diff options
| author | Andrea Arcangeli <aarcange@redhat.com> | 2017-02-22 15:43:52 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-02-22 16:41:29 -0800 |
| commit | a425d3584e7e69587aa441e91c7ffce7f47004d7 (patch) | |
| tree | 521ff37f093bd1bc9fc280fac65f21de0bd155b1 /mm/shmem.c | |
| parent | 9cc90c664a65f9b6b9f3ce1c719f1308539427bd (diff) | |
userfaultfd: shmem: avoid a lockup resulting from corrupted page->flags
Use the non atomic version of __SetPageUptodate while the page is still
private and not visible to lookup operations. Using the non atomic
version after the page is already visible to lookups is unsafe as there
would be concurrent lock_page operation modifying the page->flags while
it runs.
This solves a lockup in find_lock_entry with the userfaultfd_shmem
selftest.
userfaultfd_shm D14296 691 1 0x00000004
Call Trace:
schedule+0x3d/0x90
schedule_timeout+0x228/0x420
io_schedule_timeout+0xa4/0x110
__lock_page+0x12d/0x170
find_lock_entry+0xa4/0x190
shmem_getpage_gfp+0xb9/0xc30
shmem_fault+0x70/0x1c0
__do_fault+0x21/0x150
handle_mm_fault+0xec9/0x1490
__do_page_fault+0x20d/0x520
trace_do_page_fault+0x61/0x270
do_async_page_fault+0x19/0x80
async_page_fault+0x25/0x30
Link: http://lkml.kernel.org/r/20170116180408.12184-2-aarcange@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reported-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/shmem.c')
| -rw-r--r-- | mm/shmem.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/mm/shmem.c b/mm/shmem.c index 4e5e7a57e5b4..8d7d80cf8708 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2248,6 +2248,7 @@ int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm, VM_BUG_ON(PageLocked(page) || PageSwapBacked(page)); __SetPageLocked(page); __SetPageSwapBacked(page); + __SetPageUptodate(page); ret = mem_cgroup_try_charge(page, dst_mm, gfp, &memcg, false); if (ret) @@ -2272,8 +2273,6 @@ int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm, if (!pte_none(*dst_pte)) goto out_release_uncharge_unlock; - __SetPageUptodate(page); - lru_cache_add_anon(page); spin_lock(&info->lock); |