Re: [PATCH net] net: bridge: vlan: Fix dumping with ifindex

On 25/01/2022 10:24, Nikolay Aleksandrov wrote:

On 25/01/2022 08:19, Benjamin Poirier wrote:

quoted

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(-)

[snip]

quoted

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;

Acked-by: Nikolay Aleksandrov <redacted>

Actually I'd prefer an alternative that would encapsulate handling the single
device dump in its block, avoid all the "else if"s and is simpler (untested):

diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 84ba456a78cc..43201260e37b 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c

@@ -2020,7 +2020,8 @@ static int br_vlan_rtm_dump(struct sk_buff *skb, struct netlink_callback *cb)
                        goto out_err;
                }
                err = br_vlan_dump_dev(dev, skb, cb, dump_flags);
-               if (err && err != -EMSGSIZE)
+               /* if the dump completed without an error we return 0 here */
+               if (err != -EMSGSIZE)
                        goto out_err;
        } else {
                for_each_netdev_rcu(net, dev) {