diff options
| author | Michel Machado <michel@digirati.com.br> | 2012-02-21 11:04:13 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-03-19 09:02:21 -0700 |
| commit | 983af6e10958557843e4b5546c96e371ee3c8ddd (patch) | |
| tree | f7cad5124d188da418f139c6d9795f8b93d8b69f /net/core | |
| parent | d94202bc7eb5fbbe464d8bb7a7dd26b3d385faa2 (diff) | |
neighbour: Fixed race condition at tbl->nht
[ Upstream commit 84338a6c9dbb6ff3de4749864020f8f25d86fc81 ]
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>
CC: "David S. Miller" <davem@davemloft.net>
CC: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net/core')
| -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 5ac07d31fbc..7aafaeddfcb 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -802,6 +802,8 @@ 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 |