned int cpu)
{
	struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
	int i;

	for (i = 0; i < NR_CACHED_STACKS; i++) {
		struct vm_struct *vm_stack = cached_vm_stacks[i];

		if (!vm_stack)
			continue;

		vfree(vm_stack->addr);
		cached_vm_stacks[i] = NULL;
	}

	return 0;
}
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#endif

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static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
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{
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#ifdef CONFIG_VMAP_STACK
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	void *stack;
	int i;

	for (i = 0; i < NR_CACHED_STACKS; i++) {
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		struct vm_struct *s;

		s = this_cpu_xchg(cached_stacks[i], NULL);
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		if (!s)
			continue;

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		/* Clear stale pointers from reused stack. */
		memset(s->addr, 0, THREAD_SIZE);
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		tsk->stack_vm_area = s;
		return s->addr;
	}

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	stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
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				     VMALLOC_START, VMALLOC_END,
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				     THREADINFO_GFP,
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				     PAGE_KERNEL,
				     0, node, __builtin_return_address(0));
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	/*
	 * We can't call find_vm_area() in interrupt context, and
	 * free_thread_stack() can be called in interrupt context,
	 * so cache the vm_struct.
	 */
	if (stack)
		tsk->stack_vm_area = find_vm_area(stack);
	return stack;
#else
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	struct page *page = alloc_pages_node(node, THREADINFO_GFP,
					     THREAD_SIZE_ORDER);
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	return page ? page_address(page) : NULL;
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#endif
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}

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static inline void free_thread_stack(struct task_struct *tsk)
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{
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#ifdef CONFIG_VMAP_STACK
	if (task_stack_vm_area(tsk)) {
		int i;

		for (i = 0; i < NR_CACHED_STACKS; i++) {
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			if (this_cpu_cmpxchg(cached_stacks[i],
					NULL, tsk->stack_vm_area) != NULL)
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				continue;

			return;
		}

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		vfree_atomic(tsk->stack);
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		return;
	}
#endif

	__free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
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}
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# else
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static struct kmem_cache *thread_stack_cache;
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static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
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						  int node)
{
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	return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
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}

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static void free_thread_stack(struct task_struct *tsk)
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{
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	kmem_cache_free(thread_stack_cache, tsk->stack);
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}

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void thread_stack_cache_init(void)
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{
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	thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
					THREAD_SIZE, THREAD_SIZE, 0, 0,
					THREAD_SIZE, NULL);
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	BUG_ON(thread_stack_cache == NULL);
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}
# endif
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#endif

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/* SLAB cache for signal_struct structures (tsk->signal) */
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static struct kmem_cache *signal_cachep;
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/* SLAB cache for sighand_struct structures (tsk->sighand) */
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struct kmem_cache *sighand_cachep;
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/* SLAB cache for files_struct structures (tsk->files) */
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struct kmem_cache *files_cachep;
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/* SLAB cache for fs_struct structures (tsk->fs) */
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struct kmem_cache *fs_cachep;
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/* SLAB cache for vm_area_struct structures */
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struct kmem_cache *vm_area_cachep;
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/* SLAB cache for mm_struct structures (tsk->mm) */
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static struct kmem_cache *mm_cachep;
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static void account_kernel_stack(struct task_struct *tsk, int account)
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{
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	void *stack = task_stack_page(tsk);
	struct vm_struct *vm = task_stack_vm_area(tsk);

	BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);

	if (vm) {
		int i;

		BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);

		for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
			mod_zone_page_state(page_zone(vm->pages[i]),
					    NR_KERNEL_STACK_KB,
					    PAGE_SIZE / 1024 * account);
		}

		/* All stack pages belong to the same memcg. */
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		mod_memcg_page_state(vm->pages[0], MEMCG_KERNEL_STACK_KB,
				     account * (THREAD_SIZE / 1024));
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	} else {
		/*
		 * All stack pages are in the same zone and belong to the
		 * same memcg.
		 */
		struct page *first_page = virt_to_page(stack);

		mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
				    THREAD_SIZE / 1024 * account);

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		mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB,
				     account * (THREAD_SIZE / 1024));
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	}
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}

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static void release_task_stack(struct task_struct *tsk)
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{
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	if (WARN_ON(tsk->state != TASK_DEAD))
		return;  /* Better to leak the stack than to free prematurely */

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	account_kernel_stack(tsk, -1);
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	arch_release_thread_stack(tsk->stack);
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	free_thread_stack(tsk);
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	tsk->stack = NULL;
#ifdef CONFIG_VMAP_STACK
	tsk->stack_vm_area = NULL;
#endif
}

#ifdef CONFIG_THREAD_INFO_IN_TASK
void put_task_stack(struct task_struct *tsk)
{
	if (atomic_dec_and_test(&tsk->stack_refcount))
		release_task_stack(tsk);
}
#endif

void free_task(struct task_struct *tsk)
{
#ifndef CONFIG_THREAD_INFO_IN_TASK
	/*
	 * The task is finally done with both the stack and thread_info,
	 * so free both.
	 */
	release_task_stack(tsk);
#else
	/*
	 * If the task had a separate stack allocation, it should be gone
	 * by now.
	 */
	WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0);
#endif
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	rt_mutex_debug_task_free(tsk);
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	ftrace_graph_exit_task(tsk);
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	put_seccomp_filter(tsk);
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	arch_release_task_struct(tsk);
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	if (tsk->flags & PF_KTHREAD)
		free_kthread_struct(tsk);
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	free_task_struct(tsk);
}
EXPORT_SYMBOL(free_task);

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#ifdef CONFIG_MMU
static __latent_entropy int dup_mmap(struct mm_struct *mm,
					struct mm_struct *oldmm)
{
	struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
	struct rb_node **rb_link, *rb_parent;
	int retval;
	unsigned long charge;
	LIST_HEAD(uf);

	uprobe_start_dup_mmap();
	if (down_write_killable(&oldmm->mmap_sem)) {
		retval = -EINTR;
		goto fail_uprobe_end;
	}
	flush_cache_dup_mm(oldmm);
	uprobe_dup_mmap(oldmm, mm);
	/*
	 * Not linked in yet - no deadlock potential:
	 */
	down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);

	/* No ordering required: file already has been exposed. */
	RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));

	mm->total_vm = oldmm->total_vm;
	mm->data_vm = oldmm->data_vm;
	mm->exec_vm = oldmm->exec_vm;
	mm->stack_vm = oldmm->stack_vm;

	rb_link = &mm->mm_rb.rb_node;
	rb_parent = NULL;
	pprev = &mm->mmap;
	retval = ksm_fork(mm, oldmm);
	if (retval)
		goto out;
	retval = khugepaged_fork(mm, oldmm);
	if (retval)
		goto out;

	prev = NULL;
	for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
		struct file *file;

		if (mpnt->vm_flags & VM_DONTCOPY) {
			vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
			continue;
		}
		charge = 0;
		if (mpnt->vm_flags & VM_ACCOUNT) {
			unsigned long len = vma_pages(mpnt);

			if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
				goto fail_nomem;
			charge = len;
		}
		tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
		if (!tmp)
			goto fail_nomem;
		*tmp = *mpnt;
		INIT_LIST_HEAD(&tmp->anon_vma_chain);
		retval = vma_dup_policy(mpnt, tmp);
		if (retval)
			goto fail_nomem_policy;
		tmp->vm_mm = mm;
		retval = dup_userfaultfd(tmp, &uf);
		if (retval)
			goto fail_nomem_anon_vma_fork;
		if (tmp->vm_flags & VM_WIPEONFORK) {
			/* VM_WIPEONFORK gets a clean slate in the child. */
			tmp->anon_vma = NULL;
			if (anon_vma_prepare(tmp))
				goto fail_nomem_anon_vma_fork;
		} else if (anon_vma_fork(tmp, mpnt))
			goto fail_nomem_anon_vma_fork;
		tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
		tmp->vm_next = tmp->vm_prev = NULL;
		file = tmp->vm_file;
		if (file) {
			struct inode *inode = file_inode(file);
			struct address_space *mapping = file->f_mapping;

			get_file(file);
			if (tmp->vm_flags & VM_DENYWRITE)
				atomic_dec(&inode->i_writecount);
			i_mmap_lock_write(mapping);
			if (tmp->vm_flags & VM_SHARED)
				atomic_inc(&mapping->i_mmap_writable);
			flush_dcache_mmap_lock(mapping);
			/* insert tmp into the share list, just after mpnt */
			vma_interval_tree_insert_after(tmp, mpnt,
					&mapping->i_mmap);
			flush_dcache_mmap_unlock(mapping);
			i_mmap_unlock_write(mapping);
		}

		/*
		 * Clear hugetlb-related page reserves for children. This only
		 * affects MAP_PRIVATE mappings. Faults generated by the child
		 * are not guaranteed to succeed, even if read-only
		 */
		if (is_vm_hugetlb_page(tmp))
			reset_vma_resv_huge_pages(tmp);

		/*
		 * Link in the new vma and copy the page table entries.
		 */
		*pprev = tmp;
		pprev = &tmp->vm_next;
		tmp->vm_prev = prev;
		prev = tmp;

		__vma_link_rb(mm, tmp, rb_link, rb_parent);
		rb_link = &tmp->vm_rb.rb_right;
		rb_parent = &tmp->vm_rb;

		mm->map_count++;
		if (!(tmp->vm_flags & VM_WIPEONFORK))
			retval = copy_page_range(mm, oldmm, mpnt);

		if (tmp->vm_ops && tmp->vm_ops->open)
			tmp->vm_ops->open(tmp);

		if (retval)
			goto out;
	}
	/* a new mm has just been created */
	arch_dup_mmap(oldmm, mm);
	retval = 0;
out:
	up_write(&mm->mmap_sem);
	flush_tlb_mm(oldmm);
	up_write(&oldmm->mmap_sem);
	dup_userfaultfd_complete(&uf);
fail_uprobe_end:
	uprobe_end_dup_mmap();
	return retval;
fail_nomem_anon_vma_fork:
	mpol_put(vma_policy(tmp));
fail_nomem_policy:
	kmem_cache_free(vm_area_cachep, tmp);
fail_nomem:
	retval = -ENOMEM;
	vm_unacct_memory(charge);
	goto out;
}

static inline int mm_alloc_pgd(struct mm_struct *mm)
{
	mm->pgd = pgd_alloc(mm);
	if (unlikely(!mm->pgd))
		return -ENOMEM;
	return 0;
}

static inline void mm_free_pgd(struct mm_struct *mm)
{
	pgd_free(mm, mm->pgd);
}
#else
static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
{
	down_write(&oldmm->mmap_sem);
	RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
	up_write(&oldmm->mmap_sem);
	return 0;
}
#define mm_alloc_pgd(mm)	(0)
#define mm_free_pgd(mm)
#endif /* CONFIG_MMU */

static void check_mm(struct mm_struct *mm)
{
	int i;

	for (i = 0; i < NR_MM_COUNTERS; i++) {
		long x = atomic_long_read(&mm->rss_stat.count[i]);

		if (unlikely(x))
			printk(KERN_ALERT "BUG: Bad rss-counter state "
					  "mm:%p idx:%d val:%ld\n", mm, i, x);
	}

	if (mm_pgtables_bytes(mm))
		pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
				mm_pgtables_bytes(mm));

#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
	VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
#endif
}

#define allocate_mm()	(kmem_cache_alloc(mm_cachep, GFP_KERNEL))
#define free_mm(mm)	(kmem_cache_free(mm_cachep, (mm)))

/*
 * Called when the last reference to the mm
 * is dropped: either by a lazy thread or by
 * mmput. Free the page directory and the mm.
 */
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void __mmdrop(struct mm_struct *mm)
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{
	BUG_ON(mm == &init_mm);
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	WARN_ON_ONCE(mm == current->mm);
	WARN_ON_ONCE(mm == current->active_mm);
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	mm_free_pgd(mm);
	destroy_context(mm);
	hmm_mm_destroy(mm);
	mmu_notifier_mm_destroy(mm);
	check_mm(mm);
	put_user_ns(mm->user_ns);
	free_mm(mm);
}
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EXPORT_SYMBOL_GPL(__mmdrop);
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static void mmdrop_async_fn(struct work_struct *work)
{
	struct mm_struct *mm;

	mm = container_of(work, struct mm_struct, async_put_work);
	__mmdrop(mm);
}

static void mmdrop_async(struct mm_struct *mm)
{
	if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
		INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
		schedule_work(&mm->async_put_work);
	}
}

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static inline void free_signal_struct(struct signal_struct *sig)
{
627
	taskstats_tgid_free(sig);
628
	sched_autogroup_exit(sig);
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	/*
	 * __mmdrop is not safe to call from softirq context on x86 due to
	 * pgd_dtor so postpone it to the async context
	 */
633
	if (sig->oom_mm)
634
		mmdrop_async(sig->oom_mm);
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	kmem_cache_free(signal_cachep, sig);
}

static inline void put_signal_struct(struct signal_struct *sig)
{
640
	if (atomic_dec_and_test(&sig->sigcnt))
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		free_signal_struct(sig);
}

644
void __put_task_struct(struct task_struct *tsk)
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{
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	WARN_ON(!tsk->exit_state);
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	WARN_ON(atomic_read(&tsk->usage));
	WARN_ON(tsk == current);

650
	cgroup_free(tsk);
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	task_numa_free(tsk);
652
	security_task_free(tsk);
653
	exit_creds(tsk);
654
	delayacct_tsk_free(tsk);
655
	put_signal_struct(tsk->signal);
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	if (!profile_handoff_task(tsk))
		free_task(tsk);
}
660
EXPORT_SYMBOL_GPL(__put_task_struct);
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662
void __init __weak arch_task_cache_init(void) { }
663

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/*
 * set_max_threads
 */
667
static void set_max_threads(unsigned int max_threads_suggested)
668
{
669
	u64 threads;
670 671

	/*
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	 * The number of threads shall be limited such that the thread
	 * structures may only consume a small part of the available memory.
674
	 */
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	if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
		threads = MAX_THREADS;
	else
		threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
				    (u64) THREAD_SIZE * 8UL);

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	if (threads > max_threads_suggested)
		threads = max_threads_suggested;

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	max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
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}

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#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
/* Initialized by the architecture: */
int arch_task_struct_size __read_mostly;
#endif
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static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
{
	/* Fetch thread_struct whitelist for the architecture. */
	arch_thread_struct_whitelist(offset, size);

	/*
	 * Handle zero-sized whitelist or empty thread_struct, otherwise
	 * adjust offset to position of thread_struct in task_struct.
	 */
	if (unlikely(*size == 0))
		*offset = 0;
	else
		*offset += offsetof(struct task_struct, thread);
}

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void __init fork_init(void)
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{
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	int i;
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#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
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#ifndef ARCH_MIN_TASKALIGN
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#define ARCH_MIN_TASKALIGN	0
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#endif
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	int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
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	unsigned long useroffset, usersize;
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	/* create a slab on which task_structs can be allocated */
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	task_struct_whitelist(&useroffset, &usersize);
	task_struct_cachep = kmem_cache_create_usercopy("task_struct",
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			arch_task_struct_size, align,
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			SLAB_PANIC|SLAB_ACCOUNT,
			useroffset, usersize, NULL);
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#endif

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	/* do the arch specific task caches init */
	arch_task_cache_init();

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	set_max_threads(MAX_THREADS);
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	init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
	init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
	init_task.signal->rlim[RLIMIT_SIGPENDING] =
		init_task.signal->rlim[RLIMIT_NPROC];
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	for (i = 0; i < UCOUNT_COUNTS; i++) {
		init_user_ns.ucount_max[i] = max_threads/2;
	}
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#ifdef CONFIG_VMAP_STACK
	cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
			  NULL, free_vm_stack_cache);
#endif
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	lockdep_init_task(&init_task);
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}

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int __weak arch_dup_task_struct(struct task_struct *dst,
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					       struct task_struct *src)
{
	*dst = *src;
	return 0;
}

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void set_task_stack_end_magic(struct task_struct *tsk)
{
	unsigned long *stackend;

	stackend = end_of_stack(tsk);
	*stackend = STACK_END_MAGIC;	/* for overflow detection */
}

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static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
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{
	struct task_struct *tsk;
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	unsigned long *stack;
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	struct vm_struct *stack_vm_area;
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	int err;
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	if (node == NUMA_NO_NODE)
		node = tsk_fork_get_node(orig);
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	tsk = alloc_task_struct_node(node);
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	if (!tsk)
		return NULL;

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	stack = alloc_thread_stack_node(tsk, node);
	if (!stack)
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		goto free_tsk;
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	stack_vm_area = task_stack_vm_area(tsk);

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	err = arch_dup_task_struct(tsk, orig);
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	/*
	 * arch_dup_task_struct() clobbers the stack-related fields.  Make
	 * sure they're properly initialized before using any stack-related
	 * functions again.
	 */
	tsk->stack = stack;
#ifdef CONFIG_VMAP_STACK
	tsk->stack_vm_area = stack_vm_area;
#endif
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#ifdef CONFIG_THREAD_INFO_IN_TASK
	atomic_set(&tsk->stack_refcount, 1);
#endif
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796
	if (err)
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		goto free_stack;
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#ifdef CONFIG_SECCOMP
	/*
	 * We must handle setting up seccomp filters once we're under
	 * the sighand lock in case orig has changed between now and
	 * then. Until then, filter must be NULL to avoid messing up
	 * the usage counts on the error path calling free_task.
	 */
	tsk->seccomp.filter = NULL;
#endif
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	setup_thread_stack(tsk, orig);
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	clear_user_return_notifier(tsk);
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	clear_tsk_need_resched(tsk);
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	set_task_stack_end_magic(tsk);
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#ifdef CONFIG_CC_STACKPROTECTOR
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	tsk->stack_canary = get_random_canary();
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#endif

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	/*
	 * One for us, one for whoever does the "release_task()" (usually
	 * parent)
	 */
	atomic_set(&tsk->usage, 2);
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#ifdef CONFIG_BLK_DEV_IO_TRACE
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	tsk->btrace_seq = 0;
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#endif
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	tsk->splice_pipe = NULL;
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	tsk->task_frag.page = NULL;
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	tsk->wake_q.next = NULL;
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	account_kernel_stack(tsk, 1);
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	kcov_task_init(tsk);

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#ifdef CONFIG_FAULT_INJECTION
	tsk->fail_nth = 0;
#endif

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	return tsk;
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free_stack:
841
	free_thread_stack(tsk);
842
free_tsk:
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	free_task_struct(tsk);
	return NULL;
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}

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__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
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static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;

static int __init coredump_filter_setup(char *s)
{
	default_dump_filter =
		(simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
		MMF_DUMP_FILTER_MASK;
	return 1;
}

__setup("coredump_filter=", coredump_filter_setup);

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#include <linux/init_task.h>

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static void mm_init_aio(struct mm_struct *mm)
{
#ifdef CONFIG_AIO
	spin_lock_init(&mm->ioctx_lock);
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	mm->ioctx_table = NULL;
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#endif
}

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static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
{
#ifdef CONFIG_MEMCG
	mm->owner = p;
#endif
}

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static void mm_init_uprobes_state(struct mm_struct *mm)
{
#ifdef CONFIG_UPROBES
	mm->uprobes_state.xol_area = NULL;
#endif
}

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static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
	struct user_namespace *user_ns)
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{
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	mm->mmap = NULL;
	mm->mm_rb = RB_ROOT;
	mm->vmacache_seqnum = 0;
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	atomic_set(&mm->mm_users, 1);
	atomic_set(&mm->mm_count, 1);
	init_rwsem(&mm->mmap_sem);
	INIT_LIST_HEAD(&mm->mmlist);
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	mm->core_state = NULL;
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	mm_pgtables_bytes_init(mm);
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	mm->map_count = 0;
	mm->locked_vm = 0;
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	mm->pinned_vm = 0;
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	memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
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	spin_lock_init(&mm->page_table_lock);
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	mm_init_cpumask(mm);
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	mm_init_aio(mm);
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	mm_init_owner(mm, p);
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	RCU_INIT_POINTER(mm->exe_file, NULL);
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	mmu_notifier_mm_init(mm);
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	hmm_mm_init(mm);
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	init_tlb_flush_pending(mm);
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#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
	mm->pmd_huge_pte = NULL;
#endif
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	mm_init_uprobes_state(mm);
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	if (current->mm) {
		mm->flags = current->mm->flags & MMF_INIT_MASK;
		mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
	} else {
		mm->flags = default_dump_filter;
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		mm->def_flags = 0;
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	}

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	if (mm_alloc_pgd(mm))
		goto fail_nopgd;

	if (init_new_context(p, mm))
		goto fail_nocontext;
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	mm->user_ns = get_user_ns(user_ns);
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	return mm;

fail_nocontext:
	mm_free_pgd(mm);
fail_nopgd:
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	free_mm(mm);
	return NULL;
}

/*
 * Allocate and initialize an mm_struct.
 */
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struct mm_struct *mm_alloc(void)
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{
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	struct mm_struct *mm;
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	mm = allocate_mm();
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	if (!mm)
		return NULL;

	memset(mm, 0, sizeof(*mm));
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	return mm_init(mm, current, current_user_ns());
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}

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static inline void __mmput(struct mm_struct *mm)
{
	VM_BUG_ON(atomic_read(&mm->mm_users));

	uprobe_clear_state(mm);
	exit_aio(mm);
	ksm_exit(mm);
	khugepaged_exit(mm); /* must run before exit_mmap */
	exit_mmap(mm);
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	mm_put_huge_zero_page(mm);
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	set_mm_exe_file(mm, NULL);
	if (!list_empty(&mm->mmlist)) {
		spin_lock(&mmlist_lock);
		list_del(&mm->mmlist);
		spin_unlock(&mmlist_lock);
	}
	if (mm->binfmt)
		module_put(mm->binfmt->module);
	mmdrop(mm);
}

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/*
 * Decrement the use count and release all resources for an mm.
 */
void mmput(struct mm_struct *mm)
{
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	might_sleep();

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	if (atomic_dec_and_test(&mm->mm_users))
		__mmput(mm);
}
EXPORT_SYMBOL_GPL(mmput);

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#ifdef CONFIG_MMU
static void mmput_async_fn(struct work_struct *work)
{
	struct mm_struct *mm = container_of(work, struct mm_struct,
					    async_put_work);

	__mmput(mm);
}

void mmput_async(struct mm_struct *mm)
{
	if (atomic_dec_and_test(&mm->mm_users)) {
		INIT_WORK(&mm->async_put_work, mmput_async_fn);
		schedule_work(&mm->async_put_work);
	}
}
#endif

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/**
 * set_mm_exe_file - change a reference to the mm's executable file
 *
 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
 *
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 * Main users are mmput() and sys_execve(). Callers prevent concurrent
 * invocations: in mmput() nobody alive left, in execve task is single
 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
 * mm->exe_file, but does so without using set_mm_exe_file() in order
 * to do avoid the need for any locks.
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 */
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void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
{
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	struct file *old_exe_file;

	/*
	 * It is safe to dereference the exe_file without RCU as
	 * this function is only called if nobody else can access
	 * this mm -- see comment above for justification.
	 */
	old_exe_file = rcu_dereference_raw(mm->exe_file);
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	if (new_exe_file)
		get_file(new_exe_file);
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	rcu_assign_pointer(mm->exe_file, new_exe_file);
	if (old_exe_file)
		fput(old_exe_file);
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}

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/**
 * get_mm_exe_file - acquire a reference to the mm's executable file
 *
 * Returns %NULL if mm has no associated executable file.
 * User must release file via fput().
 */
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struct file *get_mm_exe_file(struct mm_struct *mm)
{
	struct file *exe_file;

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	rcu_read_lock();
	exe_file = rcu_dereference(mm->exe_file);
	if (exe_file && !get_file_rcu(exe_file))
		exe_file = NULL;
	rcu_read_unlock();
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	return exe_file;
}
1050
EXPORT_SYMBOL(get_mm_exe_file);
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/**
 * get_task_exe_file - acquire a reference to the task's executable file
 *
 * Returns %NULL if task's mm (if any) has no associated executable file or
 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
 * User must release file via fput().
 */
struct file *get_task_exe_file(struct task_struct *task)
{
	struct file *exe_file = NULL;
	struct mm_struct *mm;

	task_lock(task);
	mm = task->mm;
	if (mm) {
		if (!(task->flags & PF_KTHREAD))
			exe_file = get_mm_exe_file(mm);
	}
	task_unlock(task);
	return exe_file;
}
EXPORT_SYMBOL(get_task_exe_file);
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/**
 * get_task_mm - acquire a reference to the task's mm
 *
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 * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
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 * this kernel workthread has transiently adopted a user mm with use_mm,
 * to do its AIO) is not set and if so returns a reference to it, after
 * bumping up the use count.  User must release the mm via mmput()
 * after use.  Typically used by /proc and ptrace.
 */
struct mm_struct *get_task_mm(struct task_struct *task)
{
	struct mm_struct *mm;

	task_lock(task);
	mm = task->mm;
	if (mm) {
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		if (task->flags & PF_KTHREAD)
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			mm = NULL;
		else
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			mmget(mm);
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	}
	task_unlock(task);
	return mm;
}
EXPORT_SYMBOL_GPL(get_task_mm);

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struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
{
	struct mm_struct *mm;
	int err;

	err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
	if (err)
		return ERR_PTR(err);

	mm = get_task_mm(task);
	if (mm && mm != current->mm &&
			!ptrace_may_access(task, mode)) {
		mmput(mm);
		mm = ERR_PTR(-EACCES);
	}
	mutex_unlock(&task->signal->cred_guard_mutex);

	return mm;
}

1121
static void complete_vfork_done(struct task_struct *tsk)
1122
{
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	struct completion *vfork;
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	task_lock(tsk);
	vfork = tsk->vfork_done;
	if (likely(vfork)) {
		tsk->vfork_done = NULL;
		complete(vfork);
	}
	task_unlock(tsk);
}

static int wait_for_vfork_done(struct task_struct *child,
				struct completion *vfork)
{
	int killed;

	freezer_do_not_count();
	killed = wait_for_completion_killable(vfork);
	freezer_count();

	if (killed) {
		task_lock(child);
		child->vfork_done = NULL;
		task_unlock(child);
	}

	put_task_struct(child);
	return killed;
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}

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/* Please note the differences between mmput and mm_release.
 * mmput is called whenever we stop holding onto a mm_struct,
 * error success whatever.
 *
 * mm_release is called after a mm_struct has been removed
 * from the current process.
 *
 * This difference is important for error handling, when we
 * only half set up a mm_struct for a new process and need to restore
 * the old one.  Because we mmput the new mm_struct before
 * restoring the old one. . .
 * Eric Biederman 10 January 1998
 */
void mm_release(struct task_struct *tsk, struct mm_struct *mm)
{
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	/* Get rid of any futexes when releasing the mm */
#ifdef CONFIG_FUTEX
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	if (unlikely(tsk->robust_list)) {
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		exit_robust_list(tsk);
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		tsk->robust_list = NULL;
	}
1174
#ifdef CONFIG_COMPAT
1175
	if (unlikely(tsk->compat_robust_list)) {
1176
		compat_exit_robust_list(tsk);
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		tsk->compat_robust_list = NULL;
	}
1179
#endif
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	if (unlikely(!list_empty(&tsk->pi_state_list)))
		exit_pi_state_list(tsk);
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#endif

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	uprobe_free_utask(tsk);

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	/* Get rid of any cached register state */
	deactivate_mm(tsk, mm);

1189
	/*
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	 * Signal userspace if we're not exiting with a core dump
	 * because we want to leave the value intact for debugging
	 * purposes.
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	 */
1194
	if (tsk->clear_child_tid) {
1195
		if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
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		    atomic_read(&mm->mm_users) > 1) {
			/*
			 * We don't check the error code - if userspace has
			 * not set up a proper pointer then tough luck.
			 */
			put_user(0, tsk->clear_child_tid);
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			do_futex(tsk->clear_child_tid, FUTEX_WAKE,
					1, NULL, NULL, 0, 0);
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		}
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		tsk->clear_child_tid = NULL;
	}
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	/*
	 * All done, finally we can wake up parent and return this mm to him.
	 * Also kthread_stop() uses this completion for synchronization.
	 */
	if (tsk->vfork_done)
		complete_vfork_done(tsk);
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}

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/*
 * Allocate a new mm structure and copy contents from the
 * mm structure of the passed in task structure.
 */
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static struct mm_struct *dup_mm(struct task_struct *tsk)
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{
	struct mm_struct *mm, *oldmm = current->mm;
	int err;

	mm = allocate_mm();
	if (!mm)
		goto fail_nomem;

	memcpy(mm, oldmm, sizeof(*mm));

1231
	if (!mm_init(mm, tsk, mm->user_ns))
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		goto fail_nomem;

	err = dup_mmap(mm, oldmm);
	if (err)
		goto free_pt;

	mm->hiwater_rss = get_mm_rss(mm);
	mm->hiwater_vm = mm->total_vm;

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	if (mm->binfmt && !try_module_get(mm->binfmt->module))
		goto free_pt;

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	return mm;

free_pt:
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	/* don't put binfmt in mmput, we haven't got module yet */
	mm->binfmt = NULL;
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	mmput(mm);

fail_nomem:
	return NULL;
}

1255
static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
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{
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	struct mm_struct *mm, *oldmm;
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	int retval;

	tsk->min_flt = tsk->maj_flt = 0;
	tsk->nvcsw = tsk->nivcsw = 0;
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#ifdef CONFIG_DETECT_HUNG_TASK
	tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
#endif
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	tsk->mm = NULL;
	tsk->active_mm = NULL;

	/*
	 * Are we cloning a kernel thread?
	 *
	 * We need to steal a active VM for that..
	 */
	oldmm = current->mm;
	if (!oldmm)
		return 0;

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	/* initialize the new vmacache entries */
	vmacache_flush(tsk);

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	if (clone_flags & CLONE_VM) {
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		mmget(oldmm);
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		mm = oldmm;
		goto good_mm;
	}

	retval = -ENOMEM;
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	mm = dup_mm(tsk);
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	if (!mm)
		goto fail_nomem;

good_mm:
	tsk->mm = mm;
	tsk->active_mm = mm;
	return 0;

fail_nomem:
	return retval;
}

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static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
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{
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	struct fs_struct *fs = current->fs;
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	if (clone_flags & CLONE_FS) {
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		/* tsk->fs is already what we want */
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		spin_lock(&fs->lock);
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		if (fs->in_exec) {
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			spin_unlock(&fs->lock);
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			return -EAGAIN;
		}
		fs->users++;
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		spin_unlock(&fs->lock);
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		return 0;
	}
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	tsk->fs = copy_fs_struct(fs);
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	if (!tsk->fs)
		return -ENOMEM;
	return 0;
}

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static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
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{
	struct files_struct *oldf, *newf;
	int error = 0;

	/*
	 * A background process may not have any files ...
	 */
	oldf = current->files;
	if (!oldf)
		goto out;

	if (clone_flags & CLONE_FILES) {
		atomic_inc(&oldf->count);
		goto out;
	}

	newf = dup_fd(oldf, &error);
	if (!newf)
		goto out;

	tsk->files = newf;
	error = 0;
out:
	return error;
}

1348
static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
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{
#ifdef CONFIG_BLOCK
	struct io_context *ioc = current->io_context;
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	struct io_context *new_ioc;
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	if (!ioc)
		return 0;
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	/*
	 * Share io context with parent, if CLONE_IO is set
	 */
	if (clone_flags & CLONE_IO) {
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		ioc_task_link(ioc);
		tsk->io_context = ioc;
1362
	} else if (ioprio_valid(ioc->ioprio)) {
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		new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
		if (unlikely(!new_ioc))
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			return -ENOMEM;

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		new_ioc->ioprio = ioc->ioprio;
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		put_io_context(new_ioc);
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	}
#endif
	return 0;
}

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static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
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{
	struct sighand_struct *sig;

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	if (clone_flags & CLONE_SIGHAND) {
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		atomic_inc(&current->sighand->count);
		return 0;
	}
	sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
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	rcu_assign_pointer(tsk->sighand, sig);
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	if (!sig)
		return -ENOMEM;
1386

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	atomic_set(&sig->count, 1);
	memcpy(sig->action, current->sighand->action, sizeof(sig->action));
	return 0;
}

1392
void __cleanup_sighand(struct sighand_struct *sighand)
1393
{
1394 1395
	if (atomic_dec_and_test(&sighand->count)) {
		signalfd_cleanup(sighand);
1396
		/*
1397
		 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
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		 * without an RCU grace period, see __lock_task_sighand().
		 */
1400
		kmem_cache_free(sighand_cachep, sighand);
1401
	}
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}

1404
#ifdef CONFIG_POSIX_TIMERS
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/*
 * Initialize POSIX timer handling for a thread group.
 */
static void posix_cpu_timers_init_group(struct signal_struct *sig)
{
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	unsigned long cpu_limit;

1412
	cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1413
	if (cpu_limit != RLIM_INFINITY) {
1414
		sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC;
1415
		sig->cputimer.running = true;
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	}

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	/* The timer lists. */
	INIT_LIST_HEAD(&sig->cpu_timers[0]);
	INIT_LIST_HEAD(&sig->cpu_timers[1]);
	INIT_LIST_HEAD(&sig->cpu_timers[2]);
}
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#else
static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { }
#endif
1426

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static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
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{
	struct signal_struct *sig;

1431
	if (clone_flags & CLONE_THREAD)
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		return 0;

1434
	sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
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	tsk->signal = sig;
	if (!sig)
		return -ENOMEM;

1439
	sig->nr_threads = 1;
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	atomic_set(&sig->live, 1);
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	atomic_set(&sig->sigcnt, 1);
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	/* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
	sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
	tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);

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	init_waitqueue_head(&sig->wait_chldexit);
1448
	sig->curr_target = tsk;
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	init_sigpending(&sig->shared_pending);
1450
	seqlock_init(&sig->stats_lock);
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	prev_cputime_init(&sig->prev_cputime);
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1453
#ifdef CONFIG_POSIX_TIMERS
1454
	INIT_LIST_HEAD(&sig->posix_timers);
1455
	hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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	sig->real_timer.function = it_real_fn;
1457
#endif
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	task_lock(current->group_leader);
	memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
	task_unlock(current->group_leader);

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	posix_cpu_timers_init_group(sig);

1465
	tty_audit_fork(sig);
1466
	sched_autogroup_fork(sig);
1467

1468
	sig->oom_score_adj = current->signal->oom_score_adj;
1469
	sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1470

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	mutex_init(&sig->cred_guard_mutex);

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	return 0;
}

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static void copy_seccomp(struct task_struct *p)
{
#ifdef CONFIG_SECCOMP
	/*
	 * Must be called with sighand->lock held, which is common to
	 * all threads in the group. Holding cred_guard_mutex is not
	 * needed because this new task is not yet running and cannot
	 * be racing exec.
	 */
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	assert_spin_locked(&current->sighand->siglock);
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	/* Ref-count the new filter user, and assign it. */
	get_seccomp_filter(current);
	p->seccomp = current->seccomp;

	/*
	 * Explicitly enable no_new_privs here in case it got set
	 * between the task_struct being duplicated and holding the
	 * sighand lock. The seccomp state and nnp must be in sync.
	 */
	if (task_no_new_privs(current))
		task_set_no_new_privs(p);

	/*
	 * If the parent gained a seccomp mode after copying thread
	 * flags and between before we held the sighand lock, we have
	 * to manually enable the seccomp thread flag here.
	 */
	if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
		set_tsk_thread_flag(p, TIF_SECCOMP);
#endif
}

1509
SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
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{
	current->clear_child_tid = tidptr;

1513
	return task_pid_vnr(current);
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}

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1516
static void rt_mutex_init_task(struct task_struct *p)
1517
{
1518
	raw_spin_lock_init(&p->pi_lock);
1519
#ifdef CONFIG_RT_MUTEXES
1520
	p->pi_waiters = RB_ROOT_CACHED;
1521
	p->pi_top_task = NULL;
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	p->pi_blocked_on = NULL;
#endif
}

1526
#ifdef CONFIG_POSIX_TIMERS
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/*
 * Initialize POSIX timer handling for a single task.
 */
static void posix_cpu_timers_init(struct task_struct *tsk)
{
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	tsk->cputime_expires.prof_exp = 0;
	tsk->cputime_expires.virt_exp = 0;
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	tsk->cputime_expires.sched_exp = 0;
	INIT_LIST_HEAD(&tsk->cpu_timers[0]);
	INIT_LIST_HEAD(&tsk->cpu_timers[1]);
	INIT_LIST_HEAD(&tsk->cpu_timers[2]);
}
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#else
static inline void posix_cpu_timers_init(struct task_struct *tsk) { }
#endif
1542

1543 1544 1545 1546 1547 1548
static inline void
init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
{
	 task->pids[type].pid = pid;
}

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static inline void rcu_copy_process(struct task_struct *p)
{
#ifdef CONFIG_PREEMPT_RCU
	p->rcu_read_lock_nesting = 0;
	p->rcu_read_unlock_special.s = 0;
	p->rcu_blocked_node = NULL;
	INIT_LIST_HEAD(&p->rcu_node_entry);
#endif /* #ifdef CONFIG_PREEMPT_RCU */
#ifdef CONFIG_TASKS_RCU
	p->rcu_tasks_holdout = false;
	INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
	p->rcu_tasks_idle_cpu = -1;
#endif /* #ifdef CONFIG_TASKS_RCU */
}

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/*
 * This creates a new process as a copy of the old one,
 * but does not actually start it yet.
 *
 * It copies the registers, and all the appropriate
 * parts of the process environment (as per the clone
 * flags). The actual kick-off is left to the caller.
 */
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static __latent_entropy struct task_struct *copy_process(
					unsigned long clone_flags,
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					unsigned long stack_start,
					unsigned long stack_size,
					int __user *child_tidptr,
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					struct pid *pid,
1578
					int trace,
1579 1580
					unsigned long tls,
					int node)
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{
	int retval;
1583
	struct task_struct *p;
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1585 1586 1587 1588
	/*
	 * Don't allow sharing the root directory with processes in a different
	 * namespace
	 */
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	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
		return ERR_PTR(-EINVAL);

1592 1593 1594
	if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
		return ERR_PTR(-EINVAL);

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	/*
	 * Thread groups must share signals as well, and detached threads
	 * can only be started up within the thread group.
	 */
	if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
		return ERR_PTR(-EINVAL);

	/*
	 * Shared signal handlers imply shared VM. By way of the above,
	 * thread groups also imply shared VM. Blocking this case allows
	 * for various simplifications in other code.
	 */
	if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
		return ERR_PTR(-EINVAL);

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	/*
	 * Siblings of global init remain as zombies on exit since they are
	 * not reaped by their parent (swapper). To solve this and to avoid
	 * multi-rooted process trees, prevent global and container-inits
	 * from creating siblings.
	 */
	if ((clone_flags & CLONE_PARENT) &&
				current->signal->flags & SIGNAL_UNKILLABLE)
		return ERR_PTR(-EINVAL);

1620
	/*
1621
	 * If the new process will be in a different pid or user namespace
1622
	 * do not allow it to share a thread group with the forking task.
1623
	 */
1624
	if (clone_flags & CLONE_THREAD) {
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		if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
		    (task_active_pid_ns(current) !=
				current->nsproxy->pid_ns_for_children))
			return ERR_PTR(-EINVAL);
	}
1630

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1631
	retval = -ENOMEM;
1632
	p = dup_task_struct(current, node);
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	if (!p)
		goto fork_out;

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	/*
	 * This _must_ happen before we call free_task(), i.e. before we jump
	 * to any of the bad_fork_* labels. This is to avoid freeing
	 * p->set_child_tid which is (ab)used as a kthread's data pointer for
	 * kernel threads (PF_KTHREAD).
	 */
	p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
	/*
	 * Clear TID on mm_release()?
	 */
	p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;

1648 1649
	ftrace_graph_init_task(p);

1650 1651
	rt_mutex_init_task(p);

1652
#ifdef CONFIG_PROVE_LOCKING
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	DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
	DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
#endif
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	retval = -EAGAIN;
1657
	if (atomic_read(&p->real_cred->user->processes) >=
1658
			task_rlimit(p, RLIMIT_NPROC)) {
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		if (p->real_cred->user != INIT_USER &&
		    !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
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			goto bad_fork_free;
	}
1663
	current->flags &= ~PF_NPROC_EXCEEDED;
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	retval = copy_creds(p, clone_flags);
	if (retval < 0)
		goto bad_fork_free;
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	/*
	 * If multiple threads are within copy_process(), then this check
	 * triggers too late. This doesn't hurt, the check is only there
	 * to stop root fork bombs.
	 */
1674
	retval = -EAGAIN;
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	if (nr_threads >= max_threads)
		goto bad_fork_cleanup_count;

1678
	delayacct_tsk_init(p);	/* Must remain after dup_task_struct() */
1679
	p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1680
	p->flags |= PF_FORKNOEXEC;
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	INIT_LIST_HEAD(&p->children);
	INIT_LIST_HEAD(&p->sibling);
1683
	rcu_copy_process(p);
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	p->vfork_done = NULL;
	spin_lock_init(&p->alloc_lock);

	init_sigpending(&p->pending);

1689
	p->utime = p->stime = p->gtime = 0;
1690
#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1691
	p->utimescaled = p->stimescaled = 0;
1692
#endif
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	prev_cputime_init(&p->prev_cputime);

1695
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
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	seqcount_init(&p->vtime.seqcount);
	p->vtime.starttime = 0;
	p->vtime.state = VTIME_INACTIVE;
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#endif

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#if defined(SPLIT_RSS_COUNTING)
	memset(&p->rss_stat, 0, sizeof(p->rss_stat));
#endif
1704

1705 1706
	p->default_timer_slack_ns = current->timer_slack_ns;

1707
	task_io_accounting_init(&p->ioac);
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	acct_clear_integrals(p);

1710
	posix_cpu_timers_init(p);
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1712
	p->start_time = ktime_get_ns();
1713
	p->real_start_time = ktime_get_boot_ns();
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	p->io_context = NULL;
	p->audit_context = NULL;
1716
	cgroup_fork(p);
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#ifdef CONFIG_NUMA
1718
	p->mempolicy = mpol_dup(p->mempolicy);
1719 1720 1721
	if (IS_ERR(p->mempolicy)) {
		retval = PTR_ERR(p->mempolicy);
		p->mempolicy = NULL;
1722
		goto bad_fork_cleanup_threadgroup_lock;
1723
	}
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#endif
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#ifdef CONFIG_CPUSETS
	p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
	p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1728
	seqcount_init(&p->mems_allowed_seq);
1729
#endif
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#ifdef CONFIG_TRACE_IRQFLAGS
	p->irq_events = 0;
	p->hardirqs_enabled = 0;
	p->hardirq_enable_ip = 0;
	p->hardirq_enable_event = 0;
	p->hardirq_disable_ip = _THIS_IP_;
	p->hardirq_disable_event = 0;
	p->softirqs_enabled = 1;
	p->softirq_enable_ip = _THIS_IP_;
	p->softirq_enable_event = 0;
	p->softirq_disable_ip = 0;
	p->softirq_disable_event = 0;
	p->hardirq_context = 0;
	p->softirq_context = 0;
#endif
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	p->pagefault_disabled = 0;

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#ifdef CONFIG_LOCKDEP
	p->lockdep_depth = 0; /* no locks held yet */
	p->curr_chain_key = 0;
	p->lockdep_recursion = 0;
1752
	lockdep_init_task(p);
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#endif
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#ifdef CONFIG_DEBUG_MUTEXES
	p->blocked_on = NULL; /* not blocked yet */
#endif
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#ifdef CONFIG_BCACHE
	p->sequential_io	= 0;
	p->sequential_io_avg	= 0;
#endif
1762

1763
	/* Perform scheduler related setup. Assign this task to a CPU. */
1764 1765 1766
	retval = sched_fork(clone_flags, p);
	if (retval)
		goto bad_fork_cleanup_policy;
1767

1768
	retval = perf_event_init_task(p);
1769 1770
	if (retval)
		goto bad_fork_cleanup_policy;
1771 1772
	retval = audit_alloc(p);
	if (retval)
1773
		goto bad_fork_cleanup_perf;
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1774
	/* copy all the process information */
1775
	shm_init_task(p);
1776
	retval = security_task_alloc(p, clone_flags);
1777
	if (retval)
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1778
		goto bad_fork_cleanup_audit;
1779 1780 1781
	retval = copy_semundo(clone_flags, p);
	if (retval)
		goto bad_fork_cleanup_security;
1782 1783
	retval = copy_files(clone_flags, p);
	if (retval)
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1784
		goto bad_fork_cleanup_semundo;
1785 1786
	retval = copy_fs(clone_flags, p);
	if (retval)
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1787
		goto bad_fork_cleanup_files;
1788 1789
	retval = copy_sighand(clone_flags, p);
	if (retval)
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1790
		goto bad_fork_cleanup_fs;
1791 1792
	retval = copy_signal(clone_flags, p);
	if (retval)
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1793
		goto bad_fork_cleanup_sighand;
1794 1795
	retval = copy_mm(clone_flags, p);
	if (retval)
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1796
		goto bad_fork_cleanup_signal;
1797 1798
	retval = copy_namespaces(clone_flags, p);
	if (retval)
1799
		goto bad_fork_cleanup_mm;
1800 1801
	retval = copy_io(clone_flags, p);
	if (retval)
1802
		goto bad_fork_cleanup_namespaces;
1803
	retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
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1804
	if (retval)
1805
		goto bad_fork_cleanup_io;
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1806

1807
	if (pid != &init_struct_pid) {
1808
		pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1809 1810
		if (IS_ERR(pid)) {
			retval = PTR_ERR(pid);
1811
			goto bad_fork_cleanup_thread;
1812
		}
1813 1814
	}

1815 1816 1817
#ifdef CONFIG_BLOCK
	p->plug = NULL;
#endif
1818
#ifdef CONFIG_FUTEX
1819 1820 1821 1822
	p->robust_list = NULL;
#ifdef CONFIG_COMPAT
	p->compat_robust_list = NULL;
#endif
1823 1824
	INIT_LIST_HEAD(&p->pi_state_list);
	p->pi_state_cache = NULL;
1825
#endif
1826 1827 1828 1829
	/*
	 * sigaltstack should be cleared when sharing the same VM
	 */
	if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1830
		sas_ss_reset(p);
1831

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1832
	/*
1833 1834
	 * Syscall tracing and stepping should be turned off in the
	 * child regardless of CLONE_PTRACE.
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1835
	 */
1836
	user_disable_single_step(p);
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1837
	clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1838 1839 1840
#ifdef TIF_SYSCALL_EMU
	clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
#endif
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1841
	clear_all_latency_tracing(p);
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1842 1843

	/* ok, now we should be set up.. */
1844 1845
	p->pid = pid_nr(pid);
	if (clone_flags & CLONE_THREAD) {
1846
		p->exit_signal = -1;
1847 1848 1849 1850 1851 1852 1853 1854 1855 1856
		p->group_leader = current->group_leader;
		p->tgid = current->tgid;
	} else {
		if (clone_flags & CLONE_PARENT)
			p->exit_signal = current->group_leader->exit_signal;
		else
			p->exit_signal = (clone_flags & CSIGNAL);
		p->group_leader = p;
		p->tgid = p->pid;
	}
1857

1858 1859
	p->nr_dirtied = 0;
	p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1860
	p->dirty_paused_when = 0;
1861

1862
	p->pdeath_signal = 0;
1863
	INIT_LIST_HEAD(&p->thread_group);
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1864
	p->task_works = NULL;
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1865

1866
	cgroup_threadgroup_change_begin(current);
1867 1868 1869 1870 1871 1872
	/*
	 * Ensure that the cgroup subsystem policies allow the new process to be
	 * forked. It should be noted the the new process's css_set can be changed
	 * between here and cgroup_post_fork() if an organisation operation is in
	 * progress.
	 */
1873
	retval = cgroup_can_fork(p);
1874 1875 1876
	if (retval)
		goto bad_fork_free_pid;

1877 1878 1879 1880
	/*
	 * Make it visible to the rest of the system, but dont wake it up yet.
	 * Need tasklist lock for parent etc handling!
	 */
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1881 1882 1883
	write_lock_irq(&tasklist_lock);

	/* CLONE_PARENT re-uses the old parent */
1884
	if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
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1885
		p->real_parent = current->real_parent;
1886 1887
		p->parent_exec_id = current->parent_exec_id;
	} else {
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1888
		p->real_parent = current;
1889 1890
		p->parent_exec_id = current->self_exec_id;
	}
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1891

1892 1893
	klp_copy_process(p);

1894
	spin_lock(&current->sighand->siglock);
1895

1896 1897 1898 1899 1900 1901
	/*
	 * Copy seccomp details explicitly here, in case they were changed
	 * before holding sighand lock.
	 */
	copy_seccomp(p);

1902 1903
	rseq_fork(p, clone_flags);

1904 1905 1906 1907 1908 1909 1910
	/*
	 * Process group and session signals need to be delivered to just the
	 * parent before the fork or both the parent and the child after the
	 * fork. Restart if a signal comes in before we add the new process to
	 * it's process group.
	 * A fatal signal pending means that current will exit, so the new
	 * thread can't slip out of an OOM kill (or normal SIGKILL).
1911
	*/
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1912
	recalc_sigpending();
1913 1914
	if (signal_pending(current)) {
		retval = -ERESTARTNOINTR;
1915
		goto bad_fork_cancel_cgroup;
1916
	}
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1917
	if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
1918 1919 1920
		retval = -ENOMEM;
		goto bad_fork_cancel_cgroup;
	}
1921

1922
	if (likely(p->pid)) {
1923
		ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1924

1925
		init_task_pid(p, PIDTYPE_PID, pid);
1926
		if (thread_group_leader(p)) {
1927 1928 1929
			init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
			init_task_pid(p, PIDTYPE_SID, task_session(current));

1930
			if (is_child_reaper(pid)) {
1931
				ns_of_pid(pid)->child_reaper = p;
1932 1933
				p->signal->flags |= SIGNAL_UNKILLABLE;
			}
1934

1935
			p->signal->leader_pid = pid;
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1936
			p->signal->tty = tty_kref_get(current->signal->tty);
1937 1938 1939 1940 1941 1942 1943
			/*
			 * Inherit has_child_subreaper flag under the same
			 * tasklist_lock with adding child to the process tree
			 * for propagate_has_child_subreaper optimization.
			 */
			p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
							 p->real_parent->signal->is_child_subreaper;
1944
			list_add_tail(&p->sibling, &p->real_parent->children);
1945
			list_add_tail_rcu(&p->tasks, &init_task.tasks);
1946 1947
			attach_pid(p, PIDTYPE_PGID);
			attach_pid(p, PIDTYPE_SID);
1948
			__this_cpu_inc(process_counts);
1949 1950 1951 1952 1953 1954
		} else {
			current->signal->nr_threads++;
			atomic_inc(&current->signal->live);
			atomic_inc(&current->signal->sigcnt);
			list_add_tail_rcu(&p->thread_group,
					  &p->group_leader->thread_group);
1955 1956
			list_add_tail_rcu(&p->thread_node,
					  &p->signal->thread_head);
1957
		}
1958
		attach_pid(p, PIDTYPE_PID);
1959
		nr_threads++;
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1960 1961 1962
	}

	total_forks++;
1963
	spin_unlock(&current->sighand->siglock);
1964
	syscall_tracepoint_update(p);
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1965
	write_unlock_irq(&tasklist_lock);
1966

1967
	proc_fork_connector(p);
1968
	cgroup_post_fork(p);
1969
	cgroup_threadgroup_change_end(current);
1970
	perf_event_fork(p);
1971 1972

	trace_task_newtask(p, clone_flags);
1973
	uprobe_copy_process(p, clone_flags);
1974

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1975 1976
	return p;

1977
bad_fork_cancel_cgroup:
1978 1979
	spin_unlock(&current->sighand->siglock);
	write_unlock_irq(&tasklist_lock);
1980
	cgroup_cancel_fork(p);
1981
bad_fork_free_pid:
1982
	cgroup_threadgroup_change_end(current);
1983 1984
	if (pid != &init_struct_pid)
		free_pid(pid);
1985 1986
bad_fork_cleanup_thread:
	exit_thread(p);
1987
bad_fork_cleanup_io:
1988 1989
	if (p->io_context)
		exit_io_context(p);
1990
bad_fork_cleanup_namespaces:
1991
	exit_task_namespaces(p);
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1992
bad_fork_cleanup_mm:
1993
	if (p->mm)
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1994 1995
		mmput(p->mm);
bad_fork_cleanup_signal:
1996
	if (!(clone_flags & CLONE_THREAD))
1997
		free_signal_struct(p->signal);
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1998
bad_fork_cleanup_sighand:
1999
	__cleanup_sighand(p->sighand);
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2000 2001 2002 2003 2004 2005
bad_fork_cleanup_fs:
	exit_fs(p); /* blocking */
bad_fork_cleanup_files:
	exit_files(p); /* blocking */
bad_fork_cleanup_semundo:
	exit_sem(p);
2006 2007
bad_fork_cleanup_security:
	security_task_free(p);
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2008 2009
bad_fork_cleanup_audit:
	audit_free(p);
2010
bad_fork_cleanup_perf:
2011
	perf_event_free_task(p);
2012
bad_fork_cleanup_policy:
2013
	lockdep_free_task(p);
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2014
#ifdef CONFIG_NUMA
2015
	mpol_put(p->mempolicy);
2016
bad_fork_cleanup_threadgroup_lock:
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2017
#endif
2018
	delayacct_tsk_free(p);
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2019
bad_fork_cleanup_count:
2020
	atomic_dec(&p->cred->user->processes);
2021
	exit_creds(p);
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2022
bad_fork_free:
2023
	p->state = TASK_DEAD;
2024
	put_task_stack(p);
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2025
	free_task(p);
2026 2027
fork_out:
	return ERR_PTR(retval);
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2028 2029
}

2030 2031 2032 2033 2034 2035 2036 2037 2038 2039
static inline void init_idle_pids(struct pid_link *links)
{
	enum pid_type type;

	for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
		INIT_HLIST_NODE(&links[type].node); /* not really needed */
		links[type].pid = &init_struct_pid;
	}
}

2040
struct task_struct *fork_idle(int cpu)
Linus Torvalds's avatar
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2041
{
2042
	struct task_struct *task;
2043 2044
	task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
			    cpu_to_node(cpu));
2045 2046
	if (!IS_ERR(task)) {
		init_idle_pids(task->pids);
2047
		init_idle(task, cpu);
2048
	}
2049

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2050 2051 2052 2053 2054 2055 2056 2057 2058
	return task;
}

/*
 *  Ok, this is the main fork-routine.
 *
 * It copies the process, and if successful kick-starts
 * it and waits for it to finish using the VM if required.
 */
2059
long _do_fork(unsigned long clone_flags,
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2060 2061 2062
	      unsigned long stack_start,
	      unsigned long stack_size,
	      int __user *parent_tidptr,
2063 2064
	      int __user *child_tidptr,
	      unsigned long tls)
Linus Torvalds's avatar
Linus Torvalds committed
2065
{
2066 2067
	struct completion vfork;
	struct pid *pid;
Linus Torvalds's avatar
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2068 2069
	struct task_struct *p;
	int trace = 0;
2070
	long nr;
Linus Torvalds's avatar
Linus Torvalds committed
2071

Roland McGrath's avatar
Roland McGrath committed
2072
	/*
2073 2074 2075 2076
	 * Determine whether and which event to report to ptracer.  When
	 * called from kernel_thread or CLONE_UNTRACED is explicitly
	 * requested, no event is reported; otherwise, report if the event
	 * for the type of forking is enabled.
Roland McGrath's avatar
Roland McGrath committed
2077
	 */
2078
	if (!(clone_flags & CLONE_UNTRACED)) {
2079 2080 2081 2082 2083 2084 2085 2086 2087 2088
		if (clone_flags & CLONE_VFORK)
			trace = PTRACE_EVENT_VFORK;
		else if ((clone_flags & CSIGNAL) != SIGCHLD)
			trace = PTRACE_EVENT_CLONE;
		else
			trace = PTRACE_EVENT_FORK;

		if (likely(!ptrace_event_enabled(current, trace)))
			trace = 0;
	}
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2089

Al Viro's avatar
Al Viro committed
2090
	p = copy_process(clone_flags, stack_start, stack_size,
2091
			 child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
2092
	add_latent_entropy();
2093 2094 2095 2096

	if (IS_ERR(p))
		return PTR_ERR(p);

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2097 2098 2099 2100
	/*
	 * Do this prior waking up the new thread - the thread pointer
	 * might get invalid after that point, if the thread exits quickly.
	 */
2101
	trace_sched_process_fork(current, p);
2102

2103 2104
	pid = get_task_pid(p, PIDTYPE_PID);
	nr = pid_vnr(pid);
2105

2106 2107
	if (clone_flags & CLONE_PARENT_SETTID)
		put_user(nr, parent_tidptr);
2108

2109 2110 2111 2112 2113
	if (clone_flags & CLONE_VFORK) {
		p->vfork_done = &vfork;
		init_completion(&vfork);
		get_task_struct(p);
	}
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2114

2115
	wake_up_new_task(p);
Roland McGrath's avatar
Roland McGrath committed
2116

2117 2118 2119
	/* forking complete and child started to run, tell ptracer */
	if (unlikely(trace))
		ptrace_event_pid(trace, pid);
2120

2121 2122 2123
	if (clone_flags & CLONE_VFORK) {
		if (!wait_for_vfork_done(p, &vfork))
			ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
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2124
	}
2125 2126

	put_pid(pid);
2127
	return nr;
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2128 2129
}

2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143
#ifndef CONFIG_HAVE_COPY_THREAD_TLS
/* For compatibility with architectures that call do_fork directly rather than
 * using the syscall entry points below. */
long do_fork(unsigned long clone_flags,
	      unsigned long stack_start,
	      unsigned long stack_size,
	      int __user *parent_tidptr,
	      int __user *child_tidptr)
{
	return _do_fork(clone_flags, stack_start, stack_size,
			parent_tidptr, child_tidptr, 0);
}
#endif

2144 2145 2146 2147 2148
/*
 * Create a kernel thread.
 */
pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
{
2149 2150
	return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
		(unsigned long)arg, NULL, NULL, 0);
2151 2152
}

2153 2154 2155 2156
#ifdef __ARCH_WANT_SYS_FORK
SYSCALL_DEFINE0(fork)
{
#ifdef CONFIG_MMU
2157
	return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
2158 2159
#else
	/* can not support in nommu mode */
2160
	return -EINVAL;
2161 2162 2163 2164 2165 2166 2167
#endif
}
#endif

#ifdef __ARCH_WANT_SYS_VFORK
SYSCALL_DEFINE0(vfork)
{
2168 2169
	return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
			0, NULL, NULL, 0);
2170 2171 2172 2173 2174 2175 2176
}
#endif

#ifdef __ARCH_WANT_SYS_CLONE
#ifdef CONFIG_CLONE_BACKWARDS
SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
		 int __user *, parent_tidptr,
2177
		 unsigned long, tls,
2178 2179 2180 2181 2182
		 int __user *, child_tidptr)
#elif defined(CONFIG_CLONE_BACKWARDS2)
SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
		 int __user *, parent_tidptr,
		 int __user *, child_tidptr,
2183
		 unsigned long, tls)
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Michal Simek committed
2184 2185 2186 2187 2188
#elif defined(CONFIG_CLONE_BACKWARDS3)
SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
		int, stack_size,
		int __user *, parent_tidptr,
		int __user *, child_tidptr,
2189
		unsigned long, tls)
2190 2191 2192 2193
#else
SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
		 int __user *, parent_tidptr,
		 int __user *, child_tidptr,
2194
		 unsigned long, tls)
2195 2196
#endif
{
2197
	return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
2198 2199 2200
}
#endif

2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232
void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
{
	struct task_struct *leader, *parent, *child;
	int res;

	read_lock(&tasklist_lock);
	leader = top = top->group_leader;
down:
	for_each_thread(leader, parent) {
		list_for_each_entry(child, &parent->children, sibling) {
			res = visitor(child, data);
			if (res) {
				if (res < 0)
					goto out;
				leader = child;
				goto down;
			}
up:
			;
		}
	}

	if (leader != top) {
		child = leader;
		parent = child->real_parent;
		leader = parent->group_leader;
		goto up;
	}
out:
	read_unlock(&tasklist_lock);
}

2233 2234 2235 2236
#ifndef ARCH_MIN_MMSTRUCT_ALIGN
#define ARCH_MIN_MMSTRUCT_ALIGN 0
#endif

2237
static void sighand_ctor(void *data)
2238 2239 2240
{
	struct sighand_struct *sighand = data;

2241
	spin_lock_init(&sighand->siglock);
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Davide Libenzi committed
2242
	init_waitqueue_head(&sighand->signalfd_wqh);
2243 2244
}

Linus Torvalds's avatar
Linus Torvalds committed
2245 2246 2247 2248
void __init proc_caches_init(void)
{
	sighand_cachep = kmem_cache_create("sighand_cache",
			sizeof(struct sighand_struct), 0,
2249
			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2250
			SLAB_ACCOUNT, sighand_ctor);
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Linus Torvalds committed
2251 2252
	signal_cachep = kmem_cache_create("signal_cache",
			sizeof(struct signal_struct), 0,
2253
			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2254
			NULL);
2255
	files_cachep = kmem_cache_create("files_cache",
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Linus Torvalds committed
2256
			sizeof(struct files_struct), 0,
2257
			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2258
			NULL);
2259
	fs_cachep = kmem_cache_create("fs_cache",
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Linus Torvalds committed
2260
			sizeof(struct fs_struct), 0,
2261
			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2262
			NULL);
2263 2264 2265 2266 2267 2268 2269
	/*
	 * FIXME! The "sizeof(struct mm_struct)" currently includes the
	 * whole struct cpumask for the OFFSTACK case. We could change
	 * this to *only* allocate as much of it as required by the
	 * maximum number of CPU's we can ever have.  The cpumask_allocation
	 * is at the end of the structure, exactly for that reason.
	 */
2270
	mm_cachep = kmem_cache_create_usercopy("mm_struct",
2271
			sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
2272
			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2273 2274
			offsetof(struct mm_struct, saved_auxv),
			sizeof_field(struct mm_struct, saved_auxv),
2275 2276
			NULL);
	vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2277
	mmap_init();
2278
	nsproxy_cache_init();
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}
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/*
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 * Check constraints on flags passed to the unshare system call.
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 */
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static int check_unshare_flags(unsigned long unshare_flags)
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{
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	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
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				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
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				CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
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		return -EINVAL;
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	/*
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	 * Not implemented, but pretend it works if there is nothing
	 * to unshare.  Note that unsharing the address space or the
	 * signal handlers also need to unshare the signal queues (aka
	 * CLONE_THREAD).
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	 */
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	if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
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		if (!thread_group_empty(current))
			return -EINVAL;
	}
	if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
		if (atomic_read(&current->sighand->count) > 1)
			return -EINVAL;
	}
	if (unshare_flags & CLONE_VM) {
		if (!current_is_single_threaded())
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			return -EINVAL;
	}
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	return 0;
}

/*
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 * Unshare the filesystem structure if it is being shared
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 */
static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
{
	struct fs_struct *fs = current->fs;

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	if (!(unshare_flags & CLONE_FS) || !fs)
		return 0;

	/* don't need lock here; in the worst case we'll do useless copy */
	if (fs->users == 1)
		return 0;

	*new_fsp = copy_fs_struct(fs);
	if (!*new_fsp)
		return -ENOMEM;
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	return 0;
}

/*
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 * Unshare file descriptor table if it is being shared
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 */
static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
{
	struct files_struct *fd = current->files;
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	int error = 0;
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	if ((unshare_flags & CLONE_FILES) &&
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	    (fd && atomic_read(&fd->count) > 1)) {
		*new_fdp = dup_fd(fd, &error);
		if (!*new_fdp)
			return error;
	}
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	return 0;
}

/*
 * unshare allows a process to 'unshare' part of the process
 * context which was originally shared using clone.  copy_*
 * functions used by do_fork() cannot be used here directly
 * because they modify an inactive task_struct that is being
 * constructed. Here we are modifying the current, active,
 * task_struct.
 */
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int ksys_unshare(unsigned long unshare_flags)
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{
	struct fs_struct *fs, *new_fs = NULL;
	struct files_struct *fd, *new_fd = NULL;
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	struct cred *new_cred = NULL;
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	struct nsproxy *new_nsproxy = NULL;
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	int do_sysvsem = 0;
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	int err;
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	/*
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	 * If unsharing a user namespace must also unshare the thread group
	 * and unshare the filesystem root and working directories.
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	 */
	if (unshare_flags & CLONE_NEWUSER)
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		unshare_flags |= CLONE_THREAD | CLONE_FS;
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	/*
	 * If unsharing vm, must also unshare signal handlers.
	 */
	if (unshare_flags & CLONE_VM)
		unshare_flags |= CLONE_SIGHAND;
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	/*
	 * If unsharing a signal handlers, must also unshare the signal queues.
	 */
	if (unshare_flags & CLONE_SIGHAND)
		unshare_flags |= CLONE_THREAD;
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	/*
	 * If unsharing namespace, must also unshare filesystem information.
	 */
	if (unshare_flags & CLONE_NEWNS)
		unshare_flags |= CLONE_FS;
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	err = check_unshare_flags(unshare_flags);
	if (err)
		goto bad_unshare_out;
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	/*
	 * CLONE_NEWIPC must also detach from the undolist: after switching
	 * to a new ipc namespace, the semaphore arrays from the old
	 * namespace are unreachable.
	 */
	if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
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		do_sysvsem = 1;
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	err = unshare_fs(unshare_flags, &new_fs);
	if (err)
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		goto bad_unshare_out;
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	err = unshare_fd(unshare_flags, &new_fd);
	if (err)
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		goto bad_unshare_cleanup_fs;
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	err = unshare_userns(unshare_flags, &new_cred);
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	if (err)
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		goto bad_unshare_cleanup_fd;
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	err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
					 new_cred, new_fs);
	if (err)
		goto bad_unshare_cleanup_cred;
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	if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
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		if (do_sysvsem) {
			/*
			 * CLONE_SYSVSEM is equivalent to sys_exit().
			 */
			exit_sem(current);
		}
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		if (unshare_flags & CLONE_NEWIPC) {
			/* Orphan segments in old ns (see sem above). */
			exit_shm(current);
			shm_init_task(current);
		}
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		if (new_nsproxy)
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			switch_task_namespaces(current, new_nsproxy);
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		task_lock(current);

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		if (new_fs) {
			fs = current->fs;
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			spin_lock(&fs->lock);
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			current->fs = new_fs;
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			if (--fs->users)
				new_fs = NULL;
			else
				new_fs = fs;
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			spin_unlock(&fs->lock);
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		}

		if (new_fd) {
			fd = current->files;
			current->files = new_fd;
			new_fd = fd;
		}

		task_unlock(current);
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		if (new_cred) {
			/* Install the new user namespace */
			commit_creds(new_cred);
			new_cred = NULL;
		}
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	}

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	perf_event_namespaces(current);

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bad_unshare_cleanup_cred:
	if (new_cred)
		put_cred(new_cred);
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bad_unshare_cleanup_fd:
	if (new_fd)
		put_files_struct(new_fd);

bad_unshare_cleanup_fs:
	if (new_fs)
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		free_fs_struct(new_fs);
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bad_unshare_out:
	return err;
}
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SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
{
	return ksys_unshare(unshare_flags);
}

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/*
 *	Helper to unshare the files of the current task.
 *	We don't want to expose copy_files internals to
 *	the exec layer of the kernel.
 */

int unshare_files(struct files_struct **displaced)
{
	struct task_struct *task = current;
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	struct files_struct *copy = NULL;
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	int error;

	error = unshare_fd(CLONE_FILES, &copy);
	if (error || !copy) {
		*displaced = NULL;
		return error;
	}
	*displaced = task->files;
	task_lock(task);
	task->files = copy;
	task_unlock(task);
	return 0;
}
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int sysctl_max_threads(struct ctl_table *table, int write,
		       void __user *buffer, size_t *lenp, loff_t *ppos)
{
	struct ctl_table t;
	int ret;
	int threads = max_threads;
	int min = MIN_THREADS;
	int max = MAX_THREADS;

	t = *table;
	t.data = &threads;
	t.extra1 = &min;
	t.extra2 = &max;

	ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
	if (ret || !write)
		return ret;

	set_max_threads(threads);

	return 0;
}