[PATCH] net: fix a potential rcu_read_lock() imbalance in rt6_fill_node()

[Eric Dumazet <eric.dumazet@gmail.com>]

Commit f2c31e32b378 (net: fix NULL dereferences in check_peer_redir() )
added a regression in rt6_fill_node(), leading to rcu_read_lock()
imbalance.

Thats because NLA_PUT() can make a jump to nla_put_failure label.

Fix this by using nla_put()

Many thanks to Ben Greear for his help

Reported-by: Ben Greear <greearb@candelatech.com>
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
 net/ipv6/route.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 24c456e..496b627 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2474,8 +2474,12 @@ static int rt6_fill_node(struct net *net,
 
 	rcu_read_lock();
 	n = dst_get_neighbour_noref(&rt->dst);
-	if (n)
-		NLA_PUT(skb, RTA_GATEWAY, 16, &n->primary_key);
+	if (n) {
+		if (nla_put(skb, RTA_GATEWAY, 16, &n->primary_key) < 0) {
+			rcu_read_unlock();
+			goto nla_put_failure;
+		}
+	}
 	rcu_read_unlock();
 
 	if (rt->dst.dev)