[Bridge] [PATCH net] net: bridge: delete local fdbs on device init failure

Nikolay Aleksandrov nikolay at cumulusnetworks.com
Sun Jul 28 18:22:30 UTC 2019

On initialization failure we have to delete all local fdbs which were
inserted due to the default pvid. 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 fdbs 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 at syzkaller.appspotmail.com
Fixes: 5be5a2df40f0 ("bridge: Add filtering support for default_pvid")
Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
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)
+	/* delete auto-added default pvid local fdbs before flushing vlans
+	 * otherwise these will be leaked on bridge device init failure
+	 */
+	br_fdb_delete_by_port(br, NULL, 0, 1);
 	vg = br_vlan_group(br);
 	RCU_INIT_POINTER(br->vlgrp, NULL);

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