[PATCH net] net: openvswitch: fix nested key length validation in the set() action

[Ilya Maximets]

It's not safe to access nla_len(ovs_key) if the data is smaller than
the netlink header.  Check that the attribute is OK first.

Fixes: ccb1352e76cf ("net: Add Open vSwitch kernel components.")
Reported-by: syzbot+b07a9da40df1576b8048@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=b07a9da40df1576b8048
Tested-by: syzbot+b07a9da40df1576b8048@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ilya Maximets <i.maximets@xxxxxxx>
---
 net/openvswitch/flow_netlink.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c
index 95e0dd14dc1a..518be23e48ea 100644
--- a/net/openvswitch/flow_netlink.c
+++ b/net/openvswitch/flow_netlink.c
@@ -2876,7 +2876,8 @@ static int validate_set(const struct nlattr *a,
 	size_t key_len;
 
 	/* There can be only one key in a action */
-	if (nla_total_size(nla_len(ovs_key)) != nla_len(a))
+	if (!nla_ok(ovs_key, nla_len(a)) ||
+	    nla_total_size(nla_len(ovs_key)) != nla_len(a))
 		return -EINVAL;
 
 	key_len = nla_len(ovs_key);
-- 
2.49.0