linux-kernel - [ 167/175] net: fix a potential rcu_read_lock() imbalance in rt6_fill

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Message-Id: <20120330194859.751295658@linuxfoundation.org>
Date:	Fri, 30 Mar 2012 12:51:12 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Ben Greear <greearb@...delatech.com>,
	Dave Jones <davej@...hat.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [ 167/175] net: fix a potential rcu_read_lock() imbalance in rt6_fill_node()

3.3-stable review patch.  If anyone has any objections, please let me know.

------------------


From: Eric Dumazet <eric.dumazet@...il.com>

[ Upstream commit 94f826b8076e2cb92242061e92f21b5baa3eccc2 ]

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@...delatech.com>
Reported-by: Dave Jones <davej@...hat.com>
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
Tested-by: Ben Greear <greearb@...delatech.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv6/route.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2461,8 +2461,12 @@ 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)


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