diff options
| author | Michel Machado <michel@digirati.com.br> | 2012-02-21 16:04:13 -0500 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2012-02-21 16:28:10 -0500 |
| commit | 84338a6c9dbb6ff3de4749864020f8f25d86fc81 (patch) | |
| tree | 100409d99686fa989c64d4f5aa12721a3fafa5d8 /net/core/neighbour.c | |
| parent | 3d8f93083be54696d3b7f8e8c6c70d411d01f9e8 (diff) | |
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/core/neighbour.c')
| -rw-r--r-- | net/core/neighbour.c | 2 |
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 |