Specifying ifindex in a RTM_GETVLAN dump leads to an infinite repetition
of the same entries. netlink_dump() normally calls the dump function
repeatedly until it returns 0 which br_vlan_rtm_dump() never does in
that case.

Fixes: 8dcea187088b ("net: bridge: vlan: add rtm definitions and dump support")
Signed-off-by: Benjamin Poirier <redacted>
---
 net/bridge/br_vlan.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

The problem can be reproduced by using the following iproute2 patch and
running:
ip link add br0 type bridge
ip link add dummy0 master br0 type dummy
bridge vlan add dev dummy0 vid 100

./bridge/bridge -d vlan show dev dummy0
[infinite loop]

	diff --git a/bridge/vlan.c b/bridge/vlan.c
	index 8300f353..f206a671 100644
	--- a/bridge/vlan.c
	+++ b/bridge/vlan.c
	@@ -1128,7 +1128,8 @@ static int vlan_show(int argc, char **argv, int subject)
		if (show_details && subject == VLAN_SHOW_VLAN) {
			__u32 dump_flags = show_stats ? BRIDGE_VLANDB_DUMPF_STATS : 0;
	 
	-		if (rtnl_brvlandump_req(&rth, PF_BRIDGE, dump_flags) < 0) {
	+		if (rtnl_brvlandump_req(&rth, PF_BRIDGE, dump_flags,
	+					filter_index) < 0) {
				perror("Cannot send dump request");
				exit(1);
			}
	@@ -1240,7 +1241,8 @@ static int vlan_global_show(int argc, char **argv)
	 
		new_json_obj(json);
	 
	-	if (rtnl_brvlandump_req(&rth, PF_BRIDGE, dump_flags) < 0) {
	+	if (rtnl_brvlandump_req(&rth, PF_BRIDGE, dump_flags, filter_index)
	+	    < 0) {
			perror("Cannot send dump request");
			exit(1);
		}
	diff --git a/include/libnetlink.h b/include/libnetlink.h
	index 9e4cc101..276b7fbf 100644
	--- a/include/libnetlink.h
	+++ b/include/libnetlink.h
	@@ -69,7 +69,8 @@ int rtnl_neightbldump_req(struct rtnl_handle *rth, int family)
		__attribute__((warn_unused_result));
	 int rtnl_mdbdump_req(struct rtnl_handle *rth, int family)
		__attribute__((warn_unused_result));
	-int rtnl_brvlandump_req(struct rtnl_handle *rth, int family, __u32 dump_flags)
	+int rtnl_brvlandump_req(struct rtnl_handle *rth, int family, __u32 dump_flags,
	+			int ifindex)
		__attribute__((warn_unused_result));
	 int rtnl_netconfdump_req(struct rtnl_handle *rth, int family)
		__attribute__((warn_unused_result));
	diff --git a/lib/libnetlink.c b/lib/libnetlink.c
	index 7e977a67..e0fce8e5 100644
	--- a/lib/libnetlink.c
	+++ b/lib/libnetlink.c
	@@ -450,7 +450,8 @@ int rtnl_mdbdump_req(struct rtnl_handle *rth, int family)
		return send(rth->fd, &req, sizeof(req), 0);
	 }
	 
	-int rtnl_brvlandump_req(struct rtnl_handle *rth, int family, __u32 dump_flags)
	+int rtnl_brvlandump_req(struct rtnl_handle *rth, int family, __u32 dump_flags,
	+			int ifindex)
	 {
		struct {
			struct nlmsghdr nlh;
	@@ -462,6 +463,7 @@ int rtnl_brvlandump_req(struct rtnl_handle *rth, int family, __u32 dump_flags)
			.nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
			.nlh.nlmsg_seq = rth->dump = ++rth->seq,
			.bvm.family = family,
	+		.bvm.ifindex = ifindex,
		};
	 
		addattr32(&req.nlh, sizeof(req), BRIDGE_VLANDB_DUMP_FLAGS, dump_flags);
	-- 

diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 84ba456a78cc..2e606f2b9a4d 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c

@@ -2013,7 +2013,7 @@ static int br_vlan_rtm_dump(struct sk_buff *skb, struct netlink_callback *cb)
 		dump_flags = nla_get_u32(dtb[BRIDGE_VLANDB_DUMP_FLAGS]);
 
 	rcu_read_lock();
-	if (bvm->ifindex) {
+	if (bvm->ifindex && !s_idx) {
 		dev = dev_get_by_index_rcu(net, bvm->ifindex);
 		if (!dev) {
 			err = -ENODEV;

@@ -2022,7 +2022,9 @@ static int br_vlan_rtm_dump(struct sk_buff *skb, struct netlink_callback *cb)
 		err = br_vlan_dump_dev(dev, skb, cb, dump_flags);
 		if (err && err != -EMSGSIZE)
 			goto out_err;
-	} else {
+		else if (!err)
+			idx++;
+	} else if (!bvm->ifindex) {
 		for_each_netdev_rcu(net, dev) {
 			if (idx < s_idx)
 				goto skip;

-- 
2.34.1