rmap_walk_anon() does not use page_lock_anon_vma() for looking up and locking an anon_vma. One important difference between page_lock_anon_vma() and rmap_walk_anon() is that the page_lock_anon_vma() takes the RCU lock before the lookup so that the anon_vma does not disappear. There does not appear to be locking in place that prevents the anon_vma disappearing before the spinlock is taken. This patch puts a rcu_read_lock() around the anon_vma lookup similar to what page_lock_anon_vma() does to prevent an accidental use-after-free. Signed-off-by: Mel Gorman <mel@xxxxxxxxx> --- mm/rmap.c | 7 ++++++- 1 files changed, 6 insertions(+), 1 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index b468d5f..fb695d3 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1233,9 +1233,10 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *, * This needs to be reviewed later: avoiding page_lock_anon_vma() * is risky, and currently limits the usefulness of rmap_walk(). */ + rcu_read_lock(); anon_vma = page_anon_vma(page); if (!anon_vma) - return ret; + goto out_rcu_unlock; spin_lock(&anon_vma->lock); /* @@ -1256,6 +1257,10 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *, out_anon_unlock: spin_unlock(&anon_vma->lock); + +out_rcu_unlock: + rcu_read_unlock(); + return ret; } -- 1.6.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>