summaryrefslogtreecommitdiffstats
path: root/net
diff options
context:
space:
mode:
authorMel Gorman <mel@csn.ul.ie>2010-05-24 14:32:19 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-05-25 08:06:58 -0700
commit67b9509b2c68ae38cecb83a239881cb0ddf087dc (patch)
treea8cee4f4bec57ab44a993ce81df2a10a4980f0f8 /net
parent7f60c214fd3a360461f3286c6908084f7f8b1950 (diff)
downloadlinux-67b9509b2c68ae38cecb83a239881cb0ddf087dc.tar.gz
linux-67b9509b2c68ae38cecb83a239881cb0ddf087dc.tar.bz2
linux-67b9509b2c68ae38cecb83a239881cb0ddf087dc.zip
mm: migration: do not try to migrate unmapped anonymous pages
rmap_walk_anon() was triggering errors in memory compaction that look like use-after-free errors. The problem is that between the page being isolated from the LRU and rcu_read_lock() being taken, the mapcount of the page dropped to 0 and the anon_vma gets freed. This can happen during memory compaction if pages being migrated belong to a process that exits before migration completes. Hence, the use-after-free race looks like 1. Page isolated for migration 2. Process exits 3. page_mapcount(page) drops to zero so anon_vma was no longer reliable 4. unmap_and_move() takes the rcu_lock but the anon_vma is already garbage 4. call try_to_unmap, looks up tha anon_vma and "locks" it but the lock is garbage. This patch checks the mapcount after the rcu lock is taken. If the mapcount is zero, the anon_vma is assumed to be freed and no further action is taken. Signed-off-by: Mel Gorman <mel@csn.ul.ie> Acked-by: Rik van Riel <riel@redhat.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Christoph Lameter <cl@linux-foundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'net')
0 files changed, 0 insertions, 0 deletions