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b4b27b9eed
linux/kernel/fork.c
Linus Torvalds b4b27b9eed Revert "signal: Allow tasks to cache one sigqueue struct" 
This reverts commits 4bad58ebc8 (and
399f8dd9a8, which tried to fix it).

I do not believe these are correct, and I'm about to release 5.13, so am
reverting them out of an abundance of caution.

The locking is odd, and appears broken.

On the allocation side (in __sigqueue_alloc()), the locking is somewhat
straightforward: it depends on sighand->siglock.  Since one caller
doesn't hold that lock, it further then tests 'sigqueue_flags' to avoid
the case with no locks held.

On the freeing side (in sigqueue_cache_or_free()), there is no locking
at all, and the logic instead depends on 'current' being a single
thread, and not able to race with itself.

To make things more exciting, there's also the data race between freeing
a signal and allocating one, which is handled by using WRITE_ONCE() and
READ_ONCE(), and being mutually exclusive wrt the initial state (ie
freeing will only free if the old state was NULL, while allocating will
obviously only use the value if it was non-NULL, so only one or the
other will actually act on the value).

However, while the free->alloc paths do seem mutually exclusive thanks
to just the data value dependency, it's not clear what the memory
ordering constraints are on it.  Could writes from the previous
allocation possibly be delayed and seen by the new allocation later,
causing logical inconsistencies?

So it's all very exciting and unusual.

And in particular, it seems that the freeing side is incorrect in
depending on "current" being single-threaded.  Yes, 'current' is a
single thread, but in the presense of asynchronous events even a single
thread can have data races.

And such asynchronous events can and do happen, with interrupts causing
signals to be flushed and thus free'd (for example - sending a
SIGCONT/SIGSTOP can happen from interrupt context, and can flush
previously queued process control signals).

So regardless of all the other questions about the memory ordering and
locking for this new cached allocation, the sigqueue_cache_or_free()
assumptions seem to be fundamentally incorrect.

It may be that people will show me the errors of my ways, and tell me
why this is all safe after all.  We can reinstate it if so.  But my
current belief is that the WRITE_ONCE() that sets the cached entry needs
to be a smp_store_release(), and the READ_ONCE() that finds a cached
entry needs to be a smp_load_acquire() to handle memory ordering
correctly.

And the sequence in sigqueue_cache_or_free() would need to either use a
lock or at least be interrupt-safe some way (perhaps by using something
like the percpu 'cmpxchg': it doesn't need to be SMP-safe, but like the
percpu operations it needs to be interrupt-safe).

Fixes: 399f8dd9a8 ("signal: Prevent sigqueue caching after task got released")
Fixes: 4bad58ebc8 ("signal: Allow tasks to cache one sigqueue struct")
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-06-27 13:32:54 -07:00

3112 lines
76 KiB
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// SPDX-License-Identifier: GPL-2.0-only
/*
* 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/anon_inodes.h>
#include <linux/slab.h>
#include <linux/sched/autogroup.h>
#include <linux/sched/mm.h>
#include <linux/sched/coredump.h>
#include <linux/sched/user.h>
#include <linux/sched/numa_balancing.h>
#include <linux/sched/stat.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/sched/cputime.h>
#include <linux/seq_file.h>
#include <linux/rtmutex.h>
#include <linux/init.h>
#include <linux/unistd.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/completion.h>
#include <linux/personality.h>
#include <linux/mempolicy.h>
#include <linux/sem.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/iocontext.h>
#include <linux/key.h>
#include <linux/binfmts.h>
#include <linux/mman.h>
#include <linux/mmu_notifier.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/vmacache.h>
#include <linux/nsproxy.h>
#include <linux/capability.h>
#include <linux/cpu.h>
#include <linux/cgroup.h>
#include <linux/security.h>
#include <linux/hugetlb.h>
#include <linux/seccomp.h>
#include <linux/swap.h>
#include <linux/syscalls.h>
#include <linux/jiffies.h>
#include <linux/futex.h>
#include <linux/compat.h>
#include <linux/kthread.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/rcupdate.h>
#include <linux/ptrace.h>
#include <linux/mount.h>
#include <linux/audit.h>
#include <linux/memcontrol.h>
#include <linux/ftrace.h>
#include <linux/proc_fs.h>
#include <linux/profile.h>
#include <linux/rmap.h>
#include <linux/ksm.h>
#include <linux/acct.h>
#include <linux/userfaultfd_k.h>
#include <linux/tsacct_kern.h>
#include <linux/cn_proc.h>
#include <linux/freezer.h>
#include <linux/delayacct.h>
#include <linux/taskstats_kern.h>
#include <linux/random.h>
#include <linux/tty.h>
#include <linux/blkdev.h>
#include <linux/fs_struct.h>
#include <linux/magic.h>
#include <linux/perf_event.h>
#include <linux/posix-timers.h>
#include <linux/user-return-notifier.h>
#include <linux/oom.h>
#include <linux/khugepaged.h>
#include <linux/signalfd.h>
#include <linux/uprobes.h>
#include <linux/aio.h>
#include <linux/compiler.h>
#include <linux/sysctl.h>
#include <linux/kcov.h>
#include <linux/livepatch.h>
#include <linux/thread_info.h>
#include <linux/stackleak.h>
#include <linux/kasan.h>
#include <linux/scs.h>
#include <linux/io_uring.h>
#include <linux/bpf.h>
#include <asm/pgalloc.h>
#include <linux/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#include <trace/events/sched.h>
#define CREATE_TRACE_POINTS
#include <trace/events/task.h>
/*
* Minimum number of threads to boot the kernel
*/
#define MIN_THREADS 20
/*
* Maximum number of threads
*/
#define MAX_THREADS FUTEX_TID_MASK
/*
* 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.. */
static int max_threads; /* tunable limit on nr_threads */
#define NAMED_ARRAY_INDEX(x) [x] = __stringify(x)
static const char * const resident_page_types[] = {
NAMED_ARRAY_INDEX(MM_FILEPAGES),
NAMED_ARRAY_INDEX(MM_ANONPAGES),
NAMED_ARRAY_INDEX(MM_SWAPENTS),
NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
};
DEFINE_PER_CPU(unsigned long, process_counts) = 0;
__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
#ifdef CONFIG_PROVE_RCU
int lockdep_tasklist_lock_is_held(void)
{
return lockdep_is_held(&tasklist_lock);
}
EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
#endif /* #ifdef CONFIG_PROVE_RCU */
int nr_processes(void)
{
int cpu;
int total = 0;
for_each_possible_cpu(cpu)
total += per_cpu(process_counts, cpu);
return total;
}
void __weak arch_release_task_struct(struct task_struct *tsk)
{
}
#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
static struct kmem_cache *task_struct_cachep;
static inline struct task_struct *alloc_task_struct_node(int node)
{
return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
}
static inline void free_task_struct(struct task_struct *tsk)
{
kmem_cache_free(task_struct_cachep, tsk);
}
#endif
#ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
/*
* Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
* kmemcache based allocator.
*/
# if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
#ifdef CONFIG_VMAP_STACK
/*
* vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
* flush. Try to minimize the number of calls by caching stacks.
*/
#define NR_CACHED_STACKS 2
static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
static int free_vm_stack_cache(unsigned int cpu)
{
struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
int i;
for (i = 0; i < NR_CACHED_STACKS; i++) {
struct vm_struct *vm_stack = cached_vm_stacks[i];
if (!vm_stack)
continue;
vfree(vm_stack->addr);
cached_vm_stacks[i] = NULL;
}
return 0;
}
#endif
static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
{
#ifdef CONFIG_VMAP_STACK
void *stack;
int i;
for (i = 0; i < NR_CACHED_STACKS; i++) {
struct vm_struct *s;
s = this_cpu_xchg(cached_stacks[i], NULL);
if (!s)
continue;
/* Mark stack accessible for KASAN. */
kasan_unpoison_range(s->addr, THREAD_SIZE);
/* Clear stale pointers from reused stack. */
memset(s->addr, 0, THREAD_SIZE);
tsk->stack_vm_area = s;
tsk->stack = s->addr;
return s->addr;
}
/*
* Allocated stacks are cached and later reused by new threads,
* so memcg accounting is performed manually on assigning/releasing
* stacks to tasks. Drop __GFP_ACCOUNT.
*/
stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
VMALLOC_START, VMALLOC_END,
THREADINFO_GFP & ~__GFP_ACCOUNT,
PAGE_KERNEL,
0, node, __builtin_return_address(0));
/*
* We can't call find_vm_area() in interrupt context, and
* free_thread_stack() can be called in interrupt context,
* so cache the vm_struct.
*/
if (stack) {
tsk->stack_vm_area = find_vm_area(stack);
tsk->stack = stack;
}
return stack;
#else
struct page *page = alloc_pages_node(node, THREADINFO_GFP,
THREAD_SIZE_ORDER);
if (likely(page)) {
tsk->stack = kasan_reset_tag(page_address(page));
return tsk->stack;
}
return NULL;
#endif
}
static inline void free_thread_stack(struct task_struct *tsk)
{
#ifdef CONFIG_VMAP_STACK
struct vm_struct *vm = task_stack_vm_area(tsk);
if (vm) {
int i;
for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
memcg_kmem_uncharge_page(vm->pages[i], 0);
for (i = 0; i < NR_CACHED_STACKS; i++) {
if (this_cpu_cmpxchg(cached_stacks[i],
NULL, tsk->stack_vm_area) != NULL)
continue;
return;
}
vfree_atomic(tsk->stack);
return;
}
#endif
__free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
}
# else
static struct kmem_cache *thread_stack_cache;
static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
int node)
{
unsigned long *stack;
stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
stack = kasan_reset_tag(stack);
tsk->stack = stack;
return stack;
}
static void free_thread_stack(struct task_struct *tsk)
{
kmem_cache_free(thread_stack_cache, tsk->stack);
}
void thread_stack_cache_init(void)
{
thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
THREAD_SIZE, THREAD_SIZE, 0, 0,
THREAD_SIZE, NULL);
BUG_ON(thread_stack_cache == NULL);
}
# endif
#endif
/* SLAB cache for signal_struct structures (tsk->signal) */
static struct kmem_cache *signal_cachep;
/* SLAB cache for sighand_struct structures (tsk->sighand) */
struct kmem_cache *sighand_cachep;
/* SLAB cache for files_struct structures (tsk->files) */
struct kmem_cache *files_cachep;
/* SLAB cache for fs_struct structures (tsk->fs) */
struct kmem_cache *fs_cachep;
/* SLAB cache for vm_area_struct structures */
static struct kmem_cache *vm_area_cachep;
/* SLAB cache for mm_struct structures (tsk->mm) */
static struct kmem_cache *mm_cachep;
struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
{
struct vm_area_struct *vma;
vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
if (vma)
vma_init(vma, mm);
return vma;
}
struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
{
struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
if (new) {
ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
/*
* orig->shared.rb may be modified concurrently, but the clone
* will be reinitialized.
*/
*new = data_race(*orig);
INIT_LIST_HEAD(&new->anon_vma_chain);
new->vm_next = new->vm_prev = NULL;
}
return new;
}
void vm_area_free(struct vm_area_struct *vma)
{
kmem_cache_free(vm_area_cachep, vma);
}
static void account_kernel_stack(struct task_struct *tsk, int account)
{
void *stack = task_stack_page(tsk);
struct vm_struct *vm = task_stack_vm_area(tsk);
if (vm) {
int i;
for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,
account * (PAGE_SIZE / 1024));
} else {
/* All stack pages are in the same node. */
mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB,
account * (THREAD_SIZE / 1024));
}
}
static int memcg_charge_kernel_stack(struct task_struct *tsk)
{
#ifdef CONFIG_VMAP_STACK
struct vm_struct *vm = task_stack_vm_area(tsk);
int ret;
BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
if (vm) {
int i;
BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
/*
* If memcg_kmem_charge_page() fails, page's
* memory cgroup pointer is NULL, and
* memcg_kmem_uncharge_page() in free_thread_stack()
* will ignore this page.
*/
ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL,
0);
if (ret)
return ret;
}
}
#endif
return 0;
}
static void release_task_stack(struct task_struct *tsk)
{
if (WARN_ON(tsk->state != TASK_DEAD))
return; /* Better to leak the stack than to free prematurely */
account_kernel_stack(tsk, -1);
free_thread_stack(tsk);
tsk->stack = NULL;
#ifdef CONFIG_VMAP_STACK
tsk->stack_vm_area = NULL;
#endif
}
#ifdef CONFIG_THREAD_INFO_IN_TASK
void put_task_stack(struct task_struct *tsk)
{
if (refcount_dec_and_test(&tsk->stack_refcount))
release_task_stack(tsk);
}
#endif
void free_task(struct task_struct *tsk)
{
scs_release(tsk);
#ifndef CONFIG_THREAD_INFO_IN_TASK
/*
* The task is finally done with both the stack and thread_info,
* so free both.
*/
release_task_stack(tsk);
#else
/*
* If the task had a separate stack allocation, it should be gone
* by now.
*/
WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
#endif
rt_mutex_debug_task_free(tsk);
ftrace_graph_exit_task(tsk);
arch_release_task_struct(tsk);
if (tsk->flags & PF_KTHREAD)
free_kthread_struct(tsk);
free_task_struct(tsk);
}
EXPORT_SYMBOL(free_task);
#ifdef CONFIG_MMU
static __latent_entropy int dup_mmap(struct mm_struct *mm,
struct mm_struct *oldmm)
{
struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
struct rb_node **rb_link, *rb_parent;
int retval;
unsigned long charge;
LIST_HEAD(uf);
uprobe_start_dup_mmap();
if (mmap_write_lock_killable(oldmm)) {
retval = -EINTR;
goto fail_uprobe_end;
}
flush_cache_dup_mm(oldmm);
uprobe_dup_mmap(oldmm, mm);
/*
* Not linked in yet - no deadlock potential:
*/
mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING);
/* No ordering required: file already has been exposed. */
RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
mm->total_vm = oldmm->total_vm;
mm->data_vm = oldmm->data_vm;
mm->exec_vm = oldmm->exec_vm;
mm->stack_vm = oldmm->stack_vm;
rb_link = &mm->mm_rb.rb_node;
rb_parent = NULL;
pprev = &mm->mmap;
retval = ksm_fork(mm, oldmm);
if (retval)
goto out;
retval = khugepaged_fork(mm, oldmm);
if (retval)
goto out;
prev = NULL;
for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
struct file *file;
if (mpnt->vm_flags & VM_DONTCOPY) {
vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
continue;
}
charge = 0;
/*
* Don't duplicate many vmas if we've been oom-killed (for
* example)
*/
if (fatal_signal_pending(current)) {
retval = -EINTR;
goto out;
}
if (mpnt->vm_flags & VM_ACCOUNT) {
unsigned long len = vma_pages(mpnt);
if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
goto fail_nomem;
charge = len;
}
tmp = vm_area_dup(mpnt);
if (!tmp)
goto fail_nomem;
retval = vma_dup_policy(mpnt, tmp);
if (retval)
goto fail_nomem_policy;
tmp->vm_mm = mm;
retval = dup_userfaultfd(tmp, &uf);
if (retval)
goto fail_nomem_anon_vma_fork;
if (tmp->vm_flags & VM_WIPEONFORK) {
/*
* VM_WIPEONFORK gets a clean slate in the child.
* Don't prepare anon_vma until fault since we don't
* copy page for current vma.
*/
tmp->anon_vma = NULL;
} else if (anon_vma_fork(tmp, mpnt))
goto fail_nomem_anon_vma_fork;
tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
file = tmp->vm_file;
if (file) {
struct inode *inode = file_inode(file);
struct address_space *mapping = file->f_mapping;
get_file(file);
if (tmp->vm_flags & VM_DENYWRITE)
put_write_access(inode);
i_mmap_lock_write(mapping);
if (tmp->vm_flags & VM_SHARED)
mapping_allow_writable(mapping);
flush_dcache_mmap_lock(mapping);
/* insert tmp into the share list, just after mpnt */
vma_interval_tree_insert_after(tmp, mpnt,
&mapping->i_mmap);
flush_dcache_mmap_unlock(mapping);
i_mmap_unlock_write(mapping);
}
/*
* Clear hugetlb-related page reserves for children. This only
* affects MAP_PRIVATE mappings. Faults generated by the child
* are not guaranteed to succeed, even if read-only
*/
if (is_vm_hugetlb_page(tmp))
reset_vma_resv_huge_pages(tmp);
/*
* Link in the new vma and copy the page table entries.
*/
*pprev = tmp;
pprev = &tmp->vm_next;
tmp->vm_prev = prev;
prev = tmp;
__vma_link_rb(mm, tmp, rb_link, rb_parent);
rb_link = &tmp->vm_rb.rb_right;
rb_parent = &tmp->vm_rb;
mm->map_count++;
if (!(tmp->vm_flags & VM_WIPEONFORK))
retval = copy_page_range(tmp, mpnt);
if (tmp->vm_ops && tmp->vm_ops->open)
tmp->vm_ops->open(tmp);
if (retval)
goto out;
}
/* a new mm has just been created */
retval = arch_dup_mmap(oldmm, mm);
out:
mmap_write_unlock(mm);
flush_tlb_mm(oldmm);
mmap_write_unlock(oldmm);
dup_userfaultfd_complete(&uf);
fail_uprobe_end:
uprobe_end_dup_mmap();
return retval;
fail_nomem_anon_vma_fork:
mpol_put(vma_policy(tmp));
fail_nomem_policy:
vm_area_free(tmp);
fail_nomem:
retval = -ENOMEM;
vm_unacct_memory(charge);
goto out;
}
static inline int mm_alloc_pgd(struct mm_struct *mm)
{
mm->pgd = pgd_alloc(mm);
if (unlikely(!mm->pgd))
return -ENOMEM;
return 0;
}
static inline void mm_free_pgd(struct mm_struct *mm)
{
pgd_free(mm, mm->pgd);
}
#else
static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
{
mmap_write_lock(oldmm);
RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
mmap_write_unlock(oldmm);
return 0;
}
#define mm_alloc_pgd(mm) (0)
#define mm_free_pgd(mm)
#endif /* CONFIG_MMU */
static void check_mm(struct mm_struct *mm)
{
int i;
BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
"Please make sure 'struct resident_page_types[]' is updated as well");
for (i = 0; i < NR_MM_COUNTERS; i++) {
long x = atomic_long_read(&mm->rss_stat.count[i]);
if (unlikely(x))
pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
mm, resident_page_types[i], x);
}
if (mm_pgtables_bytes(mm))
pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
mm_pgtables_bytes(mm));
#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
#endif
}
#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
/*
* Called when the last reference to the mm
* is dropped: either by a lazy thread or by
* mmput. Free the page directory and the mm.
*/
void __mmdrop(struct mm_struct *mm)
{
BUG_ON(mm == &init_mm);
WARN_ON_ONCE(mm == current->mm);
WARN_ON_ONCE(mm == current->active_mm);
mm_free_pgd(mm);
destroy_context(mm);
mmu_notifier_subscriptions_destroy(mm);
check_mm(mm);
put_user_ns(mm->user_ns);
free_mm(mm);
}
EXPORT_SYMBOL_GPL(__mmdrop);
static void mmdrop_async_fn(struct work_struct *work)
{
struct mm_struct *mm;
mm = container_of(work, struct mm_struct, async_put_work);
__mmdrop(mm);
}
static void mmdrop_async(struct mm_struct *mm)
{
if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
schedule_work(&mm->async_put_work);
}
}
static inline void free_signal_struct(struct signal_struct *sig)
{
taskstats_tgid_free(sig);
sched_autogroup_exit(sig);
/*
* __mmdrop is not safe to call from softirq context on x86 due to
* pgd_dtor so postpone it to the async context
*/
if (sig->oom_mm)
mmdrop_async(sig->oom_mm);
kmem_cache_free(signal_cachep, sig);
}
static inline void put_signal_struct(struct signal_struct *sig)
{
if (refcount_dec_and_test(&sig->sigcnt))
free_signal_struct(sig);
}
void __put_task_struct(struct task_struct *tsk)
{
WARN_ON(!tsk->exit_state);
WARN_ON(refcount_read(&tsk->usage));
WARN_ON(tsk == current);
io_uring_free(tsk);
cgroup_free(tsk);
task_numa_free(tsk, true);
security_task_free(tsk);
bpf_task_storage_free(tsk);
exit_creds(tsk);
delayacct_tsk_free(tsk);
put_signal_struct(tsk->signal);
if (!profile_handoff_task(tsk))
free_task(tsk);
}
EXPORT_SYMBOL_GPL(__put_task_struct);
void __init __weak arch_task_cache_init(void) { }
/*
* set_max_threads
*/
static void set_max_threads(unsigned int max_threads_suggested)
{
u64 threads;
unsigned long nr_pages = totalram_pages();
/*
* The number of threads shall be limited such that the thread
* structures may only consume a small part of the available memory.
*/
if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
threads = MAX_THREADS;
else
threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
(u64) THREAD_SIZE * 8UL);
if (threads > max_threads_suggested)
threads = max_threads_suggested;
max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
}
#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
/* Initialized by the architecture: */
int arch_task_struct_size __read_mostly;
#endif
#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
{
/* Fetch thread_struct whitelist for the architecture. */
arch_thread_struct_whitelist(offset, size);
/*
* Handle zero-sized whitelist or empty thread_struct, otherwise
* adjust offset to position of thread_struct in task_struct.
*/
if (unlikely(*size == 0))
*offset = 0;
else
*offset += offsetof(struct task_struct, thread);
}
#endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
void __init fork_init(void)
{
int i;
#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
#ifndef ARCH_MIN_TASKALIGN
#define ARCH_MIN_TASKALIGN 0
#endif
int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
unsigned long useroffset, usersize;
/* create a slab on which task_structs can be allocated */
task_struct_whitelist(&useroffset, &usersize);
task_struct_cachep = kmem_cache_create_usercopy("task_struct",
arch_task_struct_size, align,
SLAB_PANIC|SLAB_ACCOUNT,
useroffset, usersize, NULL);
#endif
/* do the arch specific task caches init */
arch_task_cache_init();
set_max_threads(MAX_THREADS);
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];
for (i = 0; i < UCOUNT_COUNTS; i++)
init_user_ns.ucount_max[i] = max_threads/2;
#ifdef CONFIG_VMAP_STACK
cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
NULL, free_vm_stack_cache);
#endif
scs_init();
lockdep_init_task(&init_task);
uprobes_init();
}
int __weak arch_dup_task_struct(struct task_struct *dst,
struct task_struct *src)
{
*dst = *src;
return 0;
}
void set_task_stack_end_magic(struct task_struct *tsk)
{
unsigned long *stackend;
stackend = end_of_stack(tsk);
*stackend = STACK_END_MAGIC; /* for overflow detection */
}
static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
{
struct task_struct *tsk;
unsigned long *stack;
struct vm_struct *stack_vm_area __maybe_unused;
int err;
if (node == NUMA_NO_NODE)
node = tsk_fork_get_node(orig);
tsk = alloc_task_struct_node(node);
if (!tsk)
return NULL;
stack = alloc_thread_stack_node(tsk, node);
if (!stack)
goto free_tsk;
if (memcg_charge_kernel_stack(tsk))
goto free_stack;
stack_vm_area = task_stack_vm_area(tsk);
err = arch_dup_task_struct(tsk, orig);
/*
* arch_dup_task_struct() clobbers the stack-related fields. Make
* sure they're properly initialized before using any stack-related
* functions again.
*/
tsk->stack = stack;
#ifdef CONFIG_VMAP_STACK
tsk->stack_vm_area = stack_vm_area;
#endif
#ifdef CONFIG_THREAD_INFO_IN_TASK
refcount_set(&tsk->stack_refcount, 1);
#endif
if (err)
goto free_stack;
err = scs_prepare(tsk, node);
if (err)
goto free_stack;
#ifdef CONFIG_SECCOMP
/*
* We must handle setting up seccomp filters once we're under
* the sighand lock in case orig has changed between now and
* then. Until then, filter must be NULL to avoid messing up
* the usage counts on the error path calling free_task.
*/
tsk->seccomp.filter = NULL;
#endif
setup_thread_stack(tsk, orig);
clear_user_return_notifier(tsk);
clear_tsk_need_resched(tsk);
set_task_stack_end_magic(tsk);
clear_syscall_work_syscall_user_dispatch(tsk);
#ifdef CONFIG_STACKPROTECTOR
tsk->stack_canary = get_random_canary();
#endif
if (orig->cpus_ptr == &orig->cpus_mask)
tsk->cpus_ptr = &tsk->cpus_mask;
/*
* One for the user space visible state that goes away when reaped.
* One for the scheduler.
*/
refcount_set(&tsk->rcu_users, 2);
/* One for the rcu users */
refcount_set(&tsk->usage, 1);
#ifdef CONFIG_BLK_DEV_IO_TRACE
tsk->btrace_seq = 0;
#endif
tsk->splice_pipe = NULL;
tsk->task_frag.page = NULL;
tsk->wake_q.next = NULL;
tsk->pf_io_worker = NULL;
account_kernel_stack(tsk, 1);
kcov_task_init(tsk);
kmap_local_fork(tsk);
#ifdef CONFIG_FAULT_INJECTION
tsk->fail_nth = 0;
#endif
#ifdef CONFIG_BLK_CGROUP
tsk->throttle_queue = NULL;
tsk->use_memdelay = 0;
#endif
#ifdef CONFIG_MEMCG
tsk->active_memcg = NULL;
#endif
return tsk;
free_stack:
free_thread_stack(tsk);
free_tsk:
free_task_struct(tsk);
return NULL;
}
__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
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);
#include <linux/init_task.h>
static void mm_init_aio(struct mm_struct *mm)
{
#ifdef CONFIG_AIO
spin_lock_init(&mm->ioctx_lock);
mm->ioctx_table = NULL;
#endif
}
static __always_inline void mm_clear_owner(struct mm_struct *mm,
struct task_struct *p)
{
#ifdef CONFIG_MEMCG
if (mm->owner == p)
WRITE_ONCE(mm->owner, NULL);
#endif
}
static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
{
#ifdef CONFIG_MEMCG
mm->owner = p;
#endif
}
static void mm_init_pasid(struct mm_struct *mm)
{
#ifdef CONFIG_IOMMU_SUPPORT
mm->pasid = INIT_PASID;
#endif
}
static void mm_init_uprobes_state(struct mm_struct *mm)
{
#ifdef CONFIG_UPROBES
mm->uprobes_state.xol_area = NULL;
#endif
}
static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
struct user_namespace *user_ns)
{
mm->mmap = NULL;
mm->mm_rb = RB_ROOT;
mm->vmacache_seqnum = 0;
atomic_set(&mm->mm_users, 1);
atomic_set(&mm->mm_count, 1);
seqcount_init(&mm->write_protect_seq);
mmap_init_lock(mm);
INIT_LIST_HEAD(&mm->mmlist);
mm->core_state = NULL;
mm_pgtables_bytes_init(mm);
mm->map_count = 0;
mm->locked_vm = 0;
atomic_set(&mm->has_pinned, 0);
atomic64_set(&mm->pinned_vm, 0);
memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
spin_lock_init(&mm->page_table_lock);
spin_lock_init(&mm->arg_lock);
mm_init_cpumask(mm);
mm_init_aio(mm);
mm_init_owner(mm, p);
mm_init_pasid(mm);
RCU_INIT_POINTER(mm->exe_file, NULL);
mmu_notifier_subscriptions_init(mm);
init_tlb_flush_pending(mm);
#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
mm->pmd_huge_pte = NULL;
#endif
mm_init_uprobes_state(mm);
if (current->mm) {
mm->flags = current->mm->flags & MMF_INIT_MASK;
mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
} else {
mm->flags = default_dump_filter;
mm->def_flags = 0;
}
if (mm_alloc_pgd(mm))
goto fail_nopgd;
if (init_new_context(p, mm))
goto fail_nocontext;
mm->user_ns = get_user_ns(user_ns);
return mm;
fail_nocontext:
mm_free_pgd(mm);
fail_nopgd:
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)
return NULL;
memset(mm, 0, sizeof(*mm));
return mm_init(mm, current, current_user_ns());
}
static inline void __mmput(struct mm_struct *mm)
{
VM_BUG_ON(atomic_read(&mm->mm_users));
uprobe_clear_state(mm);
exit_aio(mm);
ksm_exit(mm);
khugepaged_exit(mm); /* must run before exit_mmap */
exit_mmap(mm);
mm_put_huge_zero_page(mm);
set_mm_exe_file(mm, NULL);
if (!list_empty(&mm->mmlist)) {
spin_lock(&mmlist_lock);
list_del(&mm->mmlist);
spin_unlock(&mmlist_lock);
}
if (mm->binfmt)
module_put(mm->binfmt->module);
mmdrop(mm);
}
/*
* Decrement the use count and release all resources for an mm.
*/
void mmput(struct mm_struct *mm)
{
might_sleep();
if (atomic_dec_and_test(&mm->mm_users))
__mmput(mm);
}
EXPORT_SYMBOL_GPL(mmput);
#ifdef CONFIG_MMU
static void mmput_async_fn(struct work_struct *work)
{
struct mm_struct *mm = container_of(work, struct mm_struct,
async_put_work);
__mmput(mm);
}
void mmput_async(struct mm_struct *mm)
{
if (atomic_dec_and_test(&mm->mm_users)) {
INIT_WORK(&mm->async_put_work, mmput_async_fn);
schedule_work(&mm->async_put_work);
}
}
#endif
/**
* set_mm_exe_file - change a reference to the mm's executable file
*
* This changes mm's executable file (shown as symlink /proc/[pid]/exe).
*
* Main users are mmput() and sys_execve(). Callers prevent concurrent
* invocations: in mmput() nobody alive left, in execve task is single
* threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
* mm->exe_file, but does so without using set_mm_exe_file() in order
* to avoid the need for any locks.
*/
void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
{
struct file *old_exe_file;
/*
* It is safe to dereference the exe_file without RCU as
* this function is only called if nobody else can access
* this mm -- see comment above for justification.
*/
old_exe_file = rcu_dereference_raw(mm->exe_file);
if (new_exe_file)
get_file(new_exe_file);
rcu_assign_pointer(mm->exe_file, new_exe_file);
if (old_exe_file)
fput(old_exe_file);
}
/**
* get_mm_exe_file - acquire a reference to the mm's executable file
*
* Returns %NULL if mm has no associated executable file.
* User must release file via fput().
*/
struct file *get_mm_exe_file(struct mm_struct *mm)
{
struct file *exe_file;
rcu_read_lock();
exe_file = rcu_dereference(mm->exe_file);
if (exe_file && !get_file_rcu(exe_file))
exe_file = NULL;
rcu_read_unlock();
return exe_file;
}
EXPORT_SYMBOL(get_mm_exe_file);
/**
* get_task_exe_file - acquire a reference to the task's executable file
*
* Returns %NULL if task's mm (if any) has no associated executable file or
* this is a kernel thread with borrowed mm (see the comment above get_task_mm).
* User must release file via fput().
*/
struct file *get_task_exe_file(struct task_struct *task)
{
struct file *exe_file = NULL;
struct mm_struct *mm;
task_lock(task);
mm = task->mm;
if (mm) {
if (!(task->flags & PF_KTHREAD))
exe_file = get_mm_exe_file(mm);
}
task_unlock(task);
return exe_file;
}
EXPORT_SYMBOL(get_task_exe_file);
/**
* get_task_mm - acquire a reference to the task's mm
*
* Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
* 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) {
if (task->flags & PF_KTHREAD)
mm = NULL;
else
mmget(mm);
}
task_unlock(task);
return mm;
}
EXPORT_SYMBOL_GPL(get_task_mm);
struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
{
struct mm_struct *mm;
int err;
err = down_read_killable(&task->signal->exec_update_lock);
if (err)
return ERR_PTR(err);
mm = get_task_mm(task);
if (mm && mm != current->mm &&
!ptrace_may_access(task, mode)) {
mmput(mm);
mm = ERR_PTR(-EACCES);
}
up_read(&task->signal->exec_update_lock);
return mm;
}
static void complete_vfork_done(struct task_struct *tsk)
{
struct completion *vfork;
task_lock(tsk);
vfork = tsk->vfork_done;
if (likely(vfork)) {
tsk->vfork_done = NULL;
complete(vfork);
}
task_unlock(tsk);
}
static int wait_for_vfork_done(struct task_struct *child,
struct completion *vfork)
{
int killed;
freezer_do_not_count();
cgroup_enter_frozen();
killed = wait_for_completion_killable(vfork);
cgroup_leave_frozen(false);
freezer_count();
if (killed) {
task_lock(child);
child->vfork_done = NULL;
task_unlock(child);
}
put_task_struct(child);
return killed;
}
/* 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
*/
static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
{
uprobe_free_utask(tsk);
/* Get rid of any cached register state */
deactivate_mm(tsk, mm);
/*
* Signal userspace if we're not exiting with a core dump
* because we want to leave the value intact for debugging
* purposes.
*/
if (tsk->clear_child_tid) {
if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
atomic_read(&mm->mm_users) > 1) {
/*
* We don't check the error code - if userspace has
* not set up a proper pointer then tough luck.
*/
put_user(0, tsk->clear_child_tid);
do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1, NULL, NULL, 0, 0);
}
tsk->clear_child_tid = NULL;
}
/*
* All done, finally we can wake up parent and return this mm to him.
* Also kthread_stop() uses this completion for synchronization.
*/
if (tsk->vfork_done)
complete_vfork_done(tsk);
}
void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
{
futex_exit_release(tsk);
mm_release(tsk, mm);
}
void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
{
futex_exec_release(tsk);
mm_release(tsk, mm);
}
/**
* dup_mm() - duplicates an existing mm structure
* @tsk: the task_struct with which the new mm will be associated.
* @oldmm: the mm to duplicate.
*
* Allocates a new mm structure and duplicates the provided @oldmm structure
* content into it.
*
* Return: the duplicated mm or NULL on failure.
*/
static struct mm_struct *dup_mm(struct task_struct *tsk,
struct mm_struct *oldmm)
{
struct mm_struct *mm;
int err;
mm = allocate_mm();
if (!mm)
goto fail_nomem;
memcpy(mm, oldmm, sizeof(*mm));
if (!mm_init(mm, tsk, mm->user_ns))
goto fail_nomem;
err = dup_mmap(mm, oldmm);
if (err)
goto free_pt;
mm->hiwater_rss = get_mm_rss(mm);
mm->hiwater_vm = mm->total_vm;
if (mm->binfmt && !try_module_get(mm->binfmt->module))
goto free_pt;
return mm;
free_pt:
/* don't put binfmt in mmput, we haven't got module yet */
mm->binfmt = NULL;
mm_init_owner(mm, NULL);
mmput(mm);
fail_nomem:
return NULL;
}
static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
{
struct mm_struct *mm, *oldmm;
tsk->min_flt = tsk->maj_flt = 0;
tsk->nvcsw = tsk->nivcsw = 0;
#ifdef CONFIG_DETECT_HUNG_TASK
tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
tsk->last_switch_time = 0;
#endif
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;
/* initialize the new vmacache entries */
vmacache_flush(tsk);
if (clone_flags & CLONE_VM) {
mmget(oldmm);
mm = oldmm;
} else {
mm = dup_mm(tsk, current->mm);
if (!mm)
return -ENOMEM;
}
tsk->mm = mm;
tsk->active_mm = mm;
return 0;
}
static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
{
struct fs_struct *fs = current->fs;
if (clone_flags & CLONE_FS) {
/* tsk->fs is already what we want */
spin_lock(&fs->lock);
if (fs->in_exec) {
spin_unlock(&fs->lock);
return -EAGAIN;
}
fs->users++;
spin_unlock(&fs->lock);
return 0;
}
tsk->fs = copy_fs_struct(fs);
if (!tsk->fs)
return -ENOMEM;
return 0;
}
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, NR_OPEN_MAX, &error);
if (!newf)
goto out;
tsk->files = newf;
error = 0;
out:
return error;
}
static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
{
#ifdef CONFIG_BLOCK
struct io_context *ioc = current->io_context;
struct io_context *new_ioc;
if (!ioc)
return 0;
/*
* Share io context with parent, if CLONE_IO is set
*/
if (clone_flags & CLONE_IO) {
ioc_task_link(ioc);
tsk->io_context = ioc;
} else if (ioprio_valid(ioc->ioprio)) {
new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
if (unlikely(!new_ioc))
return -ENOMEM;
new_ioc->ioprio = ioc->ioprio;
put_io_context(new_ioc);
}
#endif
return 0;
}
static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
{
struct sighand_struct *sig;
if (clone_flags & CLONE_SIGHAND) {
refcount_inc(&current->sighand->count);
return 0;
}
sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
RCU_INIT_POINTER(tsk->sighand, sig);
if (!sig)
return -ENOMEM;
refcount_set(&sig->count, 1);
spin_lock_irq(&current->sighand->siglock);
memcpy(sig->action, current->sighand->action, sizeof(sig->action));
spin_unlock_irq(&current->sighand->siglock);
/* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
if (clone_flags & CLONE_CLEAR_SIGHAND)
flush_signal_handlers(tsk, 0);
return 0;
}
void __cleanup_sighand(struct sighand_struct *sighand)
{
if (refcount_dec_and_test(&sighand->count)) {
signalfd_cleanup(sighand);
/*
* sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
* without an RCU grace period, see __lock_task_sighand().
*/
kmem_cache_free(sighand_cachep, sighand);
}
}
/*
* Initialize POSIX timer handling for a thread group.
*/
static void posix_cpu_timers_init_group(struct signal_struct *sig)
{
struct posix_cputimers *pct = &sig->posix_cputimers;
unsigned long cpu_limit;
cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
posix_cputimers_group_init(pct, cpu_limit);
}
static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
{
struct signal_struct *sig;
if (clone_flags & CLONE_THREAD)
return 0;
sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
tsk->signal = sig;
if (!sig)
return -ENOMEM;
sig->nr_threads = 1;
atomic_set(&sig->live, 1);
refcount_set(&sig->sigcnt, 1);
/* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
init_waitqueue_head(&sig->wait_chldexit);
sig->curr_target = tsk;
init_sigpending(&sig->shared_pending);
INIT_HLIST_HEAD(&sig->multiprocess);
seqlock_init(&sig->stats_lock);
prev_cputime_init(&sig->prev_cputime);
#ifdef CONFIG_POSIX_TIMERS
INIT_LIST_HEAD(&sig->posix_timers);
hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
sig->real_timer.function = it_real_fn;
#endif
task_lock(current->group_leader);
memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
task_unlock(current->group_leader);
posix_cpu_timers_init_group(sig);
tty_audit_fork(sig);
sched_autogroup_fork(sig);
sig->oom_score_adj = current->signal->oom_score_adj;
sig->oom_score_adj_min = current->signal->oom_score_adj_min;
mutex_init(&sig->cred_guard_mutex);
init_rwsem(&sig->exec_update_lock);
return 0;
}
static void copy_seccomp(struct task_struct *p)
{
#ifdef CONFIG_SECCOMP
/*
* Must be called with sighand->lock held, which is common to
* all threads in the group. Holding cred_guard_mutex is not
* needed because this new task is not yet running and cannot
* be racing exec.
*/
assert_spin_locked(&current->sighand->siglock);
/* Ref-count the new filter user, and assign it. */
get_seccomp_filter(current);
p->seccomp = current->seccomp;
/*
* Explicitly enable no_new_privs here in case it got set
* between the task_struct being duplicated and holding the
* sighand lock. The seccomp state and nnp must be in sync.
*/
if (task_no_new_privs(current))
task_set_no_new_privs(p);
/*
* If the parent gained a seccomp mode after copying thread
* flags and between before we held the sighand lock, we have
* to manually enable the seccomp thread flag here.
*/
if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
set_task_syscall_work(p, SECCOMP);
#endif
}
SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
{
current->clear_child_tid = tidptr;
return task_pid_vnr(current);
}
static void rt_mutex_init_task(struct task_struct *p)
{
raw_spin_lock_init(&p->pi_lock);
#ifdef CONFIG_RT_MUTEXES
p->pi_waiters = RB_ROOT_CACHED;
p->pi_top_task = NULL;
p->pi_blocked_on = NULL;
#endif
}
static inline void init_task_pid_links(struct task_struct *task)
{
enum pid_type type;
for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type)
INIT_HLIST_NODE(&task->pid_links[type]);
}
static inline void
init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
{
if (type == PIDTYPE_PID)
task->thread_pid = pid;
else
task->signal->pids[type] = pid;
}
static inline void rcu_copy_process(struct task_struct *p)
{
#ifdef CONFIG_PREEMPT_RCU
p->rcu_read_lock_nesting = 0;
p->rcu_read_unlock_special.s = 0;
p->rcu_blocked_node = NULL;
INIT_LIST_HEAD(&p->rcu_node_entry);
#endif /* #ifdef CONFIG_PREEMPT_RCU */
#ifdef CONFIG_TASKS_RCU
p->rcu_tasks_holdout = false;
INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
p->rcu_tasks_idle_cpu = -1;
#endif /* #ifdef CONFIG_TASKS_RCU */
#ifdef CONFIG_TASKS_TRACE_RCU
p->trc_reader_nesting = 0;
p->trc_reader_special.s = 0;
INIT_LIST_HEAD(&p->trc_holdout_list);
#endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
}
struct pid *pidfd_pid(const struct file *file)
{
if (file->f_op == &pidfd_fops)
return file->private_data;
return ERR_PTR(-EBADF);
}
static int pidfd_release(struct inode *inode, struct file *file)
{
struct pid *pid = file->private_data;
file->private_data = NULL;
put_pid(pid);
return 0;
}
#ifdef CONFIG_PROC_FS
/**
* pidfd_show_fdinfo - print information about a pidfd
* @m: proc fdinfo file
* @f: file referencing a pidfd
*
* Pid:
* This function will print the pid that a given pidfd refers to in the
* pid namespace of the procfs instance.
* If the pid namespace of the process is not a descendant of the pid
* namespace of the procfs instance 0 will be shown as its pid. This is
* similar to calling getppid() on a process whose parent is outside of
* its pid namespace.
*
* NSpid:
* If pid namespaces are supported then this function will also print
* the pid of a given pidfd refers to for all descendant pid namespaces
* starting from the current pid namespace of the instance, i.e. the
* Pid field and the first entry in the NSpid field will be identical.
* If the pid namespace of the process is not a descendant of the pid
* namespace of the procfs instance 0 will be shown as its first NSpid
* entry and no others will be shown.
* Note that this differs from the Pid and NSpid fields in
* /proc/<pid>/status where Pid and NSpid are always shown relative to
* the pid namespace of the procfs instance. The difference becomes
* obvious when sending around a pidfd between pid namespaces from a
* different branch of the tree, i.e. where no ancestral relation is
* present between the pid namespaces:
* - create two new pid namespaces ns1 and ns2 in the initial pid
* namespace (also take care to create new mount namespaces in the
* new pid namespace and mount procfs)
* - create a process with a pidfd in ns1
* - send pidfd from ns1 to ns2
* - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
* have exactly one entry, which is 0
*/
static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
{
struct pid *pid = f->private_data;
struct pid_namespace *ns;
pid_t nr = -1;
if (likely(pid_has_task(pid, PIDTYPE_PID))) {
ns = proc_pid_ns(file_inode(m->file)->i_sb);
nr = pid_nr_ns(pid, ns);
}
seq_put_decimal_ll(m, "Pid:\t", nr);
#ifdef CONFIG_PID_NS
seq_put_decimal_ll(m, "\nNSpid:\t", nr);
if (nr > 0) {
int i;
/* If nr is non-zero it means that 'pid' is valid and that
* ns, i.e. the pid namespace associated with the procfs
* instance, is in the pid namespace hierarchy of pid.
* Start at one below the already printed level.
*/
for (i = ns->level + 1; i <= pid->level; i++)
seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
}
#endif
seq_putc(m, '\n');
}
#endif
/*
* Poll support for process exit notification.
*/
static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
{
struct pid *pid = file->private_data;
__poll_t poll_flags = 0;
poll_wait(file, &pid->wait_pidfd, pts);
/*
* Inform pollers only when the whole thread group exits.
* If the thread group leader exits before all other threads in the
* group, then poll(2) should block, similar to the wait(2) family.
*/
if (thread_group_exited(pid))
poll_flags = EPOLLIN | EPOLLRDNORM;
return poll_flags;
}
const struct file_operations pidfd_fops = {
.release = pidfd_release,
.poll = pidfd_poll,
#ifdef CONFIG_PROC_FS
.show_fdinfo = pidfd_show_fdinfo,
#endif
};
static void __delayed_free_task(struct rcu_head *rhp)
{
struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
free_task(tsk);
}
static __always_inline void delayed_free_task(struct task_struct *tsk)
{
if (IS_ENABLED(CONFIG_MEMCG))
call_rcu(&tsk->rcu, __delayed_free_task);
else
free_task(tsk);
}
static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk)
{
/* Skip if kernel thread */
if (!tsk->mm)
return;
/* Skip if spawning a thread or using vfork */
if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM)
return;
/* We need to synchronize with __set_oom_adj */
mutex_lock(&oom_adj_mutex);
set_bit(MMF_MULTIPROCESS, &tsk->mm->flags);
/* Update the values in case they were changed after copy_signal */
tsk->signal->oom_score_adj = current->signal->oom_score_adj;
tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min;
mutex_unlock(&oom_adj_mutex);
}
/*
* 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.
*/
static __latent_entropy struct task_struct *copy_process(
struct pid *pid,
int trace,
int node,
struct kernel_clone_args *args)
{
int pidfd = -1, retval;
struct task_struct *p;
struct multiprocess_signals delayed;
struct file *pidfile = NULL;
u64 clone_flags = args->flags;
struct nsproxy *nsp = current->nsproxy;
/*
* Don't allow sharing the root directory with processes in a different
* namespace
*/
if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
return ERR_PTR(-EINVAL);
if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|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);
/*
* Siblings of global init remain as zombies on exit since they are
* not reaped by their parent (swapper). To solve this and to avoid
* multi-rooted process trees, prevent global and container-inits
* from creating siblings.
*/
if ((clone_flags & CLONE_PARENT) &&
current->signal->flags & SIGNAL_UNKILLABLE)
return ERR_PTR(-EINVAL);
/*
* If the new process will be in a different pid or user namespace
* do not allow it to share a thread group with the forking task.
*/
if (clone_flags & CLONE_THREAD) {
if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
(task_active_pid_ns(current) != nsp->pid_ns_for_children))
return ERR_PTR(-EINVAL);
}
/*
* If the new process will be in a different time namespace
* do not allow it to share VM or a thread group with the forking task.
*/
if (clone_flags & (CLONE_THREAD | CLONE_VM)) {
if (nsp->time_ns != nsp->time_ns_for_children)
return ERR_PTR(-EINVAL);
}
if (clone_flags & CLONE_PIDFD) {
/*
* - CLONE_DETACHED is blocked so that we can potentially
* reuse it later for CLONE_PIDFD.
* - CLONE_THREAD is blocked until someone really needs it.
*/
if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
return ERR_PTR(-EINVAL);
}
/*
* Force any signals received before this point to be delivered
* before the fork happens. Collect up signals sent to multiple
* processes that happen during the fork and delay them so that
* they appear to happen after the fork.
*/
sigemptyset(&delayed.signal);
INIT_HLIST_NODE(&delayed.node);
spin_lock_irq(&current->sighand->siglock);
if (!(clone_flags & CLONE_THREAD))
hlist_add_head(&delayed.node, &current->signal->multiprocess);
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
retval = -ERESTARTNOINTR;
if (task_sigpending(current))
goto fork_out;
retval = -ENOMEM;
p = dup_task_struct(current, node);
if (!p)
goto fork_out;
if (args->io_thread) {
/*
* Mark us an IO worker, and block any signal that isn't
* fatal or STOP
*/
p->flags |= PF_IO_WORKER;
siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
}
/*
* This _must_ happen before we call free_task(), i.e. before we jump
* to any of the bad_fork_* labels. This is to avoid freeing
* p->set_child_tid which is (ab)used as a kthread's data pointer for
* kernel threads (PF_KTHREAD).
*/
p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
/*
* Clear TID on mm_release()?
*/
p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
ftrace_graph_init_task(p);
rt_mutex_init_task(p);
lockdep_assert_irqs_enabled();
#ifdef CONFIG_PROVE_LOCKING
DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
#endif
retval = -EAGAIN;
if (atomic_read(&p->real_cred->user->processes) >=
task_rlimit(p, RLIMIT_NPROC)) {
if (p->real_cred->user != INIT_USER &&
!capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
goto bad_fork_free;
}
current->flags &= ~PF_NPROC_EXCEEDED;
retval = copy_creds(p, clone_flags);
if (retval < 0)
goto bad_fork_free;
/*
* 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.
*/
retval = -EAGAIN;
if (data_race(nr_threads >= max_threads))
goto bad_fork_cleanup_count;
delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
p->flags |= PF_FORKNOEXEC;
INIT_LIST_HEAD(&p->children);
INIT_LIST_HEAD(&p->sibling);
rcu_copy_process(p);
p->vfork_done = NULL;
spin_lock_init(&p->alloc_lock);
init_sigpending(&p->pending);
p->utime = p->stime = p->gtime = 0;
#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
p->utimescaled = p->stimescaled = 0;
#endif
prev_cputime_init(&p->prev_cputime);
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
seqcount_init(&p->vtime.seqcount);
p->vtime.starttime = 0;
p->vtime.state = VTIME_INACTIVE;
#endif
#ifdef CONFIG_IO_URING
p->io_uring = NULL;
#endif
#if defined(SPLIT_RSS_COUNTING)
memset(&p->rss_stat, 0, sizeof(p->rss_stat));
#endif
p->default_timer_slack_ns = current->timer_slack_ns;
#ifdef CONFIG_PSI
p->psi_flags = 0;
#endif
task_io_accounting_init(&p->ioac);
acct_clear_integrals(p);
posix_cputimers_init(&p->posix_cputimers);
p->io_context = NULL;
audit_set_context(p, NULL);
cgroup_fork(p);
#ifdef CONFIG_NUMA
p->mempolicy = mpol_dup(p->mempolicy);
if (IS_ERR(p->mempolicy)) {
retval = PTR_ERR(p->mempolicy);
p->mempolicy = NULL;
goto bad_fork_cleanup_threadgroup_lock;
}
#endif
#ifdef CONFIG_CPUSETS
p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
#endif
#ifdef CONFIG_TRACE_IRQFLAGS
memset(&p->irqtrace, 0, sizeof(p->irqtrace));
p->irqtrace.hardirq_disable_ip = _THIS_IP_;
p->irqtrace.softirq_enable_ip = _THIS_IP_;
p->softirqs_enabled = 1;
p->softirq_context = 0;
#endif
p->pagefault_disabled = 0;
#ifdef CONFIG_LOCKDEP
lockdep_init_task(p);
#endif
#ifdef CONFIG_DEBUG_MUTEXES
p->blocked_on = NULL; /* not blocked yet */
#endif
#ifdef CONFIG_BCACHE
p->sequential_io = 0;
p->sequential_io_avg = 0;
#endif
#ifdef CONFIG_BPF_SYSCALL
RCU_INIT_POINTER(p->bpf_storage, NULL);
#endif
/* Perform scheduler related setup. Assign this task to a CPU. */
retval = sched_fork(clone_flags, p);
if (retval)
goto bad_fork_cleanup_policy;
retval = perf_event_init_task(p, clone_flags);
if (retval)
goto bad_fork_cleanup_policy;
retval = audit_alloc(p);
if (retval)
goto bad_fork_cleanup_perf;
/* copy all the process information */
shm_init_task(p);
retval = security_task_alloc(p, clone_flags);
if (retval)
goto bad_fork_cleanup_audit;
retval = copy_semundo(clone_flags, p);
if (retval)
goto bad_fork_cleanup_security;
retval = copy_files(clone_flags, p);
if (retval)
goto bad_fork_cleanup_semundo;
retval = copy_fs(clone_flags, p);
if (retval)
goto bad_fork_cleanup_files;
retval = copy_sighand(clone_flags, p);
if (retval)
goto bad_fork_cleanup_fs;
retval = copy_signal(clone_flags, p);
if (retval)
goto bad_fork_cleanup_sighand;
retval = copy_mm(clone_flags, p);
if (retval)
goto bad_fork_cleanup_signal;
retval = copy_namespaces(clone_flags, p);
if (retval)
goto bad_fork_cleanup_mm;
retval = copy_io(clone_flags, p);
if (retval)
goto bad_fork_cleanup_namespaces;
retval = copy_thread(clone_flags, args->stack, args->stack_size, p, args->tls);
if (retval)
goto bad_fork_cleanup_io;
stackleak_task_init(p);
if (pid != &init_struct_pid) {
pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
args->set_tid_size);
if (IS_ERR(pid)) {
retval = PTR_ERR(pid);
goto bad_fork_cleanup_thread;
}
}
/*
* This has to happen after we've potentially unshared the file
* descriptor table (so that the pidfd doesn't leak into the child
* if the fd table isn't shared).
*/
if (clone_flags & CLONE_PIDFD) {
retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
if (retval < 0)
goto bad_fork_free_pid;
pidfd = retval;
pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
O_RDWR | O_CLOEXEC);
if (IS_ERR(pidfile)) {
put_unused_fd(pidfd);
retval = PTR_ERR(pidfile);
goto bad_fork_free_pid;
}
get_pid(pid); /* held by pidfile now */
retval = put_user(pidfd, args->pidfd);
if (retval)
goto bad_fork_put_pidfd;
}
#ifdef CONFIG_BLOCK
p->plug = NULL;
#endif
futex_init_task(p);
/*
* sigaltstack should be cleared when sharing the same VM
*/
if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
sas_ss_reset(p);
/*
* Syscall tracing and stepping should be turned off in the
* child regardless of CLONE_PTRACE.
*/
user_disable_single_step(p);
clear_task_syscall_work(p, SYSCALL_TRACE);
#if defined(CONFIG_GENERIC_ENTRY) || defined(TIF_SYSCALL_EMU)
clear_task_syscall_work(p, SYSCALL_EMU);
#endif
clear_tsk_latency_tracing(p);
/* ok, now we should be set up.. */
p->pid = pid_nr(pid);
if (clone_flags & CLONE_THREAD) {
p->group_leader = current->group_leader;
p->tgid = current->tgid;
} else {
p->group_leader = p;
p->tgid = p->pid;
}
p->nr_dirtied = 0;
p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
p->dirty_paused_when = 0;
p->pdeath_signal = 0;
INIT_LIST_HEAD(&p->thread_group);
p->task_works = NULL;
#ifdef CONFIG_KRETPROBES
p->kretprobe_instances.first = NULL;
#endif
/*
* Ensure that the cgroup subsystem policies allow the new process to be
* forked. It should be noted that the new process's css_set can be changed
* between here and cgroup_post_fork() if an organisation operation is in
* progress.
*/
retval = cgroup_can_fork(p, args);
if (retval)
goto bad_fork_put_pidfd;
/*
* From this point on we must avoid any synchronous user-space
* communication until we take the tasklist-lock. In particular, we do
* not want user-space to be able to predict the process start-time by
* stalling fork(2) after we recorded the start_time but before it is
* visible to the system.
*/
p->start_time = ktime_get_ns();
p->start_boottime = ktime_get_boottime_ns();
/*
* Make it visible to the rest of the system, but dont wake it up yet.
* Need tasklist lock for parent etc handling!
*/
write_lock_irq(&tasklist_lock);
/* CLONE_PARENT re-uses the old parent */
if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
p->real_parent = current->real_parent;
p->parent_exec_id = current->parent_exec_id;
if (clone_flags & CLONE_THREAD)
p->exit_signal = -1;
else
p->exit_signal = current->group_leader->exit_signal;
} else {
p->real_parent = current;
p->parent_exec_id = current->self_exec_id;
p->exit_signal = args->exit_signal;
}
klp_copy_process(p);
spin_lock(&current->sighand->siglock);
/*
* Copy seccomp details explicitly here, in case they were changed
* before holding sighand lock.
*/
copy_seccomp(p);
rseq_fork(p, clone_flags);
/* Don't start children in a dying pid namespace */
if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
retval = -ENOMEM;
goto bad_fork_cancel_cgroup;
}
/* Let kill terminate clone/fork in the middle */
if (fatal_signal_pending(current)) {
retval = -EINTR;
goto bad_fork_cancel_cgroup;
}
/* past the last point of failure */
if (pidfile)
fd_install(pidfd, pidfile);
init_task_pid_links(p);
if (likely(p->pid)) {
ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
init_task_pid(p, PIDTYPE_PID, pid);
if (thread_group_leader(p)) {
init_task_pid(p, PIDTYPE_TGID, pid);
init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
init_task_pid(p, PIDTYPE_SID, task_session(current));
if (is_child_reaper(pid)) {
ns_of_pid(pid)->child_reaper = p;
p->signal->flags |= SIGNAL_UNKILLABLE;
}
p->signal->shared_pending.signal = delayed.signal;
p->signal->tty = tty_kref_get(current->signal->tty);
/*
* Inherit has_child_subreaper flag under the same
* tasklist_lock with adding child to the process tree
* for propagate_has_child_subreaper optimization.
*/
p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
p->real_parent->signal->is_child_subreaper;
list_add_tail(&p->sibling, &p->real_parent->children);
list_add_tail_rcu(&p->tasks, &init_task.tasks);
attach_pid(p, PIDTYPE_TGID);
attach_pid(p, PIDTYPE_PGID);
attach_pid(p, PIDTYPE_SID);
__this_cpu_inc(process_counts);
} else {
current->signal->nr_threads++;
atomic_inc(&current->signal->live);
refcount_inc(&current->signal->sigcnt);
task_join_group_stop(p);
list_add_tail_rcu(&p->thread_group,
&p->group_leader->thread_group);
list_add_tail_rcu(&p->thread_node,
&p->signal->thread_head);
}
attach_pid(p, PIDTYPE_PID);
nr_threads++;
}
total_forks++;
hlist_del_init(&delayed.node);
spin_unlock(&current->sighand->siglock);
syscall_tracepoint_update(p);
write_unlock_irq(&tasklist_lock);
proc_fork_connector(p);
sched_post_fork(p);
cgroup_post_fork(p, args);
perf_event_fork(p);
trace_task_newtask(p, clone_flags);
uprobe_copy_process(p, clone_flags);
copy_oom_score_adj(clone_flags, p);
return p;
bad_fork_cancel_cgroup:
spin_unlock(&current->sighand->siglock);
write_unlock_irq(&tasklist_lock);
cgroup_cancel_fork(p, args);
bad_fork_put_pidfd:
if (clone_flags & CLONE_PIDFD) {
fput(pidfile);
put_unused_fd(pidfd);
}
bad_fork_free_pid:
if (pid != &init_struct_pid)
free_pid(pid);
bad_fork_cleanup_thread:
exit_thread(p);
bad_fork_cleanup_io:
if (p->io_context)
exit_io_context(p);
bad_fork_cleanup_namespaces:
exit_task_namespaces(p);
bad_fork_cleanup_mm:
if (p->mm) {
mm_clear_owner(p->mm, p);
mmput(p->mm);
}
bad_fork_cleanup_signal:
if (!(clone_flags & CLONE_THREAD))
free_signal_struct(p->signal);
bad_fork_cleanup_sighand:
__cleanup_sighand(p->sighand);
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_security:
security_task_free(p);
bad_fork_cleanup_audit:
audit_free(p);
bad_fork_cleanup_perf:
perf_event_free_task(p);
bad_fork_cleanup_policy:
lockdep_free_task(p);
#ifdef CONFIG_NUMA
mpol_put(p->mempolicy);
bad_fork_cleanup_threadgroup_lock:
#endif
delayacct_tsk_free(p);
bad_fork_cleanup_count:
atomic_dec(&p->cred->user->processes);
exit_creds(p);
bad_fork_free:
p->state = TASK_DEAD;
put_task_stack(p);
delayed_free_task(p);
fork_out:
spin_lock_irq(&current->sighand->siglock);
hlist_del_init(&delayed.node);
spin_unlock_irq(&current->sighand->siglock);
return ERR_PTR(retval);
}
static inline void init_idle_pids(struct task_struct *idle)
{
enum pid_type type;
for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
init_task_pid(idle, type, &init_struct_pid);
}
}
struct task_struct *fork_idle(int cpu)
{
struct task_struct *task;
struct kernel_clone_args args = {
.flags = CLONE_VM,
};
task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
if (!IS_ERR(task)) {
init_idle_pids(task);
init_idle(task, cpu);
}
return task;
}
struct mm_struct *copy_init_mm(void)
{
return dup_mm(NULL, &init_mm);
}
/*
* This is like kernel_clone(), but shaved down and tailored to just
* creating io_uring workers. It returns a created task, or an error pointer.
* The returned task is inactive, and the caller must fire it up through
* wake_up_new_task(p). All signals are blocked in the created task.
*/
struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
{
unsigned long flags = CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|
CLONE_IO;
struct kernel_clone_args args = {
.flags = ((lower_32_bits(flags) | CLONE_VM |
CLONE_UNTRACED) & ~CSIGNAL),
.exit_signal = (lower_32_bits(flags) & CSIGNAL),
.stack = (unsigned long)fn,
.stack_size = (unsigned long)arg,
.io_thread = 1,
};
return copy_process(NULL, 0, node, &args);
}
/*
* 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.
*
* args->exit_signal is expected to be checked for sanity by the caller.
*/
pid_t kernel_clone(struct kernel_clone_args *args)
{
u64 clone_flags = args->flags;
struct completion vfork;
struct pid *pid;
struct task_struct *p;
int trace = 0;
pid_t nr;
/*
* For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
* to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
* mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
* field in struct clone_args and it still doesn't make sense to have
* them both point at the same memory location. Performing this check
* here has the advantage that we don't need to have a separate helper
* to check for legacy clone().
*/
if ((args->flags & CLONE_PIDFD) &&
(args->flags & CLONE_PARENT_SETTID) &&
(args->pidfd == args->parent_tid))
return -EINVAL;
/*
* Determine whether and which event to report to ptracer. When
* called from kernel_thread or CLONE_UNTRACED is explicitly
* requested, no event is reported; otherwise, report if the event
* for the type of forking is enabled.
*/
if (!(clone_flags & CLONE_UNTRACED)) {
if (clone_flags & CLONE_VFORK)
trace = PTRACE_EVENT_VFORK;
else if (args->exit_signal != SIGCHLD)
trace = PTRACE_EVENT_CLONE;
else
trace = PTRACE_EVENT_FORK;
if (likely(!ptrace_event_enabled(current, trace)))
trace = 0;
}
p = copy_process(NULL, trace, NUMA_NO_NODE, args);
add_latent_entropy();
if (IS_ERR(p))
return PTR_ERR(p);
/*
* Do this prior waking up the new thread - the thread pointer
* might get invalid after that point, if the thread exits quickly.
*/
trace_sched_process_fork(current, p);
pid = get_task_pid(p, PIDTYPE_PID);
nr = pid_vnr(pid);
if (clone_flags & CLONE_PARENT_SETTID)
put_user(nr, args->parent_tid);
if (clone_flags & CLONE_VFORK) {
p->vfork_done = &vfork;
init_completion(&vfork);
get_task_struct(p);
}
wake_up_new_task(p);
/* forking complete and child started to run, tell ptracer */
if (unlikely(trace))
ptrace_event_pid(trace, pid);
if (clone_flags & CLONE_VFORK) {
if (!wait_for_vfork_done(p, &vfork))
ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
}
put_pid(pid);
return nr;
}
/*
* Create a kernel thread.
*/
pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
{
struct kernel_clone_args args = {
.flags = ((lower_32_bits(flags) | CLONE_VM |
CLONE_UNTRACED) & ~CSIGNAL),
.exit_signal = (lower_32_bits(flags) & CSIGNAL),
.stack = (unsigned long)fn,
.stack_size = (unsigned long)arg,
};
return kernel_clone(&args);
}
#ifdef __ARCH_WANT_SYS_FORK
SYSCALL_DEFINE0(fork)
{
#ifdef CONFIG_MMU
struct kernel_clone_args args = {
.exit_signal = SIGCHLD,
};
return kernel_clone(&args);
#else
/* can not support in nommu mode */
return -EINVAL;
#endif
}
#endif
#ifdef __ARCH_WANT_SYS_VFORK
SYSCALL_DEFINE0(vfork)
{
struct kernel_clone_args args = {
.flags = CLONE_VFORK | CLONE_VM,
.exit_signal = SIGCHLD,
};
return kernel_clone(&args);
}
#endif
#ifdef __ARCH_WANT_SYS_CLONE
#ifdef CONFIG_CLONE_BACKWARDS
SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
int __user *, parent_tidptr,
unsigned long, tls,
int __user *, child_tidptr)
#elif defined(CONFIG_CLONE_BACKWARDS2)
SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
int __user *, parent_tidptr,
int __user *, child_tidptr,
unsigned long, tls)
#elif defined(CONFIG_CLONE_BACKWARDS3)
SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
int, stack_size,
int __user *, parent_tidptr,
int __user *, child_tidptr,
unsigned long, tls)
#else
SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
int __user *, parent_tidptr,
int __user *, child_tidptr,
unsigned long, tls)
#endif
{
struct kernel_clone_args args = {
.flags = (lower_32_bits(clone_flags) & ~CSIGNAL),
.pidfd = parent_tidptr,
.child_tid = child_tidptr,
.parent_tid = parent_tidptr,
.exit_signal = (lower_32_bits(clone_flags) & CSIGNAL),
.stack = newsp,
.tls = tls,
};
return kernel_clone(&args);
}
#endif
#ifdef __ARCH_WANT_SYS_CLONE3
noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
struct clone_args __user *uargs,
size_t usize)
{
int err;
struct clone_args args;
pid_t *kset_tid = kargs->set_tid;
BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
CLONE_ARGS_SIZE_VER0);
BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
CLONE_ARGS_SIZE_VER1);
BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
CLONE_ARGS_SIZE_VER2);
BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
if (unlikely(usize > PAGE_SIZE))
return -E2BIG;
if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
return -EINVAL;
err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
if (err)
return err;
if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
return -EINVAL;
if (unlikely(!args.set_tid && args.set_tid_size > 0))
return -EINVAL;
if (unlikely(args.set_tid && args.set_tid_size == 0))
return -EINVAL;
/*
* Verify that higher 32bits of exit_signal are unset and that
* it is a valid signal
*/
if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
!valid_signal(args.exit_signal)))
return -EINVAL;
if ((args.flags & CLONE_INTO_CGROUP) &&
(args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
return -EINVAL;
*kargs = (struct kernel_clone_args){
.flags = args.flags,
.pidfd = u64_to_user_ptr(args.pidfd),
.child_tid = u64_to_user_ptr(args.child_tid),
.parent_tid = u64_to_user_ptr(args.parent_tid),
.exit_signal = args.exit_signal,
.stack = args.stack,
.stack_size = args.stack_size,
.tls = args.tls,
.set_tid_size = args.set_tid_size,
.cgroup = args.cgroup,
};
if (args.set_tid &&
copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
(kargs->set_tid_size * sizeof(pid_t))))
return -EFAULT;
kargs->set_tid = kset_tid;
return 0;
}
/**
* clone3_stack_valid - check and prepare stack
* @kargs: kernel clone args
*
* Verify that the stack arguments userspace gave us are sane.
* In addition, set the stack direction for userspace since it's easy for us to
* determine.
*/
static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
{
if (kargs->stack == 0) {
if (kargs->stack_size > 0)
return false;
} else {
if (kargs->stack_size == 0)
return false;
if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
return false;
#if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
kargs->stack += kargs->stack_size;
#endif
}
return true;
}
static bool clone3_args_valid(struct kernel_clone_args *kargs)
{
/* Verify that no unknown flags are passed along. */
if (kargs->flags &
~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
return false;
/*
* - make the CLONE_DETACHED bit reusable for clone3
* - make the CSIGNAL bits reusable for clone3
*/
if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
return false;
if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
(CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
return false;
if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
kargs->exit_signal)
return false;
if (!clone3_stack_valid(kargs))
return false;
return true;
}
/**
* clone3 - create a new process with specific properties
* @uargs: argument structure
* @size: size of @uargs
*
* clone3() is the extensible successor to clone()/clone2().
* It takes a struct as argument that is versioned by its size.
*
* Return: On success, a positive PID for the child process.
* On error, a negative errno number.
*/
SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
{
int err;
struct kernel_clone_args kargs;
pid_t set_tid[MAX_PID_NS_LEVEL];
kargs.set_tid = set_tid;
err = copy_clone_args_from_user(&kargs, uargs, size);
if (err)
return err;
if (!clone3_args_valid(&kargs))
return -EINVAL;
return kernel_clone(&kargs);
}
#endif
void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
{
struct task_struct *leader, *parent, *child;
int res;
read_lock(&tasklist_lock);
leader = top = top->group_leader;
down:
for_each_thread(leader, parent) {
list_for_each_entry(child, &parent->children, sibling) {
res = visitor(child, data);
if (res) {
if (res < 0)
goto out;
leader = child;
goto down;
}
up:
;
}
}
if (leader != top) {
child = leader;
parent = child->real_parent;
leader = parent->group_leader;
goto up;
}
out:
read_unlock(&tasklist_lock);
}
#ifndef ARCH_MIN_MMSTRUCT_ALIGN
#define ARCH_MIN_MMSTRUCT_ALIGN 0
#endif
static void sighand_ctor(void *data)
{
struct sighand_struct *sighand = data;
spin_lock_init(&sighand->siglock);
init_waitqueue_head(&sighand->signalfd_wqh);
}
void __init proc_caches_init(void)
{
unsigned int mm_size;
sighand_cachep = kmem_cache_create("sighand_cache",
sizeof(struct sighand_struct), 0,
SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
SLAB_ACCOUNT, sighand_ctor);
signal_cachep = kmem_cache_create("signal_cache",
sizeof(struct signal_struct), 0,
SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
NULL);
files_cachep = kmem_cache_create("files_cache",
sizeof(struct files_struct), 0,
SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
NULL);
fs_cachep = kmem_cache_create("fs_cache",
sizeof(struct fs_struct), 0,
SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
NULL);
/*
* The mm_cpumask is located at the end of mm_struct, and is
* dynamically sized based on the maximum CPU number this system
* can have, taking hotplug into account (nr_cpu_ids).
*/
mm_size = sizeof(struct mm_struct) + cpumask_size();
mm_cachep = kmem_cache_create_usercopy("mm_struct",
mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
offsetof(struct mm_struct, saved_auxv),
sizeof_field(struct mm_struct, saved_auxv),
NULL);
vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
mmap_init();
nsproxy_cache_init();
}
/*
* Check constraints on flags passed to the unshare system call.
*/
static int check_unshare_flags(unsigned long unshare_flags)
{
if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP|
CLONE_NEWTIME))
return -EINVAL;
/*
* Not implemented, but pretend it works if there is nothing
* to unshare. Note that unsharing the address space or the
* signal handlers also need to unshare the signal queues (aka
* CLONE_THREAD).
*/
if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
if (!thread_group_empty(current))
return -EINVAL;
}
if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
if (refcount_read(&current->sighand->count) > 1)
return -EINVAL;
}
if (unshare_flags & CLONE_VM) {
if (!current_is_single_threaded())
return -EINVAL;
}
return 0;
}
/*
* Unshare the filesystem structure if it is being shared
*/
static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
{
struct fs_struct *fs = current->fs;
if (!(unshare_flags & CLONE_FS) || !fs)
return 0;
/* don't need lock here; in the worst case we'll do useless copy */
if (fs->users == 1)
return 0;
*new_fsp = copy_fs_struct(fs);
if (!*new_fsp)
return -ENOMEM;
return 0;
}
/*
* Unshare file descriptor table if it is being shared
*/
int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
struct files_struct **new_fdp)
{
struct files_struct *fd = current->files;
int error = 0;
if ((unshare_flags & CLONE_FILES) &&
(fd && atomic_read(&fd->count) > 1)) {
*new_fdp = dup_fd(fd, max_fds, &error);
if (!*new_fdp)
return error;
}
return 0;
}
/*
* unshare allows a process to 'unshare' part of the process
* context which was originally shared using clone. copy_*
* functions used by kernel_clone() 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.
*/
int ksys_unshare(unsigned long unshare_flags)
{
struct fs_struct *fs, *new_fs = NULL;
struct files_struct *fd, *new_fd = NULL;
struct cred *new_cred = NULL;
struct nsproxy *new_nsproxy = NULL;
int do_sysvsem = 0;
int err;
/*
* If unsharing a user namespace must also unshare the thread group
* and unshare the filesystem root and working directories.
*/
if (unshare_flags & CLONE_NEWUSER)
unshare_flags |= CLONE_THREAD | CLONE_FS;
/*
* If unsharing vm, must also unshare signal handlers.
*/
if (unshare_flags & CLONE_VM)
unshare_flags |= CLONE_SIGHAND;
/*
* If unsharing a signal handlers, must also unshare the signal queues.
*/
if (unshare_flags & CLONE_SIGHAND)
unshare_flags |= CLONE_THREAD;
/*
* If unsharing namespace, must also unshare filesystem information.
*/
if (unshare_flags & CLONE_NEWNS)
unshare_flags |= CLONE_FS;
err = check_unshare_flags(unshare_flags);
if (err)
goto bad_unshare_out;
/*
* 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))
do_sysvsem = 1;
err = unshare_fs(unshare_flags, &new_fs);
if (err)
goto bad_unshare_out;
err = unshare_fd(unshare_flags, NR_OPEN_MAX, &new_fd);
if (err)
goto bad_unshare_cleanup_fs;
err = unshare_userns(unshare_flags, &new_cred);
if (err)
goto bad_unshare_cleanup_fd;
err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
new_cred, new_fs);
if (err)
goto bad_unshare_cleanup_cred;
if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
if (do_sysvsem) {
/*
* CLONE_SYSVSEM is equivalent to sys_exit().
*/
exit_sem(current);
}
if (unshare_flags & CLONE_NEWIPC) {
/* Orphan segments in old ns (see sem above). */
exit_shm(current);
shm_init_task(current);
}
if (new_nsproxy)
switch_task_namespaces(current, new_nsproxy);
task_lock(current);
if (new_fs) {
fs = current->fs;
spin_lock(&fs->lock);
current->fs = new_fs;
if (--fs->users)
new_fs = NULL;
else
new_fs = fs;
spin_unlock(&fs->lock);
}
if (new_fd) {
fd = current->files;
current->files = new_fd;
new_fd = fd;
}
task_unlock(current);
if (new_cred) {
/* Install the new user namespace */
commit_creds(new_cred);
new_cred = NULL;
}
}
perf_event_namespaces(current);
bad_unshare_cleanup_cred:
if (new_cred)
put_cred(new_cred);
bad_unshare_cleanup_fd:
if (new_fd)
put_files_struct(new_fd);
bad_unshare_cleanup_fs:
if (new_fs)
free_fs_struct(new_fs);
bad_unshare_out:
return err;
}
SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
{
return ksys_unshare(unshare_flags);
}
/*
* 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(void)
{
struct task_struct *task = current;
struct files_struct *old, *copy = NULL;
int error;
error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, &copy);
if (error || !copy)
return error;
old = task->files;
task_lock(task);
task->files = copy;
task_unlock(task);
put_files_struct(old);
return 0;
}
int sysctl_max_threads(struct ctl_table *table, int write,
void *buffer, size_t *lenp, loff_t *ppos)
{
struct ctl_table t;
int ret;
int threads = max_threads;
int min = 1;
int max = MAX_THREADS;
t = *table;
t.data = &threads;
t.extra1 = &min;
t.extra2 = &max;
ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
if (ret || !write)
return ret;
max_threads = threads;
return 0;
}
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