diff options
| author | Michal Hocko <mhocko@suse.com> | 2017-08-18 15:16:12 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-08-18 15:32:01 -0700 |
| commit | 5b53a6ea886700a128b697a6fe8375340dea2c30 (patch) | |
| tree | b0b1fa8f6673367612dca66bce5c81d6bdbc7f11 | |
| parent | f6ba488073fe8159851fe398cc3c5ee383bb4c7a (diff) | |
mm: fix double mmap_sem unlock on MMF_UNSTABLE enforced SIGBUS
Tetsuo Handa has noticed that MMF_UNSTABLE SIGBUS path in
handle_mm_fault causes a lockdep splat
Out of memory: Kill process 1056 (a.out) score 603 or sacrifice child
Killed process 1056 (a.out) total-vm:4268108kB, anon-rss:2246048kB, file-rss:0kB, shmem-rss:0kB
a.out (1169) used greatest stack depth: 11664 bytes left
DEBUG_LOCKS_WARN_ON(depth <= 0)
------------[ cut here ]------------
WARNING: CPU: 6 PID: 1339 at kernel/locking/lockdep.c:3617 lock_release+0x172/0x1e0
CPU: 6 PID: 1339 Comm: a.out Not tainted 4.13.0-rc3-next-20170803+ #142
Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/02/2015
RIP: 0010:lock_release+0x172/0x1e0
Call Trace:
up_read+0x1a/0x40
__do_page_fault+0x28e/0x4c0
do_page_fault+0x30/0x80
page_fault+0x28/0x30
The reason is that the page fault path might have dropped the mmap_sem
and returned with VM_FAULT_RETRY. MMF_UNSTABLE check however rewrites
the error path to VM_FAULT_SIGBUS and we always expect mmap_sem taken in
that path. Fix this by taking mmap_sem when VM_FAULT_RETRY is held in
the MMF_UNSTABLE path.
We cannot simply add VM_FAULT_SIGBUS to the existing error code because
all arch specific page fault handlers and g-u-p would have to learn a
new error code combination.
Link: http://lkml.kernel.org/r/20170807113839.16695-2-mhocko@kernel.org
Fixes: 3f70dc38cec2 ("mm: make sure that kthreads will not refault oom reaped memory")
Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Andrea Argangeli <andrea@kernel.org>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Wenwei Tao <wenwei.tww@alibaba-inc.com>
Cc: <stable@vger.kernel.org> [4.9+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/memory.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/mm/memory.c b/mm/memory.c index e158f7ac6730..c717b5bcc80e 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3910,8 +3910,18 @@ int handle_mm_fault(struct vm_area_struct *vma, unsigned long address, * further. */ if (unlikely((current->flags & PF_KTHREAD) && !(ret & VM_FAULT_ERROR) - && test_bit(MMF_UNSTABLE, &vma->vm_mm->flags))) + && test_bit(MMF_UNSTABLE, &vma->vm_mm->flags))) { + + /* + * We are going to enforce SIGBUS but the PF path might have + * dropped the mmap_sem already so take it again so that + * we do not break expectations of all arch specific PF paths + * and g-u-p + */ + if (ret & VM_FAULT_RETRY) + down_read(&vma->vm_mm->mmap_sem); ret = VM_FAULT_SIGBUS; + } return ret; } |