netlink: validate addr_len on bind

Otherwise an out of bounds read could happen.

Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 9ee52b6..c0353d5 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -669,6 +669,9 @@
 	struct sockaddr_nl *nladdr = (struct sockaddr_nl *)addr;
 	int err;
 
+	if (addr_len < sizeof(struct sockaddr_nl))
+		return -EINVAL;
+
 	if (nladdr->nl_family != AF_NETLINK)
 		return -EINVAL;