netdev - [PATCH net v2] net: bridge: delete local fdb on device init failure

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Message-Id: <20190729092841.4260-1-nikolay@cumulusnetworks.com>
Date:   Mon, 29 Jul 2019 12:28:41 +0300
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, roopa@...ulusnetworks.com,
        bridge@...ts.linux-foundation.org,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
        syzbot+88533dc8b582309bf3ee@...kaller.appspotmail.com
Subject: [PATCH net v2] net: bridge: delete local fdb on device init failure

On initialization failure we have to delete the local fdb which was
inserted due to the default pvid creation. This problem has been present
since the inception of default_pvid. Note that currently there are 2 cases:
1) in br_dev_init() when br_multicast_init() fails
2) if register_netdevice() fails after calling ndo_init()

This patch takes care of both since br_vlan_flush() is called on both
occasions. Also the new fdb delete would be a no-op on normal bridge
device destruction since the local fdb would've been already flushed by
br_dev_delete(). This is not an issue for ports since nbp_vlan_init() is
called last when adding a port thus nothing can fail after it.

Reported-by: syzbot+88533dc8b582309bf3ee@...kaller.appspotmail.com
Fixes: 5be5a2df40f0 ("bridge: Add filtering support for default_pvid")
Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
---
v2: reworded the commit message and comment so they're not plural, we're
    talking about a single bridge local fdb added on the init vlan creation
    of the default pvid

Tested with the provided reproducer and can no longer trigger the leak.
Also tested the br_multicast_init() failure manually by making it always
return an error.

 net/bridge/br_vlan.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 021cc9f66804..3e6a702e4c21 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c
@@ -715,6 +715,11 @@ void br_vlan_flush(struct net_bridge *br)

 	ASSERT_RTNL();

+	/* delete auto-added default pvid local fdb before flushing vlans
+	 * otherwise it will be leaked on bridge device init failure
+	 */
+	br_fdb_delete_by_port(br, NULL, 0, 1);
+
 	vg = br_vlan_group(br);
 	__vlan_flush(vg);
 	RCU_INIT_POINTER(br->vlgrp, NULL);
-- 
2.21.0