path: root/mm/mmap.c
diff options
authorKonstantin Khlebnikov <koct9i@gmail.com>2015-01-11 16:54:06 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2015-01-11 11:45:10 -0800
commitb800c91a0517071156e772d4fb329ad33590da62 (patch)
tree4b526ff1b00971161ee550e89f598bf12d159f80 /mm/mmap.c
parent690eac53daff34169a4d74fc7bfbd388c4896abb (diff)
mm: fix corner case in anon_vma endless growing prevention
Fix for BUG_ON(anon_vma->degree) splashes in unlink_anon_vmas() ("kernel BUG at mm/rmap.c:399!") caused by commit 7a3ef208e662 ("mm: prevent endless growth of anon_vma hierarchy") Anon_vma_clone() is usually called for a copy of source vma in destination argument. If source vma has anon_vma it should be already in dst->anon_vma. NULL in dst->anon_vma is used as a sign that it's called from anon_vma_fork(). In this case anon_vma_clone() finds anon_vma for reusing. Vma_adjust() calls it differently and this breaks anon_vma reusing logic: anon_vma_clone() links vma to old anon_vma and updates degree counters but vma_adjust() overrides vma->anon_vma right after that. As a result final unlink_anon_vmas() decrements degree for wrong anon_vma. This patch assigns ->anon_vma before calling anon_vma_clone(). Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com> Reported-and-tested-by: Chris Clayton <chris2553@googlemail.com> Reported-and-tested-by: Oded Gabbay <oded.gabbay@amd.com> Reported-and-tested-by: Chih-Wei Huang <cwhuang@android-x86.org> Acked-by: Rik van Riel <riel@redhat.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Daniel Forrest <dan.forrest@ssec.wisc.edu> Cc: Michal Hocko <mhocko@suse.cz> Cc: stable@vger.kernel.org # to match back-porting of 7a3ef208e662 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mmap.c')
1 files changed, 4 insertions, 2 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index 0bb74ca2139..7f684d5a808 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -778,10 +778,12 @@ again: remove_next = 1 + (end > next->vm_end);
if (exporter && exporter->anon_vma && !importer->anon_vma) {
int error;
+ importer->anon_vma = exporter->anon_vma;
error = anon_vma_clone(importer, exporter);
- if (error)
+ if (error) {
+ importer->anon_vma = NULL;
return error;
- importer->anon_vma = exporter->anon_vma;
+ }