linux-kernel - [PATCH 5.10 092/100] net: bridge: vlan: fix single net device option dumping

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Date:   Mon, 31 Jan 2022 11:56:53 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Benjamin Poirier <bpoirier@...dia.com>,
        Nikolay Aleksandrov <nikolay@...dia.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 092/100] net: bridge: vlan: fix single net device option dumping

From: Nikolay Aleksandrov <nikolay@...dia.com>

[ Upstream commit dcb2c5c6ca9b9177f04abaf76e5a983d177c9414 ]

When dumping vlan options for a single net device we send the same
entries infinitely because user-space expects a 0 return at the end but
we keep returning skb->len and restarting the dump on retry. Fix it by
returning the value from br_vlan_dump_dev() if it completed or there was
an error. The only case that must return skb->len is when the dump was
incomplete and needs to continue (-EMSGSIZE).

Reported-by: Benjamin Poirier <bpoirier@...dia.com>
Fixes: 8dcea187088b ("net: bridge: vlan: add rtm definitions and dump support")
Signed-off-by: Nikolay Aleksandrov <nikolay@...dia.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/bridge/br_vlan.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 08c77418c687b..1f508d998fb2d 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c
@@ -1873,7 +1873,8 @@ 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) {
-- 
2.34.1