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authorMichel Lespinasse <walken@google.com>2012-10-08 16:30:01 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-10-09 16:22:28 +0900
commitca42b26ab285edc5ee3f9faa48379d258db53c35 (patch)
tree4a9d68d4d730474dde75b1ffff106d7e3442aef1 /mm/mmap.c
parent227e4047488d3ee0173a914275a7fd207ad51e5b (diff)
mm: fix potential anon_vma locking issue in mprotect()
Fix an anon_vma locking issue in the following situation: - vma has no anon_vma - next has an anon_vma - vma is being shrunk / next is being expanded, due to an mprotect call We need to take next's anon_vma lock to avoid races with rmap users (such as page migration) while next is being expanded. Signed-off-by: Michel Lespinasse <walken@google.com> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> Acked-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mmap.c')
-rw-r--r--mm/mmap.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index 2ba27434e843..e3c365ff1b6a 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -573,8 +573,12 @@ again: remove_next = 1 + (end > next->vm_end);
*/
if (vma->anon_vma && (importer || start != vma->vm_start)) {
anon_vma = vma->anon_vma;
+ VM_BUG_ON(adjust_next && next->anon_vma &&
+ anon_vma != next->anon_vma);
+ } else if (adjust_next && next->anon_vma)
+ anon_vma = next->anon_vma;
+ if (anon_vma)
anon_vma_lock(anon_vma);
- }
if (root) {
flush_dcache_mmap_lock(mapping);