From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Thu, 23 Sep 2010 21:46:03 +0000 (+0000)
Subject: net: fix rcu use in ip_route_output_slow
X-Git-Tag: v2.6.37-rc1~147^2~352
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=83180af0b0ea166adf8249f4513beb7355f9b4c9;p=pandora-kernel.git

net: fix rcu use in ip_route_output_slow

__in_dev_get_rtnl(dev_out) is called while RTNL is not held, thus
triggers a lockdep fault.

At this point, we only perform a raw test of dev_out->ip_ptr being NULL,
we dont need to make sure ip_ptr cant changed right after.

We can use rcu_dereference_raw() for this.

Reported-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index ae1d4a41f1c6..98beda47bc99 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2579,7 +2579,7 @@ static int ip_route_output_slow(struct net *net, struct rtable **rp,
 			goto out;
 
 		/* RACE: Check return value of inet_select_addr instead. */
-		if (__in_dev_get_rtnl(dev_out) == NULL) {
+		if (rcu_dereference_raw(dev_out->ip_ptr) == NULL) {
 			dev_put(dev_out);
 			goto out;	/* Wrong error code */
 		}