[ 112/143] sctp: unbalanced rcu lock in ip_queue_xmit()

Willy Tarreau
2014-05-12T01:43:29Z

From: Nicolas Dichtel <nicolas.dichtel@6wind.com>

The bug was introduced in 2.6.32.61 by commit b8710128e201 ("inet: add RCU
protection to inet->opt") (it's a backport of upstream commit f6d8bd051c39).

In SCTP case, packet is already routed, hence we jump to the label
'packet_routed', but without rcu_read_lock(). After this label,
rcu_read_unlock() is called unconditionally.

Spotted-by: Guo Fengtian <fengtian.guo@6wind.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
net/ipv4/ip_output.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 7dde039..2cd69e3 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -320,13 +320,13 @@ int ip_queue_xmit(struct sk_buff *skb, int ipfragok)
/* Skip all of this if the packet is already routed,
* f.e. by something like SCTP.
*/
+ rcu_read_lock();
rt = skb_rtable(skb);
if (rt != NULL)
goto packet_routed;

/* Make sure we can route this packet. */
rt = (struct rtable *)__sk_dst_check(sk, 0);
- rcu_read_lock();
inet_opt = rcu_dereference(inet->inet_opt);
if (rt == NULL) {
__be32 daddr;
--
1.7.12.2.21.g234cd45.dirty