Commit 84338a6c authored by Michel Machado's avatar Michel Machado Committed by David S. Miller

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: default avatarMichel Machado <michel@digirati.com.br>
Acked-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3d8f9308
...@@ -826,6 +826,8 @@ static void neigh_periodic_work(struct work_struct *work) ...@@ -826,6 +826,8 @@ static void neigh_periodic_work(struct work_struct *work)
write_unlock_bh(&tbl->lock); write_unlock_bh(&tbl->lock);
cond_resched(); cond_resched();
write_lock_bh(&tbl->lock); 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. /* Cycle through all hash buckets every base_reachable_time/2 ticks.
* ARP entry timeouts range from 1/2 base_reachable_time to 3/2 * ARP entry timeouts range from 1/2 base_reachable_time to 3/2
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment