linux-kernel - [PATCH] net: bridge: disable multicast while delete bridge

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Date:   Mon,  2 Nov 2020 22:38:28 +0800
From:   Menglong Dong <menglong8.dong@...il.com>
To:     roopa@...dia.com
Cc:     nikolay@...dia.com, davem@...emloft.net, kuba@...nel.org,
        bridge@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Menglong Dong <dong.menglong@....com.cn>
Subject: [PATCH] net: bridge: disable multicast while delete bridge

From: Menglong Dong <dong.menglong@....com.cn>

This commit seems make no sense, as bridge is destroyed when
br_multicast_dev_del is called.

In commit b1b9d366028f
("bridge: move bridge multicast cleanup to ndo_uninit"), Xin Long
fixed the use-after-free panic in br_multicast_group_expired by
moving br_multicast_dev_del to ndo_uninit. However, that patch is
not applied to 4.4.X, and the bug exists.

Fix that bug by disabling multicast in br_multicast_dev_del for
4.4.X, and there is no harm for other branches.

Signed-off-by: Menglong Dong <dong.menglong@....com.cn>
---
 net/bridge/br_multicast.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index eae898c3cff7..9992fdff2951 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -3369,6 +3369,7 @@ void br_multicast_dev_del(struct net_bridge *br)
 	hlist_for_each_entry_safe(mp, tmp, &br->mdb_list, mdb_node)
 		br_multicast_del_mdb_entry(mp);
 	hlist_move_list(&br->mcast_gc_list, &deleted_head);
+	br_opt_toggle(br, BROPT_MULTICAST_ENABLED, false);
 	spin_unlock_bh(&br->multicast_lock);
 
 	br_multicast_gc(&deleted_head);
-- 
2.25.1