neighbour: fix a race in neigh_destroy()

[ 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 7 insertions, 5 deletions

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 5c56b217b999..ce90b0264db5 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -231,7 +231,7 @@ 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->arp_queue_len_bytes = 0;
                                 n->output = neigh_blackhole;
                                 if (n->nud_state & NUD_VALID)
@@ -286,7 +286,7 @@ static struct neighbour *neigh_alloc(struct neigh_table *tbl, struct net_device
         if (!n)
                 goto out_entries;
 
-        skb_queue_head_init(&n->arp_queue);
+        __skb_queue_head_init(&n->arp_queue);
         rwlock_init(&n->lock);
         seqlock_init(&n->ha_lock);
         n->updated        = n->used = now;
@@ -708,7 +708,9 @@ void neigh_destroy(struct neighbour *neigh)
         if (neigh_del_timer(neigh))
                 pr_warn("Impossible event\n");
 
-        skb_queue_purge(&neigh->arp_queue);
+        write_lock_bh(&neigh->lock);
+        __skb_queue_purge(&neigh->arp_queue);
+        write_unlock_bh(&neigh->lock);
         neigh->arp_queue_len_bytes = 0;
 
         if (dev->netdev_ops->ndo_neigh_destroy)
@@ -858,7 +860,7 @@ 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);
         neigh->arp_queue_len_bytes = 0;
 }
 
@@ -1210,7 +1212,7 @@ int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new,
 
                         write_lock_bh(&neigh->lock);
                 }
-                skb_queue_purge(&neigh->arp_queue);
+                __skb_queue_purge(&neigh->arp_queue);
                 neigh->arp_queue_len_bytes = 0;
         }
 out: