[PATCH] net: fix lockdep issue in __neigh_event_send

["Maciej Żenczykowski" <zenczykowski@gmail.com>]

From: Maciej Żenczykowski <maze@google.com>

skb's should be freed once neigh->lock is no longer held.

Google-Bug-Id: 4561441
Signed-off-by: Maciej Żenczykowski <maze@google.com>
CC: MuraliRaja Muniraju <muralira@google.com>
---
 net/core/neighbour.c |   12 ++++++------
 1 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 4002261..53d034a 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -949,6 +949,7 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
 {
 	int rc;
 	bool immediate_probe = false;
+	struct sk_buff *buff_to_free = NULL;
 
 	write_lock_bh(&neigh->lock);
 
@@ -969,10 +970,10 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
 		} else {
 			neigh->nud_state = NUD_FAILED;
 			neigh->updated = jiffies;
-			write_unlock_bh(&neigh->lock);
 
-			kfree_skb(skb);
-			return 1;
+			buff_to_free = skb;
+			rc = 1;
+			goto out_unlock_bh;
 		}
 	} else if (neigh->nud_state & NUD_STALE) {
 		NEIGH_PRINTK2("neigh %p is delayed.\n", neigh);
@@ -986,9 +987,7 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
 		if (skb) {
 			if (skb_queue_len(&neigh->arp_queue) >=
 			    neigh->parms->queue_len) {
-				struct sk_buff *buff;
-				buff = __skb_dequeue(&neigh->arp_queue);
-				kfree_skb(buff);
+				buff_to_free = __skb_dequeue(&neigh->arp_queue);
 				NEIGH_CACHE_STAT_INC(neigh->tbl, unres_discards);
 			}
 			skb_dst_force(skb);
@@ -1002,6 +1001,7 @@ out_unlock_bh:
 	else
 		write_unlock(&neigh->lock);
 	local_bh_enable();
+	kfree_skb(buff_to_free);
 	return rc;
 }
 EXPORT_SYMBOL(__neigh_event_send);
-- 
1.7.3.1