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authorMichel Machado <michel@digirati.com.br>2012-02-21 16:04:13 -0500
committerDavid S. Miller <davem@davemloft.net>2012-02-21 16:28:10 -0500
commit84338a6c9dbb6ff3de4749864020f8f25d86fc81 (patch)
tree100409d99686fa989c64d4f5aa12721a3fafa5d8 /net
parent3d8f93083be54696d3b7f8e8c6c70d411d01f9e8 (diff)
downloadlinux-linaro-stable-84338a6c9dbb6ff3de4749864020f8f25d86fc81.tar.gz
neighbour: Fixed race condition at tbl->nht
When the fixed race condition happens: 1. While function neigh_periodic_work scans the neighbor hash table pointed by field tbl->nht, it unlocks and locks tbl->lock between buckets in order to call cond_resched. 2. Assume that function neigh_periodic_work calls cond_resched, that is, the lock tbl->lock is available, and function neigh_hash_grow runs. 3. Once function neigh_hash_grow finishes, and RCU calls neigh_hash_free_rcu, the original struct neigh_hash_table that function neigh_periodic_work was using doesn't exist anymore. 4. Once back at neigh_periodic_work, whenever the old struct neigh_hash_table is accessed, things can go badly. Signed-off-by: Michel Machado <michel@digirati.com.br> Acked-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/core/neighbour.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index e287346e0934..2a83914b0277 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -826,6 +826,8 @@ next_elt:
write_unlock_bh(&tbl->lock);
cond_resched();
write_lock_bh(&tbl->lock);
+ nht = rcu_dereference_protected(tbl->nht,
+ lockdep_is_held(&tbl->lock));
}
/* Cycle through all hash buckets every base_reachable_time/2 ticks.
* ARP entry timeouts range from 1/2 base_reachable_time to 3/2