fork.c 41.4 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_graph_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);

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	put_cred(tsk->real_cred);
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	put_cred(tsk->cred);
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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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			struct address_space *mapping = file->f_mapping;

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			get_file(file);
			if (tmp->vm_flags & VM_DENYWRITE)
				atomic_dec(&inode->i_writecount);
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			spin_lock(&mapping->i_mmap_lock);
			if (tmp->vm_flags & VM_SHARED)
				mapping->i_mmap_writable++;
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			tmp->vm_truncate_count = mpnt->vm_truncate_count;
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			flush_dcache_mmap_lock(mapping);
			/* insert tmp into the share list, just after mpnt */
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			vma_prio_tree_add(tmp, mpnt);
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			flush_dcache_mmap_unlock(mapping);
			spin_unlock(&mapping->i_mmap_lock);
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		}

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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)))

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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 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 : default_dump_filter;
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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);
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	spin_lock_init(&mm->ioctx_lock);
	INIT_HLIST_HEAD(&mm->ioctx_list);
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	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);
	}
558 559 560 561 562 563 564 565 566 567

	/*
	 * 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) {
L
Linus Torvalds 已提交
568 569 570 571 572 573 574 575 576 577 578 579
		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);
	}
}

580 581 582 583
/*
 * Allocate a new mm structure and copy contents from the
 * mm structure of the passed in task structure.
 */
584
struct mm_struct *dup_mm(struct task_struct *tsk)
585 586 587 588 589 590 591 592 593 594 595 596 597
{
	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));

598 599 600 601
	/* Initializing for Swap token stuff */
	mm->token_priority = 0;
	mm->last_interval = 0;

602
	if (!mm_init(mm, tsk))
603 604 605 606 607
		goto fail_nomem;

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

M
Matt Helsley 已提交
608 609
	dup_mm_exe_file(oldmm, mm);

610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634
	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
635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661
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;
662
	mm = dup_mm(tsk);
L
Linus Torvalds 已提交
663 664 665 666
	if (!mm)
		goto fail_nomem;

good_mm:
667 668 669 670
	/* Initializing for Swap token stuff */
	mm->token_priority = 0;
	mm->last_interval = 0;

L
Linus Torvalds 已提交
671 672 673 674 675 676 677 678
	tsk->mm = mm;
	tsk->active_mm = mm;
	return 0;

fail_nomem:
	return retval;
}

A
Alexey Dobriyan 已提交
679
static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
L
Linus Torvalds 已提交
680 681 682 683 684 685 686 687
{
	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
688 689 690 691
		fs->root = old->root;
		path_get(&old->root);
		fs->pwd = old->pwd;
		path_get(&old->pwd);
L
Linus Torvalds 已提交
692 693 694 695 696 697 698 699 700 701 702 703
		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
704
static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
L
Linus Torvalds 已提交
705 706 707 708 709 710 711 712 713 714 715
{
	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;
}

716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742
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;
}

743
static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
744 745 746 747 748 749
{
#ifdef CONFIG_BLOCK
	struct io_context *ioc = current->io_context;

	if (!ioc)
		return 0;
750 751 752 753 754 755 756 757
	/*
	 * 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)) {
758 759 760 761 762 763 764 765 766 767
		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
768
static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
L
Linus Torvalds 已提交
769 770 771
{
	struct sighand_struct *sig;

Z
Zhaolei 已提交
772
	if (clone_flags & CLONE_SIGHAND) {
L
Linus Torvalds 已提交
773 774 775 776
		atomic_inc(&current->sighand->count);
		return 0;
	}
	sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
I
Ingo Molnar 已提交
777
	rcu_assign_pointer(tsk->sighand, sig);
L
Linus Torvalds 已提交
778 779 780 781 782 783 784
	if (!sig)
		return -ENOMEM;
	atomic_set(&sig->count, 1);
	memcpy(sig->action, current->sighand->action, sizeof(sig->action));
	return 0;
}

785
void __cleanup_sighand(struct sighand_struct *sighand)
786 787 788 789 790
{
	if (atomic_dec_and_test(&sighand->count))
		kmem_cache_free(sighand_cachep, sighand);
}

791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816

/*
 * 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
817
static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
L
Linus Torvalds 已提交
818 819 820 821 822
{
	struct signal_struct *sig;
	int ret;

	if (clone_flags & CLONE_THREAD) {
823
		ret = thread_group_cputime_clone_thread(current);
824 825 826 827 828
		if (likely(!ret)) {
			atomic_inc(&current->signal->count);
			atomic_inc(&current->signal->live);
		}
		return ret;
L
Linus Torvalds 已提交
829 830 831 832 833 834 835 836 837 838 839 840 841
	}
	sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
	tsk->signal = sig;
	if (!sig)
		return -ENOMEM;

	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;
842
	sig->curr_target = tsk;
L
Linus Torvalds 已提交
843 844 845
	init_sigpending(&sig->shared_pending);
	INIT_LIST_HEAD(&sig->posix_timers);

846
	hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
847
	sig->it_real_incr.tv64 = 0;
L
Linus Torvalds 已提交
848 849 850
	sig->real_timer.function = it_real_fn;

	sig->leader = 0;	/* session leadership doesn't inherit */
851
	sig->tty_old_pgrp = NULL;
A
Alan Cox 已提交
852
	sig->tty = NULL;
L
Linus Torvalds 已提交
853

854
	sig->cutime = sig->cstime = cputime_zero;
855 856
	sig->gtime = cputime_zero;
	sig->cgtime = cputime_zero;
L
Linus Torvalds 已提交
857 858
	sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
	sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
859
	sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
860
	task_io_accounting_init(&sig->ioac);
861
	taskstats_tgid_init(sig);
L
Linus Torvalds 已提交
862 863 864 865 866

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

867 868
	posix_cpu_timers_init_group(sig);

869
	acct_init_pacct(&sig->pacct);
L
Linus Torvalds 已提交
870

M
Miloslav Trmac 已提交
871 872
	tty_audit_fork(sig);

L
Linus Torvalds 已提交
873 874 875
	return 0;
}

876 877
void __cleanup_signal(struct signal_struct *sig)
{
878
	thread_group_cputime_free(sig);
A
Alan Cox 已提交
879
	tty_kref_put(sig->tty);
880 881 882
	kmem_cache_free(signal_cachep, sig);
}

A
Alexey Dobriyan 已提交
883
static void cleanup_signal(struct task_struct *tsk)
884 885 886 887 888 889 890 891 892
{
	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
893
static void copy_flags(unsigned long clone_flags, struct task_struct *p)
L
Linus Torvalds 已提交
894 895 896
{
	unsigned long new_flags = p->flags;

897
	new_flags &= ~PF_SUPERPRIV;
L
Linus Torvalds 已提交
898
	new_flags |= PF_FORKNOEXEC;
R
Roland McGrath 已提交
899
	new_flags |= PF_STARTING;
L
Linus Torvalds 已提交
900
	p->flags = new_flags;
901
	clear_freeze_flag(p);
L
Linus Torvalds 已提交
902 903 904 905 906 907
}

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

908
	return task_pid_vnr(current);
L
Linus Torvalds 已提交
909 910
}

A
Alexey Dobriyan 已提交
911
static void rt_mutex_init_task(struct task_struct *p)
I
Ingo Molnar 已提交
912 913
{
	spin_lock_init(&p->pi_lock);
914
#ifdef CONFIG_RT_MUTEXES
I
Ingo Molnar 已提交
915 916 917 918 919
	plist_head_init(&p->pi_waiters, &p->pi_lock);
	p->pi_blocked_on = NULL;
#endif
}

920 921 922 923 924 925 926
#ifdef CONFIG_MM_OWNER
void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
{
	mm->owner = p;
}
#endif /* CONFIG_MM_OWNER */

927 928 929 930 931 932 933 934 935 936 937 938 939
/*
 * 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
940 941 942 943 944 945 946 947
/*
 * 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.
 */
948 949 950 951 952
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
953 954
					struct pid *pid,
					int trace)
L
Linus Torvalds 已提交
955 956
{
	int retval;
957
	struct task_struct *p;
958
	int cgroup_callbacks_done = 0;
L
Linus Torvalds 已提交
959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986

	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;

987 988
	rt_mutex_init_task(p);

I
Ingo Molnar 已提交
989
#ifdef CONFIG_PROVE_LOCKING
990 991 992
	DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
	DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
#endif
L
Linus Torvalds 已提交
993
	retval = -EAGAIN;
994
	if (atomic_read(&p->real_cred->user->processes) >=
L
Linus Torvalds 已提交
995 996
			p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
		if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
997
		    p->real_cred->user != INIT_USER)
L
Linus Torvalds 已提交
998 999 1000
			goto bad_fork_free;
	}

1001 1002 1003
	retval = copy_creds(p, clone_flags);
	if (retval < 0)
		goto bad_fork_free;
L
Linus Torvalds 已提交
1004 1005 1006 1007 1008 1009 1010 1011 1012

	/*
	 * 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
1013
	if (!try_module_get(task_thread_info(p)->exec_domain->module))
L
Linus Torvalds 已提交
1014 1015 1016 1017 1018 1019
		goto bad_fork_cleanup_count;

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

	p->did_exec = 0;
1020
	delayacct_tsk_init(p);	/* Must remain after dup_task_struct() */
L
Linus Torvalds 已提交
1021 1022 1023
	copy_flags(clone_flags, p);
	INIT_LIST_HEAD(&p->children);
	INIT_LIST_HEAD(&p->sibling);
P
Paul E. McKenney 已提交
1024 1025 1026 1027
#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
1028 1029 1030 1031 1032 1033 1034 1035
	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;
1036
	p->gtime = cputime_zero;
1037 1038
	p->utimescaled = cputime_zero;
	p->stimescaled = cputime_zero;
P
Peter Zijlstra 已提交
1039
	p->prev_utime = cputime_zero;
1040
	p->prev_stime = cputime_zero;
1041

1042 1043
	p->default_timer_slack_ns = current->timer_slack_ns;

1044 1045 1046 1047 1048
#ifdef CONFIG_DETECT_SOFTLOCKUP
	p->last_switch_count = 0;
	p->last_switch_timestamp = 0;
#endif

1049
	task_io_accounting_init(&p->ioac);
L
Linus Torvalds 已提交
1050 1051
	acct_clear_integrals(p);

1052
	posix_cpu_timers_init(p);
L
Linus Torvalds 已提交
1053 1054 1055

	p->lock_depth = -1;		/* -1 = no lock */
	do_posix_clock_monotonic_gettime(&p->start_time);
1056 1057
	p->real_start_time = p->start_time;
	monotonic_to_bootbased(&p->real_start_time);
L
Linus Torvalds 已提交
1058 1059
	p->io_context = NULL;
	p->audit_context = NULL;
1060
	cgroup_fork(p);
L
Linus Torvalds 已提交
1061
#ifdef CONFIG_NUMA
1062
	p->mempolicy = mpol_dup(p->mempolicy);
L
Linus Torvalds 已提交
1063 1064 1065
 	if (IS_ERR(p->mempolicy)) {
 		retval = PTR_ERR(p->mempolicy);
 		p->mempolicy = NULL;
1066
 		goto bad_fork_cleanup_cgroup;
L
Linus Torvalds 已提交
1067
 	}
1068
	mpol_fix_fork_child_flag(p);
L
Linus Torvalds 已提交
1069
#endif
1070 1071
#ifdef CONFIG_TRACE_IRQFLAGS
	p->irq_events = 0;
1072 1073 1074
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
	p->hardirqs_enabled = 1;
#else
1075
	p->hardirqs_enabled = 0;
1076
#endif
1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088
	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
1089 1090 1091 1092 1093
#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
1094

1095 1096 1097
#ifdef CONFIG_DEBUG_MUTEXES
	p->blocked_on = NULL; /* not blocked yet */
#endif
1098 1099
	if (unlikely(ptrace_reparented(current)))
		ptrace_fork(p, clone_flags);
1100

1101 1102 1103
	/* Perform scheduler related setup. Assign this task to a CPU. */
	sched_fork(p, clone_flags);

L
Linus Torvalds 已提交
1104
	if ((retval = audit_alloc(p)))
1105
		goto bad_fork_cleanup_policy;
L
Linus Torvalds 已提交
1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118
	/* 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;
S
Serge E. Hallyn 已提交
1119
	if ((retval = copy_namespaces(clone_flags, p)))
D
David Howells 已提交
1120
		goto bad_fork_cleanup_mm;
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
	if (pid != &init_struct_pid) {
		retval = -ENOMEM;
1129
		pid = alloc_pid(p->nsproxy->pid_ns);
1130
		if (!pid)
1131
			goto bad_fork_cleanup_io;
1132 1133

		if (clone_flags & CLONE_NEWPID) {
1134
			retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1135 1136 1137
			if (retval < 0)
				goto bad_fork_free_pid;
		}
1138 1139
	}

1140 1141
	ftrace_graph_init_task(p);

1142 1143 1144 1145 1146
	p->pid = pid_nr(pid);
	p->tgid = p->pid;
	if (clone_flags & CLONE_THREAD)
		p->tgid = current->tgid;

1147 1148 1149
	if (current->nsproxy != p->nsproxy) {
		retval = ns_cgroup_clone(p, pid);
		if (retval)
1150
			goto bad_fork_free_graph;
1151 1152
	}

L
Linus Torvalds 已提交
1153 1154 1155 1156 1157
	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;
1158
#ifdef CONFIG_FUTEX
1159 1160 1161 1162
	p->robust_list = NULL;
#ifdef CONFIG_COMPAT
	p->compat_robust_list = NULL;
#endif
1163 1164
	INIT_LIST_HEAD(&p->pi_state_list);
	p->pi_state_cache = NULL;
1165
#endif
1166 1167 1168 1169 1170 1171
	/*
	 * 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
1172 1173 1174 1175 1176
	/*
	 * Syscall tracing should be turned off in the child regardless
	 * of CLONE_PTRACE.
	 */
	clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1177 1178 1179
#ifdef TIF_SYSCALL_EMU
	clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
#endif
A
Arjan van de Ven 已提交
1180
	clear_all_latency_tracing(p);
L
Linus Torvalds 已提交
1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195

	/* 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
1196
	INIT_LIST_HEAD(&p->thread_group);
L
Linus Torvalds 已提交
1197

1198 1199 1200 1201 1202 1203
	/* 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
1204 1205 1206 1207
	/* Need tasklist lock for parent etc handling! */
	write_lock_irq(&tasklist_lock);

	/*
N
Nick Piggin 已提交
1208 1209 1210 1211 1212 1213 1214
	 * 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
1215 1216
	 */
	p->cpus_allowed = current->cpus_allowed;
P
Peter Zijlstra 已提交
1217
	p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1218 1219
	if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
			!cpu_online(task_cpu(p))))
N
Nick Piggin 已提交
1220
		set_task_cpu(p, smp_processor_id());
L
Linus Torvalds 已提交
1221 1222 1223 1224 1225 1226 1227

	/* 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;

1228
	spin_lock(&current->sighand->siglock);
1229 1230 1231 1232 1233 1234 1235 1236 1237

	/*
	 * 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
1238
	recalc_sigpending();
1239 1240 1241 1242
	if (signal_pending(current)) {
		spin_unlock(&current->sighand->siglock);
		write_unlock_irq(&tasklist_lock);
		retval = -ERESTARTNOINTR;
1243
		goto bad_fork_free_graph;
1244 1245
	}

L
Linus Torvalds 已提交
1246 1247
	if (clone_flags & CLONE_THREAD) {
		p->group_leader = current->group_leader;
O
Oleg Nesterov 已提交
1248
		list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
L
Linus Torvalds 已提交
1249 1250
	}

1251
	if (likely(p->pid)) {
R
Roland McGrath 已提交
1252
		list_add_tail(&p->sibling, &p->real_parent->children);
R
Roland McGrath 已提交
1253
		tracehook_finish_clone(p, clone_flags, trace);
1254 1255

		if (thread_group_leader(p)) {
E
Eric W. Biederman 已提交
1256
			if (clone_flags & CLONE_NEWPID)
1257
				p->nsproxy->pid_ns->child_reaper = p;
1258

1259
			p->signal->leader_pid = pid;
A
Alan Cox 已提交
1260 1261
			tty_kref_put(p->signal->tty);
			p->signal->tty = tty_kref_get(current->signal->tty);
E
Eric W. Biederman 已提交
1262 1263 1264 1265
			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));
1266
			list_add_tail_rcu(&p->tasks, &init_task.tasks);
L
Linus Torvalds 已提交
1267
			__get_cpu_var(process_counts)++;
1268
		}
1269
		attach_pid(p, PIDTYPE_PID, pid);
1270
		nr_threads++;
L
Linus Torvalds 已提交
1271 1272 1273
	}

	total_forks++;
1274
	spin_unlock(&current->sighand->siglock);
L
Linus Torvalds 已提交
1275
	write_unlock_irq(&tasklist_lock);
1276
	proc_fork_connector(p);
1277
	cgroup_post_fork(p);
L
Linus Torvalds 已提交
1278 1279
	return p;

1280 1281
bad_fork_free_graph:
	ftrace_graph_exit_task(p);
1282 1283 1284
bad_fork_free_pid:
	if (pid != &init_struct_pid)
		free_pid(pid);
1285 1286
bad_fork_cleanup_io:
	put_io_context(p->io_context);
S
Serge E. Hallyn 已提交
1287
bad_fork_cleanup_namespaces:
1288
	exit_task_namespaces(p);
L
Linus Torvalds 已提交
1289 1290 1291 1292
bad_fork_cleanup_mm:
	if (p->mm)
		mmput(p->mm);
bad_fork_cleanup_signal:
1293
	cleanup_signal(p);
L
Linus Torvalds 已提交
1294
bad_fork_cleanup_sighand:
1295
	__cleanup_sighand(p->sighand);
L
Linus Torvalds 已提交
1296 1297 1298 1299 1300 1301 1302 1303 1304 1305
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_policy:
#ifdef CONFIG_NUMA
1306
	mpol_put(p->mempolicy);
1307
bad_fork_cleanup_cgroup:
L
Linus Torvalds 已提交
1308
#endif
1309
	cgroup_exit(p, cgroup_callbacks_done);
1310
	delayacct_tsk_free(p);
L
Linus Torvalds 已提交
1311 1312 1313
	if (p->binfmt)
		module_put(p->binfmt->module);
bad_fork_cleanup_put_domain:
A
Al Viro 已提交
1314
	module_put(task_thread_info(p)->exec_domain->module);
L
Linus Torvalds 已提交
1315
bad_fork_cleanup_count:
D
David Howells 已提交
1316
	atomic_dec(&p->cred->user->processes);
1317
	put_cred(p->real_cred);
1318
	put_cred(p->cred);
L
Linus Torvalds 已提交
1319 1320
bad_fork_free:
	free_task(p);
1321 1322
fork_out:
	return ERR_PTR(retval);
L
Linus Torvalds 已提交
1323 1324
}

A
Adrian Bunk 已提交
1325
noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
L
Linus Torvalds 已提交
1326 1327 1328 1329 1330
{
	memset(regs, 0, sizeof(struct pt_regs));
	return regs;
}

1331
struct task_struct * __cpuinit fork_idle(int cpu)
L
Linus Torvalds 已提交
1332
{
1333
	struct task_struct *task;
L
Linus Torvalds 已提交
1334 1335
	struct pt_regs regs;

1336
	task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
R
Roland McGrath 已提交
1337
			    &init_struct_pid, 0);
1338 1339
	if (!IS_ERR(task))
		init_idle(task, cpu);
1340

L
Linus Torvalds 已提交
1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358
	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;
1359
	long nr;
L
Linus Torvalds 已提交
1360

1361 1362 1363 1364 1365 1366 1367 1368 1369 1370
	/*
	 * Do some preliminary argument and permissions checking before we
	 * actually start allocating stuff
	 */
	if (clone_flags & CLONE_NEWUSER) {
		if (clone_flags & CLONE_THREAD)
			return -EINVAL;
		/* hopefully this check will go away when userns support is
		 * complete
		 */
1371 1372
		if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
				!capable(CAP_SETGID))
1373 1374 1375
			return -EPERM;
	}

1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392
	/*
	 * 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
1393 1394 1395 1396 1397
	/*
	 * 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
1398

1399
	p = copy_process(clone_flags, stack_start, regs, stack_size,
R
Roland McGrath 已提交
1400
			 child_tidptr, NULL, trace);
L
Linus Torvalds 已提交
1401 1402 1403 1404 1405 1406 1407
	/*
	 * 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;

1408 1409
		trace_sched_process_fork(current, p);

1410
		nr = task_pid_vnr(p);
1411 1412 1413

		if (clone_flags & CLONE_PARENT_SETTID)
			put_user(nr, parent_tidptr);
1414

L
Linus Torvalds 已提交
1415 1416 1417 1418 1419
		if (clone_flags & CLONE_VFORK) {
			p->vfork_done = &vfork;
			init_completion(&vfork);
		}

1420
		audit_finish_fork(p);
R
Roland McGrath 已提交
1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431
		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
1432 1433 1434 1435 1436
			/*
			 * We'll start up with an immediate SIGSTOP.
			 */
			sigaddset(&p->pending.signal, SIGSTOP);
			set_tsk_thread_flag(p, TIF_SIGPENDING);
1437
			__set_task_state(p, TASK_STOPPED);
R
Roland McGrath 已提交
1438 1439
		} else {
			wake_up_new_task(p, clone_flags);
L
Linus Torvalds 已提交
1440 1441
		}

R
Roland McGrath 已提交
1442 1443 1444
		tracehook_report_clone_complete(trace, regs,
						clone_flags, nr, p);

L
Linus Torvalds 已提交
1445
		if (clone_flags & CLONE_VFORK) {
R
Rafael J. Wysocki 已提交
1446
			freezer_do_not_count();
L
Linus Torvalds 已提交
1447
			wait_for_completion(&vfork);
R
Rafael J. Wysocki 已提交
1448
			freezer_count();
R
Roland McGrath 已提交
1449
			tracehook_report_vfork_done(p, nr);
L
Linus Torvalds 已提交
1450 1451
		}
	} else {
1452
		nr = PTR_ERR(p);
L
Linus Torvalds 已提交
1453
	}
1454
	return nr;
L
Linus Torvalds 已提交
1455 1456
}

1457 1458 1459 1460
#ifndef ARCH_MIN_MMSTRUCT_ALIGN
#define ARCH_MIN_MMSTRUCT_ALIGN 0
#endif

1461
static void sighand_ctor(void *data)
1462 1463 1464
{
	struct sighand_struct *sighand = data;

C
Christoph Lameter 已提交
1465
	spin_lock_init(&sighand->siglock);
D
Davide Libenzi 已提交
1466
	init_waitqueue_head(&sighand->signalfd_wqh);
1467 1468
}

L
Linus Torvalds 已提交
1469 1470 1471 1472
void __init proc_caches_init(void)
{
	sighand_cachep = kmem_cache_create("sighand_cache",
			sizeof(struct sighand_struct), 0,
1473
			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1474
			sighand_ctor);
L
Linus Torvalds 已提交
1475 1476
	signal_cachep = kmem_cache_create("signal_cache",
			sizeof(struct signal_struct), 0,
1477 1478
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
	files_cachep = kmem_cache_create("files_cache",
L
Linus Torvalds 已提交
1479
			sizeof(struct files_struct), 0,
1480 1481
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
	fs_cachep = kmem_cache_create("fs_cache",
L
Linus Torvalds 已提交
1482
			sizeof(struct fs_struct), 0,
1483
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
L
Linus Torvalds 已提交
1484
	mm_cachep = kmem_cache_create("mm_struct",
1485
			sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1486
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1487
	mmap_init();
L
Linus Torvalds 已提交
1488
}
1489 1490 1491 1492 1493

/*
 * 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
1494
static void check_unshare_flags(unsigned long *flags_ptr)
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 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535
{
	/*
	 * 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;
}

/*
1536
 * Unshare the filesystem structure if it is being shared
1537 1538 1539 1540 1541 1542
 */
static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
{
	struct fs_struct *fs = current->fs;

	if ((unshare_flags & CLONE_FS) &&
1543 1544 1545 1546 1547
	    (fs && atomic_read(&fs->count) > 1)) {
		*new_fsp = __copy_fs_struct(current->fs);
		if (!*new_fsp)
			return -ENOMEM;
	}
1548 1549 1550 1551 1552

	return 0;
}

/*
1553
 * Unsharing of sighand is not supported yet
1554 1555 1556 1557 1558
 */
static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
{
	struct sighand_struct *sigh = current->sighand;

1559
	if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1560 1561 1562 1563 1564 1565
		return -EINVAL;
	else
		return 0;
}

/*
1566
 * Unshare vm if it is being shared
1567 1568 1569 1570 1571 1572
 */
static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
{
	struct mm_struct *mm = current->mm;

	if ((unshare_flags & CLONE_VM) &&
1573
	    (mm && atomic_read(&mm->mm_users) > 1)) {
1574
		return -EINVAL;
1575
	}
1576 1577 1578 1579 1580

	return 0;
}

/*
1581
 * Unshare file descriptor table if it is being shared
1582 1583 1584 1585
 */
static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
{
	struct files_struct *fd = current->files;
1586
	int error = 0;
1587 1588

	if ((unshare_flags & CLONE_FILES) &&
1589 1590 1591 1592 1593
	    (fd && atomic_read(&fd->count) > 1)) {
		*new_fdp = dup_fd(fd, &error);
		if (!*new_fdp)
			return error;
	}
1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609

	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;
1610
	struct sighand_struct *new_sigh = NULL;
1611 1612
	struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
	struct files_struct *fd, *new_fd = NULL;
1613
	struct nsproxy *new_nsproxy = NULL;
1614
	int do_sysvsem = 0;
1615 1616 1617

	check_unshare_flags(&unshare_flags);

1618 1619 1620
	/* 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
1621
				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1622
				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1623 1624
		goto bad_unshare_out;

1625 1626 1627 1628 1629 1630
	/*
	 * 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))
1631
		do_sysvsem = 1;
1632 1633 1634 1635 1636
	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)))
1637
		goto bad_unshare_cleanup_fs;
1638 1639 1640 1641
	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;
1642 1643
	if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
			new_fs)))
1644
		goto bad_unshare_cleanup_fd;
1645

1646 1647 1648 1649 1650 1651 1652
	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
1653

1654
		if (new_nsproxy) {
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			switch_task_namespaces(current, new_nsproxy);
			new_nsproxy = NULL;
1657
		}
1658

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		task_lock(current);

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		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);
	}

1685
	if (new_nsproxy)
1686
		put_nsproxy(new_nsproxy);
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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;
1719
	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;
}