[ 051/143] neighbour: fix a race in neigh_destroy()

Willy Tarreau
2014-05-12T01:44:35Z

From: Eric Dumazet <eric.dumazet@gmail.com>

[ Upstream commit c9ab4d85de222f3390c67aedc9c18a50e767531e ]

There is a race in neighbour code, because neigh_destroy() uses
skb_queue_purge(&neigh->arp_queue) without holding neighbour lock,
while other parts of the code assume neighbour rwlock is what
protects arp_queue

Convert all skb_queue_purge() calls to the __skb_queue_purge() variant

Use __skb_queue_head_init() instead of skb_queue_head_init()
to make clear we do not use arp_queue.lock

And hold neigh->lock in neigh_destroy() to close the race.

Reported-by: Joe Jin <joe.jin@oracle.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
net/core/neighbour.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index e696250..fc9feaa 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -222,7 +222,7 @@ static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev)
we must kill timers etc. and move
it to safe state.
*/
- skb_queue_purge(&n->arp_queue);
+ __skb_queue_purge(&n->arp_queue);
n->output = neigh_blackhole;
if (n->nud_state & NUD_VALID)
n->nud_state = NUD_NOARP;
@@ -276,7 +276,7 @@ static struct neighbour *neigh_alloc(struct neigh_table *tbl)
if (!n)
goto out_entries;

- skb_queue_head_init(&n->arp_queue);
+ __skb_queue_head_init(&n->arp_queue);
rwlock_init(&n->lock);
n->updated = n->used = now;
n->nud_state = NUD_NONE;
@@ -646,7 +646,9 @@ void neigh_destroy(struct neighbour *neigh)
kfree(hh);
}

- skb_queue_purge(&neigh->arp_queue);
+ write_lock_bh(&neigh->lock);
+ __skb_queue_purge(&neigh->arp_queue);
+ write_unlock_bh(&neigh->lock);

dev_put(neigh->dev);
neigh_parms_put(neigh->parms);
@@ -789,7 +791,7 @@ static void neigh_invalidate(struct neighbour *neigh)
neigh->ops->error_report(neigh, skb);
write_lock(&neigh->lock);
}
- skb_queue_purge(&neigh->arp_queue);
+ __skb_queue_purge(&neigh->arp_queue);
}

/* Called when a timer expires for a neighbour entry. */
@@ -1105,7 +1107,7 @@ int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new,
n1->output(skb);
write_lock_bh(&neigh->lock);
}
- skb_queue_purge(&neigh->arp_queue);
+ __skb_queue_purge(&neigh->arp_queue);
}
out:
if (update_isrouter) {
--
1.7.12.2.21.g234cd45.dirty