From: Eric Dumazet <edumazet@google.com>
Date: Fri, 8 Jun 2012 06:25:00 +0000 (+0000)
Subject: l2tp: fix a race in l2tp_ip_sendmsg()
X-Git-Tag: v3.4.5~163
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=4ffa79bd261281152345b55d77da1709d1afdf3c;p=platform%2Fkernel%2Flinux-stable.git

l2tp: fix a race in l2tp_ip_sendmsg()

[ Upstream commit 4399a4df98a63e30fd16e9d0cecc46ea92269e8f ]

Commit 081b1b1bb27f (l2tp: fix l2tp_ip_sendmsg() route handling) added
a race, in case IP route cache is disabled.

In this case, we should not do the dst_release(&rt->dst), since it'll
free the dst immediately, instead of waiting a RCU grace period.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: James Chapman <jchapman@katalix.com>
Cc: Denys Fedoryshchenko <denys@visp.net.lb>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
index cc8ad7b..b1d4370 100644
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -516,10 +516,12 @@ static int l2tp_ip_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *m
 					   sk->sk_bound_dev_if);
 		if (IS_ERR(rt))
 			goto no_route;
-		if (connected)
+		if (connected) {
 			sk_setup_caps(sk, &rt->dst);
-		else
-			dst_release(&rt->dst); /* safe since we hold rcu_read_lock */
+		} else {
+			skb_dst_set(skb, &rt->dst);
+			goto xmit;
+		}
 	}
 
 	/* We dont need to clone dst here, it is guaranteed to not disappear.
@@ -527,6 +529,7 @@ static int l2tp_ip_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *m
 	 */
 	skb_dst_set_noref(skb, &rt->dst);
 
+xmit:
 	/* Queue the packet to IP for output */
 	rc = ip_queue_xmit(skb, &inet->cork.fl);
 	rcu_read_unlock();