From 0062d19dc7de879c3c1033f6ea970a6f8e8e8a1f Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Sun, 15 Mar 2015 21:12:04 +1100 Subject: [PATCH] rhashtable: Fix use-after-free in rhashtable_walk_stop The commit 62cd523211c1e03eb4ce7e0618396a526602cbac ("rhashtable: Move future_tbl into struct bucket_table") introduced a use-after- free bug in rhashtable_walk_stop because it dereferences tbl after droping the RCU read lock. This patch fixes it by moving the RCU read unlock down to the bottom of rhashtable_walk_stop. In fact this was how I had it originally but it got dropped while rearranging patches because this one depended on the async freeing of bucket_table. Signed-off-by: Herbert Xu Signed-off-by: David S. Miller --- lib/rhashtable.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/lib/rhashtable.c b/lib/rhashtable.c index 9d53a46dcca9c..b916679b3e3b7 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -854,10 +854,8 @@ void rhashtable_walk_stop(struct rhashtable_iter *iter) struct rhashtable *ht; struct bucket_table *tbl = iter->walker->tbl; - rcu_read_unlock(); - if (!tbl) - return; + goto out; ht = iter->ht; @@ -869,6 +867,9 @@ void rhashtable_walk_stop(struct rhashtable_iter *iter) mutex_unlock(&ht->mutex); iter->p = NULL; + +out: + rcu_read_unlock(); } EXPORT_SYMBOL_GPL(rhashtable_walk_stop); -- 2.39.5