Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

1 files changed, 20 insertions, 9 deletions

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 57bf96d73e3b..5564eee1e980 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3763,16 +3763,27 @@ static int rtnl_fdb_dump(struct sk_buff *skb, struct netlink_callback *cb)
 	int err = 0;
 	int fidx = 0;
 
-	err = nlmsg_parse(cb->nlh, sizeof(struct ifinfomsg), tb,
-			  IFLA_MAX, ifla_policy, NULL);
-	if (err < 0) {
-		return -EINVAL;
-	} else if (err == 0) {
-		if (tb[IFLA_MASTER])
-			br_idx = nla_get_u32(tb[IFLA_MASTER]);
-	}
+	/* A hack to preserve kernel<->userspace interface.
+	 * Before Linux v4.12 this code accepted ndmsg since iproute2 v3.3.0.
+	 * However, ndmsg is shorter than ifinfomsg thus nlmsg_parse() bails.
+	 * So, check for ndmsg with an optional u32 attribute (not used here).
+	 * Fortunately these sizes don't conflict with the size of ifinfomsg
+	 * with an optional attribute.
+	 */
+	if (nlmsg_len(cb->nlh) != sizeof(struct ndmsg) &&
+	    (nlmsg_len(cb->nlh) != sizeof(struct ndmsg) +
+	     nla_attr_size(sizeof(u32)))) {
+		err = nlmsg_parse(cb->nlh, sizeof(struct ifinfomsg), tb,
+				  IFLA_MAX, ifla_policy, NULL);
+		if (err < 0) {
+			return -EINVAL;
+		} else if (err == 0) {
+			if (tb[IFLA_MASTER])
+				br_idx = nla_get_u32(tb[IFLA_MASTER]);
+		}
 
-	brport_idx = ifm->ifi_index;
+		brport_idx = ifm->ifi_index;
+	}
 
 	if (br_idx) {
 		br_dev = __dev_get_by_index(net, br_idx);