diff options
| author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2016-01-15 16:57:31 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-01-15 17:56:32 -0800 |
| commit | 88f306b68cbb36e500da4b9601b2e3d13dd683c4 (patch) | |
| tree | e0373c2ee59446b3f8f9c2bfae9f75ff05e73f6c /fs | |
| parent | d645fc0eabbe783d34a14fbb31768ad8571f0ad4 (diff) | |
mm: fix locking order in mm_take_all_locks()
Dmitry Vyukov has reported[1] possible deadlock (triggered by his
syzkaller fuzzer):
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&hugetlbfs_i_mmap_rwsem_key);
lock(&mapping->i_mmap_rwsem);
lock(&hugetlbfs_i_mmap_rwsem_key);
lock(&mapping->i_mmap_rwsem);
Both traces points to mm_take_all_locks() as a source of the problem.
It doesn't take care about ordering or hugetlbfs_i_mmap_rwsem_key (aka
mapping->i_mmap_rwsem for hugetlb mapping) vs. i_mmap_rwsem.
huge_pmd_share() does memory allocation under hugetlbfs_i_mmap_rwsem_key
and allocator can take i_mmap_rwsem if it hit reclaim. So we need to
take i_mmap_rwsem from all hugetlb VMAs before taking i_mmap_rwsem from
rest of VMAs.
The patch also documents locking order for hugetlbfs_i_mmap_rwsem_key.
[1] http://lkml.kernel.org/r/CACT4Y+Zu95tBs-0EvdiAKzUOsb4tczRRfCRTpLr4bg_OP9HuVg@mail.gmail.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/hugetlbfs/inode.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 47789292a582..bbc333b01ca3 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -708,7 +708,7 @@ static struct inode *hugetlbfs_get_root(struct super_block *sb, /* * Hugetlbfs is not reclaimable; therefore its i_mmap_rwsem will never * be taken from reclaim -- unlike regular filesystems. This needs an - * annotation because huge_pmd_share() does an allocation under + * annotation because huge_pmd_share() does an allocation under hugetlb's * i_mmap_rwsem. */ static struct lock_class_key hugetlbfs_i_mmap_rwsem_key; |