[PATCH 4.9 10/32] vxlan: fix oops in dev_fill_metadata_dst

[Greg Kroah-Hartman]

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

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

From: Paolo Abeni <pabeni@xxxxxxxxxx>


[ Upstream commit 22f0708a718daea5e79de2d29b4829de016a4ff4 ]

Since the commit 0c1d70af924b ("net: use dst_cache for vxlan device")
vxlan_fill_metadata_dst() calls vxlan_get_route() passing a NULL
dst_cache pointer, so the latter should explicitly check for
valid dst_cache ptr. Unfortunately the commit d71785ffc7e7 ("net: add
dst_cache to ovs vxlan lwtunnel") removed said check.

As a result is possible to trigger a null pointer access calling
vxlan_fill_metadata_dst(), e.g. with:

ovs-vsctl add-br ovs-br0
ovs-vsctl add-port ovs-br0 vxlan0 -- set interface vxlan0 \
	type=vxlan options:remote_ip=192.168.1.1 \
	options:key=1234 options:dst_port=4789 ofport_request=10
ip address add dev ovs-br0 172.16.1.2/24
ovs-vsctl set Bridge ovs-br0 ipfix=@i -- --id=@i create IPFIX \
	targets=\"172.16.1.1:1234\" sampling=1
iperf -c 172.16.1.1 -u -l 1000 -b 10M -t 1 -p 1234

This commit addresses the issue passing to vxlan_get_route() the
dst_cache already available into the lwt info processed by
vxlan_fill_metadata_dst().

Fixes: d71785ffc7e7 ("net: add dst_cache to ovs vxlan lwtunnel")
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Acked-by: Jiri Benc <jbenc@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/vxlan.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -2449,7 +2449,8 @@ static int vxlan_fill_metadata_dst(struc
 			return -EINVAL;
 		rt = vxlan_get_route(vxlan, skb, 0, info->key.tos,
 				     info->key.u.ipv4.dst,
-				     &info->key.u.ipv4.src, NULL, info);
+				     &info->key.u.ipv4.src,
+				     &info->dst_cache, info);
 		if (IS_ERR(rt))
 			return PTR_ERR(rt);
 		ip_rt_put(rt);
@@ -2459,7 +2460,8 @@ static int vxlan_fill_metadata_dst(struc
 
 		ndst = vxlan6_get_route(vxlan, skb, 0, info->key.tos,
 					info->key.label, &info->key.u.ipv6.dst,
-					&info->key.u.ipv6.src, NULL, info);
+					&info->key.u.ipv6.src,
+					&info->dst_cache, info);
 		if (IS_ERR(ndst))
 			return PTR_ERR(ndst);
 		dst_release(ndst);