fork.c 41.1 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>
#include <linux/init.h>
#include <linux/unistd.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/completion.h>
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#include <linux/mnt_namespace.h>
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#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/fs.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/swap.h>
#include <linux/syscalls.h>
#include <linux/jiffies.h>
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#include <linux/tracehook.h>
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#include <linux/futex.h>
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#include <linux/compat.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/profile.h>
#include <linux/rmap.h>
#include <linux/acct.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/proc_fs.h>
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#include <linux/blkdev.h>
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#include <trace/sched.h>
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#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>

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

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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DEFINE_TRACE(sched_process_fork);

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int nr_processes(void)
{
	int cpu;
	int total = 0;

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

	return total;
}

#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
# define alloc_task_struct()	kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
# define free_task_struct(tsk)	kmem_cache_free(task_struct_cachep, (tsk))
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static struct kmem_cache *task_struct_cachep;
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#endif

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#ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
{
#ifdef CONFIG_DEBUG_STACK_USAGE
	gfp_t mask = GFP_KERNEL | __GFP_ZERO;
#else
	gfp_t mask = GFP_KERNEL;
#endif
	return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
}

static inline void free_thread_info(struct thread_info *ti)
{
	free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
}
#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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void free_task(struct task_struct *tsk)
{
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	prop_local_destroy_single(&tsk->dirties);
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	free_thread_info(tsk->stack);
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	rt_mutex_debug_task_free(tsk);
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	ftrace_retfunc_exit_task(tsk);
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	free_task_struct(tsk);
}
EXPORT_SYMBOL(free_task);

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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);

	security_task_free(tsk);
	free_uid(tsk->user);
	put_group_info(tsk->group_info);
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	delayacct_tsk_free(tsk);
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	if (!profile_handoff_task(tsk))
		free_task(tsk);
}

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/*
 * macro override instead of weak attribute alias, to workaround
 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
 */
#ifndef arch_task_cache_init
#define arch_task_cache_init()
#endif
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void __init fork_init(unsigned long mempages)
{
#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
#ifndef ARCH_MIN_TASKALIGN
#define ARCH_MIN_TASKALIGN	L1_CACHE_BYTES
#endif
	/* create a slab on which task_structs can be allocated */
	task_struct_cachep =
		kmem_cache_create("task_struct", sizeof(struct task_struct),
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			ARCH_MIN_TASKALIGN, SLAB_PANIC, 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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	/*
	 * The default maximum number of threads is set to a safe
	 * value: the thread structures can take up at most half
	 * of memory.
	 */
	max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);

	/*
	 * we need to allow at least 20 threads to boot a system
	 */
	if(max_threads < 20)
		max_threads = 20;

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

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static struct task_struct *dup_task_struct(struct task_struct *orig)
{
	struct task_struct *tsk;
	struct thread_info *ti;
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	int err;
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	prepare_to_copy(orig);

	tsk = alloc_task_struct();
	if (!tsk)
		return NULL;

	ti = alloc_thread_info(tsk);
	if (!ti) {
		free_task_struct(tsk);
		return NULL;
	}

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 	err = arch_dup_task_struct(tsk, orig);
	if (err)
		goto out;

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	tsk->stack = ti;
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	err = prop_local_init_single(&tsk->dirties);
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	if (err)
		goto out;
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	setup_thread_stack(tsk, orig);
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#ifdef CONFIG_CC_STACKPROTECTOR
	tsk->stack_canary = get_random_int();
#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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	atomic_set(&tsk->fs_excl, 0);
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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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	return tsk;
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out:
	free_thread_info(ti);
	free_task_struct(tsk);
	return NULL;
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}

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

	down_write(&oldmm->mmap_sem);
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	flush_cache_dup_mm(oldmm);
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	/*
	 * Not linked in yet - no deadlock potential:
	 */
	down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
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	mm->locked_vm = 0;
	mm->mmap = NULL;
	mm->mmap_cache = NULL;
	mm->free_area_cache = oldmm->mmap_base;
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	mm->cached_hole_size = ~0UL;
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	mm->map_count = 0;
	cpus_clear(mm->cpu_vm_mask);
	mm->mm_rb = RB_ROOT;
	rb_link = &mm->mm_rb.rb_node;
	rb_parent = NULL;
	pprev = &mm->mmap;

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

		if (mpnt->vm_flags & VM_DONTCOPY) {
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			long pages = vma_pages(mpnt);
			mm->total_vm -= pages;
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			vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
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								-pages);
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			continue;
		}
		charge = 0;
		if (mpnt->vm_flags & VM_ACCOUNT) {
			unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
			if (security_vm_enough_memory(len))
				goto fail_nomem;
			charge = len;
		}
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		tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
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		if (!tmp)
			goto fail_nomem;
		*tmp = *mpnt;
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		pol = mpol_dup(vma_policy(mpnt));
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		retval = PTR_ERR(pol);
		if (IS_ERR(pol))
			goto fail_nomem_policy;
		vma_set_policy(tmp, pol);
		tmp->vm_flags &= ~VM_LOCKED;
		tmp->vm_mm = mm;
		tmp->vm_next = NULL;
		anon_vma_link(tmp);
		file = tmp->vm_file;
		if (file) {
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			struct inode *inode = file->f_path.dentry->d_inode;
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			get_file(file);
			if (tmp->vm_flags & VM_DENYWRITE)
				atomic_dec(&inode->i_writecount);
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			/* insert tmp into the share list, just after mpnt */
			spin_lock(&file->f_mapping->i_mmap_lock);
			tmp->vm_truncate_count = mpnt->vm_truncate_count;
			flush_dcache_mmap_lock(file->f_mapping);
			vma_prio_tree_add(tmp, mpnt);
			flush_dcache_mmap_unlock(file->f_mapping);
			spin_unlock(&file->f_mapping->i_mmap_lock);
		}

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		/*
		 * 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);

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

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

		mm->map_count++;
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		retval = copy_page_range(mm, oldmm, mpnt);
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		if (tmp->vm_ops && tmp->vm_ops->open)
			tmp->vm_ops->open(tmp);

		if (retval)
			goto out;
	}
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	/* a new mm has just been created */
	arch_dup_mmap(oldmm, mm);
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	retval = 0;
out:
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	up_write(&mm->mmap_sem);
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	flush_tlb_mm(oldmm);
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	up_write(&oldmm->mmap_sem);
	return retval;
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)
{
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	pgd_free(mm, mm->pgd);
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}
#else
#define dup_mmap(mm, oldmm)	(0)
#define mm_alloc_pgd(mm)	(0)
#define mm_free_pgd(mm)
#endif /* CONFIG_MMU */

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__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
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#define allocate_mm()	(kmem_cache_alloc(mm_cachep, GFP_KERNEL))
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#define free_mm(mm)	(kmem_cache_free(mm_cachep, (mm)))

#include <linux/init_task.h>

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static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
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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->flags = (current->mm) ? current->mm->flags
				  : MMF_DUMP_FILTER_DEFAULT;
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	mm->core_state = NULL;
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	mm->nr_ptes = 0;
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	set_mm_counter(mm, file_rss, 0);
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	set_mm_counter(mm, anon_rss, 0);
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	spin_lock_init(&mm->page_table_lock);
	rwlock_init(&mm->ioctx_list_lock);
	mm->ioctx_list = NULL;
	mm->free_area_cache = TASK_UNMAPPED_BASE;
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	mm->cached_hole_size = ~0UL;
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	mm_init_owner(mm, p);
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	if (likely(!mm_alloc_pgd(mm))) {
		mm->def_flags = 0;
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		mmu_notifier_mm_init(mm);
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		return mm;
	}
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	free_mm(mm);
	return NULL;
}

/*
 * Allocate and initialize an mm_struct.
 */
struct mm_struct * mm_alloc(void)
{
	struct mm_struct * mm;

	mm = allocate_mm();
	if (mm) {
		memset(mm, 0, sizeof(*mm));
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		mm = mm_init(mm, current);
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	}
	return 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);
	mm_free_pgd(mm);
	destroy_context(mm);
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	mmu_notifier_mm_destroy(mm);
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	free_mm(mm);
}
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EXPORT_SYMBOL_GPL(__mmdrop);
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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)) {
		exit_aio(mm);
		exit_mmap(mm);
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		set_mm_exe_file(mm, NULL);
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		if (!list_empty(&mm->mmlist)) {
			spin_lock(&mmlist_lock);
			list_del(&mm->mmlist);
			spin_unlock(&mmlist_lock);
		}
		put_swap_token(mm);
		mmdrop(mm);
	}
}
EXPORT_SYMBOL_GPL(mmput);

/**
 * 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
			atomic_inc(&mm->mm_users);
	}
	task_unlock(task);
	return mm;
}
EXPORT_SYMBOL_GPL(get_task_mm);

/* 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)
{
	struct completion *vfork_done = tsk->vfork_done;

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	/* Get rid of any futexes when releasing the mm */
#ifdef CONFIG_FUTEX
	if (unlikely(tsk->robust_list))
		exit_robust_list(tsk);
#ifdef CONFIG_COMPAT
	if (unlikely(tsk->compat_robust_list))
		compat_exit_robust_list(tsk);
#endif
#endif

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

	/* notify parent sleeping on vfork() */
	if (vfork_done) {
		tsk->vfork_done = NULL;
		complete(vfork_done);
	}
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	/*
	 * If we're exiting normally, clear a user-space tid field if
	 * requested.  We leave this alone when dying by signal, to leave
	 * the value intact in a core dump, and to save the unnecessary
	 * trouble otherwise.  Userland only wants this done for a sys_exit.
	 */
	if (tsk->clear_child_tid
	    && !(tsk->flags & PF_SIGNALED)
	    && atomic_read(&mm->mm_users) > 1) {
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		u32 __user * tidptr = tsk->clear_child_tid;
		tsk->clear_child_tid = NULL;

		/*
		 * We don't check the error code - if userspace has
		 * not set up a proper pointer then tough luck.
		 */
		put_user(0, tidptr);
		sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
	}
}

567 568 569 570
/*
 * Allocate a new mm structure and copy contents from the
 * mm structure of the passed in task structure.
 */
571
struct mm_struct *dup_mm(struct task_struct *tsk)
572 573 574 575 576 577 578 579 580 581 582 583 584
{
	struct mm_struct *mm, *oldmm = current->mm;
	int err;

	if (!oldmm)
		return NULL;

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

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

585 586 587 588
	/* Initializing for Swap token stuff */
	mm->token_priority = 0;
	mm->last_interval = 0;

589
	if (!mm_init(mm, tsk))
590 591 592 593 594
		goto fail_nomem;

	if (init_new_context(tsk, mm))
		goto fail_nocontext;

M
Matt Helsley 已提交
595 596
	dup_mm_exe_file(oldmm, mm);

597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621
	err = dup_mmap(mm, oldmm);
	if (err)
		goto free_pt;

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

	return mm;

free_pt:
	mmput(mm);

fail_nomem:
	return NULL;

fail_nocontext:
	/*
	 * If init_new_context() failed, we cannot use mmput() to free the mm
	 * because it calls destroy_context()
	 */
	mm_free_pgd(mm);
	free_mm(mm);
	return NULL;
}

L
Linus Torvalds 已提交
622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648
static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
{
	struct mm_struct * mm, *oldmm;
	int retval;

	tsk->min_flt = tsk->maj_flt = 0;
	tsk->nvcsw = tsk->nivcsw = 0;

	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;

	if (clone_flags & CLONE_VM) {
		atomic_inc(&oldmm->mm_users);
		mm = oldmm;
		goto good_mm;
	}

	retval = -ENOMEM;
649
	mm = dup_mm(tsk);
L
Linus Torvalds 已提交
650 651 652 653
	if (!mm)
		goto fail_nomem;

good_mm:
654 655 656 657
	/* Initializing for Swap token stuff */
	mm->token_priority = 0;
	mm->last_interval = 0;

L
Linus Torvalds 已提交
658 659 660 661 662 663 664 665
	tsk->mm = mm;
	tsk->active_mm = mm;
	return 0;

fail_nomem:
	return retval;
}

A
Alexey Dobriyan 已提交
666
static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
L
Linus Torvalds 已提交
667 668 669 670 671 672 673 674
{
	struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
	/* We don't need to lock fs - think why ;-) */
	if (fs) {
		atomic_set(&fs->count, 1);
		rwlock_init(&fs->lock);
		fs->umask = old->umask;
		read_lock(&old->lock);
J
Jan Blunck 已提交
675 676 677 678
		fs->root = old->root;
		path_get(&old->root);
		fs->pwd = old->pwd;
		path_get(&old->pwd);
L
Linus Torvalds 已提交
679 680 681 682 683 684 685 686 687 688 689 690
		read_unlock(&old->lock);
	}
	return fs;
}

struct fs_struct *copy_fs_struct(struct fs_struct *old)
{
	return __copy_fs_struct(old);
}

EXPORT_SYMBOL_GPL(copy_fs_struct);

A
Alexey Dobriyan 已提交
691
static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
L
Linus Torvalds 已提交
692 693 694 695 696 697 698 699 700 701 702
{
	if (clone_flags & CLONE_FS) {
		atomic_inc(&current->fs->count);
		return 0;
	}
	tsk->fs = __copy_fs_struct(current->fs);
	if (!tsk->fs)
		return -ENOMEM;
	return 0;
}

703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729
static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
{
	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;
}

730
static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
731 732 733 734 735 736
{
#ifdef CONFIG_BLOCK
	struct io_context *ioc = current->io_context;

	if (!ioc)
		return 0;
737 738 739 740 741 742 743 744
	/*
	 * Share io context with parent, if CLONE_IO is set
	 */
	if (clone_flags & CLONE_IO) {
		tsk->io_context = ioc_task_link(ioc);
		if (unlikely(!tsk->io_context))
			return -ENOMEM;
	} else if (ioprio_valid(ioc->ioprio)) {
745 746 747 748 749 750 751 752 753 754
		tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
		if (unlikely(!tsk->io_context))
			return -ENOMEM;

		tsk->io_context->ioprio = ioc->ioprio;
	}
#endif
	return 0;
}

A
Alexey Dobriyan 已提交
755
static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
L
Linus Torvalds 已提交
756 757 758 759 760 761 762 763
{
	struct sighand_struct *sig;

	if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
		atomic_inc(&current->sighand->count);
		return 0;
	}
	sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
I
Ingo Molnar 已提交
764
	rcu_assign_pointer(tsk->sighand, sig);
L
Linus Torvalds 已提交
765 766 767 768 769 770 771
	if (!sig)
		return -ENOMEM;
	atomic_set(&sig->count, 1);
	memcpy(sig->action, current->sighand->action, sizeof(sig->action));
	return 0;
}

772
void __cleanup_sighand(struct sighand_struct *sighand)
773 774 775 776 777
{
	if (atomic_dec_and_test(&sighand->count))
		kmem_cache_free(sighand_cachep, sighand);
}

778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803

/*
 * Initialize POSIX timer handling for a thread group.
 */
static void posix_cpu_timers_init_group(struct signal_struct *sig)
{
	/* Thread group counters. */
	thread_group_cputime_init(sig);

	/* Expiration times and increments. */
	sig->it_virt_expires = cputime_zero;
	sig->it_virt_incr = cputime_zero;
	sig->it_prof_expires = cputime_zero;
	sig->it_prof_incr = cputime_zero;

	/* Cached expiration times. */
	sig->cputime_expires.prof_exp = cputime_zero;
	sig->cputime_expires.virt_exp = cputime_zero;
	sig->cputime_expires.sched_exp = 0;

	/* The timer lists. */
	INIT_LIST_HEAD(&sig->cpu_timers[0]);
	INIT_LIST_HEAD(&sig->cpu_timers[1]);
	INIT_LIST_HEAD(&sig->cpu_timers[2]);
}

A
Alexey Dobriyan 已提交
804
static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
L
Linus Torvalds 已提交
805 806 807 808 809
{
	struct signal_struct *sig;
	int ret;

	if (clone_flags & CLONE_THREAD) {
810
		ret = thread_group_cputime_clone_thread(current);
811 812 813 814 815
		if (likely(!ret)) {
			atomic_inc(&current->signal->count);
			atomic_inc(&current->signal->live);
		}
		return ret;
L
Linus Torvalds 已提交
816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834
	}
	sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
	tsk->signal = sig;
	if (!sig)
		return -ENOMEM;

	ret = copy_thread_group_keys(tsk);
	if (ret < 0) {
		kmem_cache_free(signal_cachep, sig);
		return ret;
	}

	atomic_set(&sig->count, 1);
	atomic_set(&sig->live, 1);
	init_waitqueue_head(&sig->wait_chldexit);
	sig->flags = 0;
	sig->group_exit_code = 0;
	sig->group_exit_task = NULL;
	sig->group_stop_count = 0;
835
	sig->curr_target = tsk;
L
Linus Torvalds 已提交
836 837 838
	init_sigpending(&sig->shared_pending);
	INIT_LIST_HEAD(&sig->posix_timers);

839
	hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
840
	sig->it_real_incr.tv64 = 0;
L
Linus Torvalds 已提交
841 842 843
	sig->real_timer.function = it_real_fn;

	sig->leader = 0;	/* session leadership doesn't inherit */
844
	sig->tty_old_pgrp = NULL;
A
Alan Cox 已提交
845
	sig->tty = NULL;
L
Linus Torvalds 已提交
846

847
	sig->cutime = sig->cstime = cputime_zero;
848 849
	sig->gtime = cputime_zero;
	sig->cgtime = cputime_zero;
L
Linus Torvalds 已提交
850 851
	sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
	sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
852
	sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
853
	task_io_accounting_init(&sig->ioac);
854
	taskstats_tgid_init(sig);
L
Linus Torvalds 已提交
855 856 857 858 859

	task_lock(current->group_leader);
	memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
	task_unlock(current->group_leader);

860 861
	posix_cpu_timers_init_group(sig);

862
	acct_init_pacct(&sig->pacct);
L
Linus Torvalds 已提交
863

M
Miloslav Trmac 已提交
864 865
	tty_audit_fork(sig);

L
Linus Torvalds 已提交
866 867 868
	return 0;
}

869 870
void __cleanup_signal(struct signal_struct *sig)
{
871
	thread_group_cputime_free(sig);
872
	exit_thread_group_keys(sig);
A
Alan Cox 已提交
873
	tty_kref_put(sig->tty);
874 875 876
	kmem_cache_free(signal_cachep, sig);
}

A
Alexey Dobriyan 已提交
877
static void cleanup_signal(struct task_struct *tsk)
878 879 880 881 882 883 884 885 886
{
	struct signal_struct *sig = tsk->signal;

	atomic_dec(&sig->live);

	if (atomic_dec_and_test(&sig->count))
		__cleanup_signal(sig);
}

A
Alexey Dobriyan 已提交
887
static void copy_flags(unsigned long clone_flags, struct task_struct *p)
L
Linus Torvalds 已提交
888 889 890
{
	unsigned long new_flags = p->flags;

891
	new_flags &= ~PF_SUPERPRIV;
L
Linus Torvalds 已提交
892
	new_flags |= PF_FORKNOEXEC;
R
Roland McGrath 已提交
893
	new_flags |= PF_STARTING;
L
Linus Torvalds 已提交
894
	p->flags = new_flags;
895
	clear_freeze_flag(p);
L
Linus Torvalds 已提交
896 897 898 899 900 901
}

asmlinkage long sys_set_tid_address(int __user *tidptr)
{
	current->clear_child_tid = tidptr;

902
	return task_pid_vnr(current);
L
Linus Torvalds 已提交
903 904
}

A
Alexey Dobriyan 已提交
905
static void rt_mutex_init_task(struct task_struct *p)
I
Ingo Molnar 已提交
906 907
{
	spin_lock_init(&p->pi_lock);
908
#ifdef CONFIG_RT_MUTEXES
I
Ingo Molnar 已提交
909 910 911 912 913
	plist_head_init(&p->pi_waiters, &p->pi_lock);
	p->pi_blocked_on = NULL;
#endif
}

914 915 916 917 918 919 920
#ifdef CONFIG_MM_OWNER
void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
{
	mm->owner = p;
}
#endif /* CONFIG_MM_OWNER */

921 922 923 924 925 926 927 928 929 930 931 932 933
/*
 * Initialize POSIX timer handling for a single task.
 */
static void posix_cpu_timers_init(struct task_struct *tsk)
{
	tsk->cputime_expires.prof_exp = cputime_zero;
	tsk->cputime_expires.virt_exp = cputime_zero;
	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]);
}

L
Linus Torvalds 已提交
934 935 936 937 938 939 940 941
/*
 * 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.
 */
942 943 944 945 946
static struct task_struct *copy_process(unsigned long clone_flags,
					unsigned long stack_start,
					struct pt_regs *regs,
					unsigned long stack_size,
					int __user *child_tidptr,
R
Roland McGrath 已提交
947 948
					struct pid *pid,
					int trace)
L
Linus Torvalds 已提交
949 950
{
	int retval;
951
	struct task_struct *p;
952
	int cgroup_callbacks_done = 0;
L
Linus Torvalds 已提交
953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980

	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
		return ERR_PTR(-EINVAL);

	/*
	 * 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);

	retval = security_task_create(clone_flags);
	if (retval)
		goto fork_out;

	retval = -ENOMEM;
	p = dup_task_struct(current);
	if (!p)
		goto fork_out;

981 982
	rt_mutex_init_task(p);

I
Ingo Molnar 已提交
983
#ifdef CONFIG_PROVE_LOCKING
984 985 986
	DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
	DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
#endif
L
Linus Torvalds 已提交
987 988 989 990
	retval = -EAGAIN;
	if (atomic_read(&p->user->processes) >=
			p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
		if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
991
		    p->user != current->nsproxy->user_ns->root_user)
L
Linus Torvalds 已提交
992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006
			goto bad_fork_free;
	}

	atomic_inc(&p->user->__count);
	atomic_inc(&p->user->processes);
	get_group_info(p->group_info);

	/*
	 * 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.
	 */
	if (nr_threads >= max_threads)
		goto bad_fork_cleanup_count;

A
Al Viro 已提交
1007
	if (!try_module_get(task_thread_info(p)->exec_domain->module))
L
Linus Torvalds 已提交
1008 1009 1010 1011 1012 1013
		goto bad_fork_cleanup_count;

	if (p->binfmt && !try_module_get(p->binfmt->module))
		goto bad_fork_cleanup_put_domain;

	p->did_exec = 0;
1014
	delayacct_tsk_init(p);	/* Must remain after dup_task_struct() */
L
Linus Torvalds 已提交
1015 1016 1017
	copy_flags(clone_flags, p);
	INIT_LIST_HEAD(&p->children);
	INIT_LIST_HEAD(&p->sibling);
P
Paul E. McKenney 已提交
1018 1019 1020 1021
#ifdef CONFIG_PREEMPT_RCU
	p->rcu_read_lock_nesting = 0;
	p->rcu_flipctr_idx = 0;
#endif /* #ifdef CONFIG_PREEMPT_RCU */
L
Linus Torvalds 已提交
1022 1023 1024 1025 1026 1027 1028 1029
	p->vfork_done = NULL;
	spin_lock_init(&p->alloc_lock);

	clear_tsk_thread_flag(p, TIF_SIGPENDING);
	init_sigpending(&p->pending);

	p->utime = cputime_zero;
	p->stime = cputime_zero;
1030
	p->gtime = cputime_zero;
1031 1032
	p->utimescaled = cputime_zero;
	p->stimescaled = cputime_zero;
P
Peter Zijlstra 已提交
1033
	p->prev_utime = cputime_zero;
1034
	p->prev_stime = cputime_zero;
1035

1036 1037
	p->default_timer_slack_ns = current->timer_slack_ns;

1038 1039 1040 1041 1042
#ifdef CONFIG_DETECT_SOFTLOCKUP
	p->last_switch_count = 0;
	p->last_switch_timestamp = 0;
#endif

1043
	task_io_accounting_init(&p->ioac);
L
Linus Torvalds 已提交
1044 1045
	acct_clear_integrals(p);

1046
	posix_cpu_timers_init(p);
L
Linus Torvalds 已提交
1047 1048 1049

	p->lock_depth = -1;		/* -1 = no lock */
	do_posix_clock_monotonic_gettime(&p->start_time);
1050 1051
	p->real_start_time = p->start_time;
	monotonic_to_bootbased(&p->real_start_time);
1052
#ifdef CONFIG_SECURITY
L
Linus Torvalds 已提交
1053
	p->security = NULL;
1054
#endif
1055
	p->cap_bset = current->cap_bset;
L
Linus Torvalds 已提交
1056 1057
	p->io_context = NULL;
	p->audit_context = NULL;
1058
	cgroup_fork(p);
L
Linus Torvalds 已提交
1059
#ifdef CONFIG_NUMA
1060
	p->mempolicy = mpol_dup(p->mempolicy);
L
Linus Torvalds 已提交
1061 1062 1063
 	if (IS_ERR(p->mempolicy)) {
 		retval = PTR_ERR(p->mempolicy);
 		p->mempolicy = NULL;
1064
 		goto bad_fork_cleanup_cgroup;
L
Linus Torvalds 已提交
1065
 	}
1066
	mpol_fix_fork_child_flag(p);
L
Linus Torvalds 已提交
1067
#endif
1068 1069
#ifdef CONFIG_TRACE_IRQFLAGS
	p->irq_events = 0;
1070 1071 1072
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
	p->hardirqs_enabled = 1;
#else
1073
	p->hardirqs_enabled = 0;
1074
#endif
1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086
	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
I
Ingo Molnar 已提交
1087 1088 1089 1090 1091
#ifdef CONFIG_LOCKDEP
	p->lockdep_depth = 0; /* no locks held yet */
	p->curr_chain_key = 0;
	p->lockdep_recursion = 0;
#endif
L
Linus Torvalds 已提交
1092

1093 1094 1095 1096
#ifdef CONFIG_DEBUG_MUTEXES
	p->blocked_on = NULL; /* not blocked yet */
#endif

1097 1098 1099
	/* Perform scheduler related setup. Assign this task to a CPU. */
	sched_fork(p, clone_flags);

L
Linus Torvalds 已提交
1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118
	if ((retval = security_task_alloc(p)))
		goto bad_fork_cleanup_policy;
	if ((retval = audit_alloc(p)))
		goto bad_fork_cleanup_security;
	/* copy all the process information */
	if ((retval = copy_semundo(clone_flags, p)))
		goto bad_fork_cleanup_audit;
	if ((retval = copy_files(clone_flags, p)))
		goto bad_fork_cleanup_semundo;
	if ((retval = copy_fs(clone_flags, p)))
		goto bad_fork_cleanup_files;
	if ((retval = copy_sighand(clone_flags, p)))
		goto bad_fork_cleanup_fs;
	if ((retval = copy_signal(clone_flags, p)))
		goto bad_fork_cleanup_sighand;
	if ((retval = copy_mm(clone_flags, p)))
		goto bad_fork_cleanup_signal;
	if ((retval = copy_keys(clone_flags, p)))
		goto bad_fork_cleanup_mm;
S
Serge E. Hallyn 已提交
1119
	if ((retval = copy_namespaces(clone_flags, p)))
L
Linus Torvalds 已提交
1120
		goto bad_fork_cleanup_keys;
1121
	if ((retval = copy_io(clone_flags, p)))
1122
		goto bad_fork_cleanup_namespaces;
L
Linus Torvalds 已提交
1123 1124
	retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
	if (retval)
1125
		goto bad_fork_cleanup_io;
L
Linus Torvalds 已提交
1126

1127 1128 1129 1130
	if (pid != &init_struct_pid) {
		retval = -ENOMEM;
		pid = alloc_pid(task_active_pid_ns(p));
		if (!pid)
1131
			goto bad_fork_cleanup_io;
1132 1133 1134 1135 1136 1137

		if (clone_flags & CLONE_NEWPID) {
			retval = pid_ns_prepare_proc(task_active_pid_ns(p));
			if (retval < 0)
				goto bad_fork_free_pid;
		}
1138 1139 1140 1141 1142 1143 1144
	}

	p->pid = pid_nr(pid);
	p->tgid = p->pid;
	if (clone_flags & CLONE_THREAD)
		p->tgid = current->tgid;

1145 1146 1147 1148 1149 1150
	if (current->nsproxy != p->nsproxy) {
		retval = ns_cgroup_clone(p, pid);
		if (retval)
			goto bad_fork_free_pid;
	}

L
Linus Torvalds 已提交
1151 1152 1153 1154 1155
	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;
1156
#ifdef CONFIG_FUTEX
1157 1158 1159 1160
	p->robust_list = NULL;
#ifdef CONFIG_COMPAT
	p->compat_robust_list = NULL;
#endif
1161 1162
	INIT_LIST_HEAD(&p->pi_state_list);
	p->pi_state_cache = NULL;
1163
#endif
1164 1165 1166 1167 1168 1169
	/*
	 * sigaltstack should be cleared when sharing the same VM
	 */
	if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
		p->sas_ss_sp = p->sas_ss_size = 0;

L
Linus Torvalds 已提交
1170 1171 1172 1173 1174
	/*
	 * Syscall tracing should be turned off in the child regardless
	 * of CLONE_PTRACE.
	 */
	clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1175 1176 1177
#ifdef TIF_SYSCALL_EMU
	clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
#endif
A
Arjan van de Ven 已提交
1178
	clear_all_latency_tracing(p);
L
Linus Torvalds 已提交
1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193

	/* Our parent execution domain becomes current domain
	   These must match for thread signalling to apply */
	p->parent_exec_id = p->self_exec_id;

	/* ok, now we should be set up.. */
	p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
	p->pdeath_signal = 0;
	p->exit_state = 0;

	/*
	 * Ok, make it visible to the rest of the system.
	 * We dont wake it up yet.
	 */
	p->group_leader = p;
O
Oleg Nesterov 已提交
1194
	INIT_LIST_HEAD(&p->thread_group);
L
Linus Torvalds 已提交
1195

1196 1197 1198 1199 1200 1201
	/* Now that the task is set up, run cgroup callbacks if
	 * necessary. We need to run them before the task is visible
	 * on the tasklist. */
	cgroup_fork_callbacks(p);
	cgroup_callbacks_done = 1;

L
Linus Torvalds 已提交
1202 1203 1204 1205
	/* Need tasklist lock for parent etc handling! */
	write_lock_irq(&tasklist_lock);

	/*
N
Nick Piggin 已提交
1206 1207 1208 1209 1210 1211 1212
	 * The task hasn't been attached yet, so its cpus_allowed mask will
	 * not be changed, nor will its assigned CPU.
	 *
	 * The cpus_allowed mask of the parent may have changed after it was
	 * copied first time - so re-copy it here, then check the child's CPU
	 * to ensure it is on a valid CPU (and if not, just force it back to
	 * parent's CPU). This avoids alot of nasty races.
L
Linus Torvalds 已提交
1213 1214
	 */
	p->cpus_allowed = current->cpus_allowed;
P
Peter Zijlstra 已提交
1215
	p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1216 1217
	if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
			!cpu_online(task_cpu(p))))
N
Nick Piggin 已提交
1218
		set_task_cpu(p, smp_processor_id());
L
Linus Torvalds 已提交
1219 1220 1221 1222 1223 1224 1225

	/* CLONE_PARENT re-uses the old parent */
	if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
		p->real_parent = current->real_parent;
	else
		p->real_parent = current;

1226
	spin_lock(&current->sighand->siglock);
1227 1228 1229 1230 1231 1232 1233 1234 1235

	/*
	 * 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).
 	 */
D
Daniel Walker 已提交
1236
	recalc_sigpending();
1237 1238 1239 1240
	if (signal_pending(current)) {
		spin_unlock(&current->sighand->siglock);
		write_unlock_irq(&tasklist_lock);
		retval = -ERESTARTNOINTR;
1241
		goto bad_fork_free_pid;
1242 1243
	}

L
Linus Torvalds 已提交
1244 1245
	if (clone_flags & CLONE_THREAD) {
		p->group_leader = current->group_leader;
O
Oleg Nesterov 已提交
1246
		list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
L
Linus Torvalds 已提交
1247 1248
	}

1249
	if (likely(p->pid)) {
R
Roland McGrath 已提交
1250
		list_add_tail(&p->sibling, &p->real_parent->children);
R
Roland McGrath 已提交
1251
		tracehook_finish_clone(p, clone_flags, trace);
1252 1253

		if (thread_group_leader(p)) {
E
Eric W. Biederman 已提交
1254
			if (clone_flags & CLONE_NEWPID)
1255
				p->nsproxy->pid_ns->child_reaper = p;
1256

1257
			p->signal->leader_pid = pid;
A
Alan Cox 已提交
1258 1259
			tty_kref_put(p->signal->tty);
			p->signal->tty = tty_kref_get(current->signal->tty);
E
Eric W. Biederman 已提交
1260 1261 1262 1263
			set_task_pgrp(p, task_pgrp_nr(current));
			set_task_session(p, task_session_nr(current));
			attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
			attach_pid(p, PIDTYPE_SID, task_session(current));
1264
			list_add_tail_rcu(&p->tasks, &init_task.tasks);
L
Linus Torvalds 已提交
1265
			__get_cpu_var(process_counts)++;
1266
		}
1267
		attach_pid(p, PIDTYPE_PID, pid);
1268
		nr_threads++;
L
Linus Torvalds 已提交
1269 1270 1271
	}

	total_forks++;
1272
	spin_unlock(&current->sighand->siglock);
L
Linus Torvalds 已提交
1273
	write_unlock_irq(&tasklist_lock);
1274
	ftrace_retfunc_init_task(p);
1275
	proc_fork_connector(p);
1276
	cgroup_post_fork(p);
L
Linus Torvalds 已提交
1277 1278
	return p;

1279 1280 1281
bad_fork_free_pid:
	if (pid != &init_struct_pid)
		free_pid(pid);
1282 1283
bad_fork_cleanup_io:
	put_io_context(p->io_context);
S
Serge E. Hallyn 已提交
1284
bad_fork_cleanup_namespaces:
1285
	exit_task_namespaces(p);
L
Linus Torvalds 已提交
1286 1287 1288 1289 1290 1291
bad_fork_cleanup_keys:
	exit_keys(p);
bad_fork_cleanup_mm:
	if (p->mm)
		mmput(p->mm);
bad_fork_cleanup_signal:
1292
	cleanup_signal(p);
L
Linus Torvalds 已提交
1293
bad_fork_cleanup_sighand:
1294
	__cleanup_sighand(p->sighand);
L
Linus Torvalds 已提交
1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306
bad_fork_cleanup_fs:
	exit_fs(p); /* blocking */
bad_fork_cleanup_files:
	exit_files(p); /* blocking */
bad_fork_cleanup_semundo:
	exit_sem(p);
bad_fork_cleanup_audit:
	audit_free(p);
bad_fork_cleanup_security:
	security_task_free(p);
bad_fork_cleanup_policy:
#ifdef CONFIG_NUMA
1307
	mpol_put(p->mempolicy);
1308
bad_fork_cleanup_cgroup:
L
Linus Torvalds 已提交
1309
#endif
1310
	cgroup_exit(p, cgroup_callbacks_done);
1311
	delayacct_tsk_free(p);
L
Linus Torvalds 已提交
1312 1313 1314
	if (p->binfmt)
		module_put(p->binfmt->module);
bad_fork_cleanup_put_domain:
A
Al Viro 已提交
1315
	module_put(task_thread_info(p)->exec_domain->module);
L
Linus Torvalds 已提交
1316 1317 1318 1319 1320 1321
bad_fork_cleanup_count:
	put_group_info(p->group_info);
	atomic_dec(&p->user->processes);
	free_uid(p->user);
bad_fork_free:
	free_task(p);
1322 1323
fork_out:
	return ERR_PTR(retval);
L
Linus Torvalds 已提交
1324 1325
}

A
Adrian Bunk 已提交
1326
noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
L
Linus Torvalds 已提交
1327 1328 1329 1330 1331
{
	memset(regs, 0, sizeof(struct pt_regs));
	return regs;
}

1332
struct task_struct * __cpuinit fork_idle(int cpu)
L
Linus Torvalds 已提交
1333
{
1334
	struct task_struct *task;
L
Linus Torvalds 已提交
1335 1336
	struct pt_regs regs;

1337
	task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
R
Roland McGrath 已提交
1338
			    &init_struct_pid, 0);
1339 1340
	if (!IS_ERR(task))
		init_idle(task, cpu);
1341

L
Linus Torvalds 已提交
1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359
	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.
 */
long do_fork(unsigned long clone_flags,
	      unsigned long stack_start,
	      struct pt_regs *regs,
	      unsigned long stack_size,
	      int __user *parent_tidptr,
	      int __user *child_tidptr)
{
	struct task_struct *p;
	int trace = 0;
1360
	long nr;
L
Linus Torvalds 已提交
1361

1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378
	/*
	 * We hope to recycle these flags after 2.6.26
	 */
	if (unlikely(clone_flags & CLONE_STOPPED)) {
		static int __read_mostly count = 100;

		if (count > 0 && printk_ratelimit()) {
			char comm[TASK_COMM_LEN];

			count--;
			printk(KERN_INFO "fork(): process `%s' used deprecated "
					"clone flags 0x%lx\n",
				get_task_comm(comm, current),
				clone_flags & CLONE_STOPPED);
		}
	}

R
Roland McGrath 已提交
1379 1380 1381 1382 1383
	/*
	 * When called from kernel_thread, don't do user tracing stuff.
	 */
	if (likely(user_mode(regs)))
		trace = tracehook_prepare_clone(clone_flags);
L
Linus Torvalds 已提交
1384

1385
	p = copy_process(clone_flags, stack_start, regs, stack_size,
R
Roland McGrath 已提交
1386
			 child_tidptr, NULL, trace);
L
Linus Torvalds 已提交
1387 1388 1389 1390 1391 1392 1393
	/*
	 * Do this prior waking up the new thread - the thread pointer
	 * might get invalid after that point, if the thread exits quickly.
	 */
	if (!IS_ERR(p)) {
		struct completion vfork;

1394 1395
		trace_sched_process_fork(current, p);

1396
		nr = task_pid_vnr(p);
1397 1398 1399

		if (clone_flags & CLONE_PARENT_SETTID)
			put_user(nr, parent_tidptr);
1400

L
Linus Torvalds 已提交
1401 1402 1403 1404 1405
		if (clone_flags & CLONE_VFORK) {
			p->vfork_done = &vfork;
			init_completion(&vfork);
		}

R
Roland McGrath 已提交
1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416
		tracehook_report_clone(trace, regs, clone_flags, nr, p);

		/*
		 * We set PF_STARTING at creation in case tracing wants to
		 * use this to distinguish a fully live task from one that
		 * hasn't gotten to tracehook_report_clone() yet.  Now we
		 * clear it and set the child going.
		 */
		p->flags &= ~PF_STARTING;

		if (unlikely(clone_flags & CLONE_STOPPED)) {
L
Linus Torvalds 已提交
1417 1418 1419 1420 1421
			/*
			 * We'll start up with an immediate SIGSTOP.
			 */
			sigaddset(&p->pending.signal, SIGSTOP);
			set_tsk_thread_flag(p, TIF_SIGPENDING);
1422
			__set_task_state(p, TASK_STOPPED);
R
Roland McGrath 已提交
1423 1424
		} else {
			wake_up_new_task(p, clone_flags);
L
Linus Torvalds 已提交
1425 1426
		}

R
Roland McGrath 已提交
1427 1428 1429
		tracehook_report_clone_complete(trace, regs,
						clone_flags, nr, p);

L
Linus Torvalds 已提交
1430
		if (clone_flags & CLONE_VFORK) {
R
Rafael J. Wysocki 已提交
1431
			freezer_do_not_count();
L
Linus Torvalds 已提交
1432
			wait_for_completion(&vfork);
R
Rafael J. Wysocki 已提交
1433
			freezer_count();
R
Roland McGrath 已提交
1434
			tracehook_report_vfork_done(p, nr);
L
Linus Torvalds 已提交
1435 1436
		}
	} else {
1437
		nr = PTR_ERR(p);
L
Linus Torvalds 已提交
1438
	}
1439
	return nr;
L
Linus Torvalds 已提交
1440 1441
}

1442 1443 1444 1445
#ifndef ARCH_MIN_MMSTRUCT_ALIGN
#define ARCH_MIN_MMSTRUCT_ALIGN 0
#endif

1446
static void sighand_ctor(void *data)
1447 1448 1449
{
	struct sighand_struct *sighand = data;

C
Christoph Lameter 已提交
1450
	spin_lock_init(&sighand->siglock);
D
Davide Libenzi 已提交
1451
	init_waitqueue_head(&sighand->signalfd_wqh);
1452 1453
}

L
Linus Torvalds 已提交
1454 1455 1456 1457
void __init proc_caches_init(void)
{
	sighand_cachep = kmem_cache_create("sighand_cache",
			sizeof(struct sighand_struct), 0,
1458
			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1459
			sighand_ctor);
L
Linus Torvalds 已提交
1460 1461
	signal_cachep = kmem_cache_create("signal_cache",
			sizeof(struct signal_struct), 0,
1462 1463
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
	files_cachep = kmem_cache_create("files_cache",
L
Linus Torvalds 已提交
1464
			sizeof(struct files_struct), 0,
1465 1466
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
	fs_cachep = kmem_cache_create("fs_cache",
L
Linus Torvalds 已提交
1467
			sizeof(struct fs_struct), 0,
1468
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
L
Linus Torvalds 已提交
1469 1470
	vm_area_cachep = kmem_cache_create("vm_area_struct",
			sizeof(struct vm_area_struct), 0,
1471
			SLAB_PANIC, NULL);
L
Linus Torvalds 已提交
1472
	mm_cachep = kmem_cache_create("mm_struct",
1473
			sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1474
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
L
Linus Torvalds 已提交
1475
}
1476 1477 1478 1479 1480

/*
 * Check constraints on flags passed to the unshare system call and
 * force unsharing of additional process context as appropriate.
 */
A
Alexey Dobriyan 已提交
1481
static void check_unshare_flags(unsigned long *flags_ptr)
1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522
{
	/*
	 * If unsharing a thread from a thread group, must also
	 * unshare vm.
	 */
	if (*flags_ptr & CLONE_THREAD)
		*flags_ptr |= CLONE_VM;

	/*
	 * If unsharing vm, must also unshare signal handlers.
	 */
	if (*flags_ptr & CLONE_VM)
		*flags_ptr |= CLONE_SIGHAND;

	/*
	 * If unsharing signal handlers and the task was created
	 * using CLONE_THREAD, then must unshare the thread
	 */
	if ((*flags_ptr & CLONE_SIGHAND) &&
	    (atomic_read(&current->signal->count) > 1))
		*flags_ptr |= CLONE_THREAD;

	/*
	 * If unsharing namespace, must also unshare filesystem information.
	 */
	if (*flags_ptr & CLONE_NEWNS)
		*flags_ptr |= CLONE_FS;
}

/*
 * Unsharing of tasks created with CLONE_THREAD is not supported yet
 */
static int unshare_thread(unsigned long unshare_flags)
{
	if (unshare_flags & CLONE_THREAD)
		return -EINVAL;

	return 0;
}

/*
1523
 * Unshare the filesystem structure if it is being shared
1524 1525 1526 1527 1528 1529
 */
static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
{
	struct fs_struct *fs = current->fs;

	if ((unshare_flags & CLONE_FS) &&
1530 1531 1532 1533 1534
	    (fs && atomic_read(&fs->count) > 1)) {
		*new_fsp = __copy_fs_struct(current->fs);
		if (!*new_fsp)
			return -ENOMEM;
	}
1535 1536 1537 1538 1539

	return 0;
}

/*
1540
 * Unsharing of sighand is not supported yet
1541 1542 1543 1544 1545
 */
static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
{
	struct sighand_struct *sigh = current->sighand;

1546
	if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1547 1548 1549 1550 1551 1552
		return -EINVAL;
	else
		return 0;
}

/*
1553
 * Unshare vm if it is being shared
1554 1555 1556 1557 1558 1559
 */
static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
{
	struct mm_struct *mm = current->mm;

	if ((unshare_flags & CLONE_VM) &&
1560
	    (mm && atomic_read(&mm->mm_users) > 1)) {
1561
		return -EINVAL;
1562
	}
1563 1564 1565 1566 1567

	return 0;
}

/*
1568
 * Unshare file descriptor table if it is being shared
1569 1570 1571 1572
 */
static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
{
	struct files_struct *fd = current->files;
1573
	int error = 0;
1574 1575

	if ((unshare_flags & CLONE_FILES) &&
1576 1577 1578 1579 1580
	    (fd && atomic_read(&fd->count) > 1)) {
		*new_fdp = dup_fd(fd, &error);
		if (!*new_fdp)
			return error;
	}
1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596

	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.
 */
asmlinkage long sys_unshare(unsigned long unshare_flags)
{
	int err = 0;
	struct fs_struct *fs, *new_fs = NULL;
1597
	struct sighand_struct *new_sigh = NULL;
1598 1599
	struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
	struct files_struct *fd, *new_fd = NULL;
1600
	struct nsproxy *new_nsproxy = NULL;
1601
	int do_sysvsem = 0;
1602 1603 1604

	check_unshare_flags(&unshare_flags);

1605 1606 1607
	/* Return -EINVAL for all unsupported flags */
	err = -EINVAL;
	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
K
Kirill Korotaev 已提交
1608
				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1609 1610
				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|
				CLONE_NEWNET))
1611 1612
		goto bad_unshare_out;

1613 1614 1615 1616 1617 1618
	/*
	 * 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))
1619
		do_sysvsem = 1;
1620 1621 1622 1623 1624
	if ((err = unshare_thread(unshare_flags)))
		goto bad_unshare_out;
	if ((err = unshare_fs(unshare_flags, &new_fs)))
		goto bad_unshare_cleanup_thread;
	if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1625
		goto bad_unshare_cleanup_fs;
1626 1627 1628 1629
	if ((err = unshare_vm(unshare_flags, &new_mm)))
		goto bad_unshare_cleanup_sigh;
	if ((err = unshare_fd(unshare_flags, &new_fd)))
		goto bad_unshare_cleanup_vm;
1630 1631
	if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
			new_fs)))
1632
		goto bad_unshare_cleanup_fd;
1633

1634 1635 1636 1637 1638 1639 1640
	if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
		if (do_sysvsem) {
			/*
			 * CLONE_SYSVSEM is equivalent to sys_exit().
			 */
			exit_sem(current);
		}
S
Serge E. Hallyn 已提交
1641

1642
		if (new_nsproxy) {
1643 1644
			switch_task_namespaces(current, new_nsproxy);
			new_nsproxy = NULL;
1645
		}
1646

1647 1648
		task_lock(current);

1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672
		if (new_fs) {
			fs = current->fs;
			current->fs = new_fs;
			new_fs = fs;
		}

		if (new_mm) {
			mm = current->mm;
			active_mm = current->active_mm;
			current->mm = new_mm;
			current->active_mm = new_mm;
			activate_mm(active_mm, new_mm);
			new_mm = mm;
		}

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

		task_unlock(current);
	}

1673
	if (new_nsproxy)
1674
		put_nsproxy(new_nsproxy);
1675

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bad_unshare_cleanup_fd:
	if (new_fd)
		put_files_struct(new_fd);

bad_unshare_cleanup_vm:
	if (new_mm)
		mmput(new_mm);

bad_unshare_cleanup_sigh:
	if (new_sigh)
		if (atomic_dec_and_test(&new_sigh->count))
			kmem_cache_free(sighand_cachep, new_sigh);

bad_unshare_cleanup_fs:
	if (new_fs)
		put_fs_struct(new_fs);

bad_unshare_cleanup_thread:
bad_unshare_out:
	return err;
}
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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;
1707
	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;
}