[PATCH 3.13.y-ckt 03/96] ipv4: fix nexthop attlen check in fib_nh_match

[Kamal Mostafa]

3.13.11-ckt13 -stable review patch.  If anyone has any objections, please let me know.

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

From: Jiri Pirko <jiri at resnulli.us>

[ Upstream commit f76936d07c4eeb36d8dbb64ebd30ab46ff85d9f7 ]

fib_nh_match does not match nexthops correctly. Example:

ip route add 172.16.10/24 nexthop via 192.168.122.12 dev eth0 \
                          nexthop via 192.168.122.13 dev eth0
ip route del 172.16.10/24 nexthop via 192.168.122.14 dev eth0 \
                          nexthop via 192.168.122.15 dev eth0

Del command is successful and route is removed. After this patch
applied, the route is correctly matched and result is:
RTNETLINK answers: No such process

Please consider this for stable trees as well.

Fixes: 4e902c57417c4 ("[IPv4]: FIB configuration using struct fib_config")
Signed-off-by: Jiri Pirko <jiri at resnulli.us>
Acked-by: Eric Dumazet <edumazet at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/ipv4/fib_semantics.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 8fccc50..1fd7cb2 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -534,7 +534,7 @@ int fib_nh_match(struct fib_config *cfg, struct fib_info *fi)
 			return 1;
 
 		attrlen = rtnh_attrlen(rtnh);
-		if (attrlen < 0) {
+		if (attrlen > 0) {
 			struct nlattr *nla, *attrs = rtnh_attrs(rtnh);
 
 			nla = nla_find(attrs, attrlen, RTA_GATEWAY);
-- 
1.9.1