The patch titled
Subject: shmem: pin the file in shmem_fault() if mmap_sem is dropped
has been added to the -mm tree. Its filename is
shmem-pin-the-file-in-shmem_fault-if-mmap_sem-is-dropped.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/shmem-pin-the-file-in-shmem_fault-if-mmap_sem-is-dropped.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/shmem-pin-the-file-in-shmem_fault-if-mmap_sem-is-dropped.patch
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------------------------------------------------------
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: shmem: pin the file in shmem_fault() if mmap_sem is dropped
syzbot found the following crash:
BUG: KASAN: use-after-free in perf_trace_lock_acquire+0x401/0x530
include/trace/events/lock.h:13
Read of size 8 at addr ffff8880a5cf2c50 by task syz-executor.0/26173
CPU: 0 PID: 26173 Comm: syz-executor.0 Not tainted 5.3.0-rc6 #146
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
print_address_description.cold+0xd4/0x306 mm/kasan/report.c:351
__kasan_report.cold+0x1b/0x36 mm/kasan/report.c:482
kasan_report+0x12/0x17 mm/kasan/common.c:618
__asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
perf_trace_lock_acquire+0x401/0x530 include/trace/events/lock.h:13
trace_lock_acquire include/trace/events/lock.h:13 [inline]
lock_acquire+0x2de/0x410 kernel/locking/lockdep.c:4411
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:338 [inline]
shmem_fault+0x5ec/0x7b0 mm/shmem.c:2034
__do_fault+0x111/0x540 mm/memory.c:3083
do_shared_fault mm/memory.c:3535 [inline]
do_fault mm/memory.c:3613 [inline]
handle_pte_fault mm/memory.c:3840 [inline]
__handle_mm_fault+0x2adf/0x3f20 mm/memory.c:3964
handle_mm_fault+0x1b5/0x6b0 mm/memory.c:4001
do_user_addr_fault arch/x86/mm/fault.c:1441 [inline]
__do_page_fault+0x536/0xdd0 arch/x86/mm/fault.c:1506
do_page_fault+0x38/0x590 arch/x86/mm/fault.c:1530
page_fault+0x39/0x40 arch/x86/entry/entry_64.S:1202
It happens if the VMA got unmapped under us while we dropped mmap_sem
and inode got freed.
Pinning the file if we drop mmap_sem fixes the issue.
Link: http://lkml.kernel.org/r/20190927083908.rhifa4mmaxefc24r@box
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reported-by: syzbot+03ee87124ee05af991bd@xxxxxxxxxxxxxxxxxxxxxxxxx
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Josef Bacik <josef@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
--- a/mm/shmem.c~shmem-pin-the-file-in-shmem_fault-if-mmap_sem-is-dropped
+++ a/mm/shmem.c
@@ -2022,16 +2022,14 @@ static vm_fault_t shmem_fault(struct vm_
shmem_falloc->waitq &&
vmf->pgoff >= shmem_falloc->start &&
vmf->pgoff < shmem_falloc->next) {
+ struct file *fpin;
wait_queue_head_t *shmem_falloc_waitq;
DEFINE_WAIT_FUNC(shmem_fault_wait, synchronous_wake_function);
ret = VM_FAULT_NOPAGE;
- if ((vmf->flags & FAULT_FLAG_ALLOW_RETRY) &&
- !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
- /* It's polite to up mmap_sem if we can */
- up_read(&vma->vm_mm->mmap_sem);
+ fpin = maybe_unlock_mmap_for_io(vmf, NULL);
+ if (fpin)
ret = VM_FAULT_RETRY;
- }
shmem_falloc_waitq = shmem_falloc->waitq;
prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
@@ -2049,6 +2047,9 @@ static vm_fault_t shmem_fault(struct vm_
spin_lock(&inode->i_lock);
finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
spin_unlock(&inode->i_lock);
+
+ if (fpin)
+ fput(fpin);
return ret;
}
spin_unlock(&inode->i_lock);
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
shmem-pin-the-file-in-shmem_fault-if-mmap_sem-is-dropped.patch
