netdev - [PATCH net 2/2] net: dsa: Avoid cross-chip syncing of VLAN filtering

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Date:   Mon, 24 Jan 2022 22:09:44 +0100
From:   Tobias Waldekranz <tobias@...dekranz.com>
To:     davem@...emloft.net, kuba@...nel.org
Cc:     netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH net 2/2] net: dsa: Avoid cross-chip syncing of VLAN filtering

Changes to VLAN filtering are not applicable to cross-chip
notifications.

On a system like this:

.-----.   .-----.   .-----.
| sw1 +---+ sw2 +---+ sw3 |
'-1-2-'   '-1-2-'   '-1-2-'

Before this change, upon sw1p1 leaving a bridge, a call to
dsa_port_vlan_filtering would also be made to sw2p1 and sw3p1.

In this scenario:

.---------.   .-----.   .-----.
|   sw1   +---+ sw2 +---+ sw3 |
'-1-2-3-4-'   '-1-2-'   '-1-2-'

When sw1p4 would leave a bridge, dsa_port_vlan_filtering would be
called for sw2 and sw3 with a non-existing port - leading to array
out-of-bounds accesses and crashes on mv88e6xxx.

Fixes: d371b7c92d19 ("net: dsa: Unset vlan_filtering when ports leave the bridge")
Signed-off-by: Tobias Waldekranz <tobias@...dekranz.com>
---
 net/dsa/switch.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/dsa/switch.c b/net/dsa/switch.c
index 9f9b70d6070a..517cc83d13cc 100644
--- a/net/dsa/switch.c
+++ b/net/dsa/switch.c
@@ -180,9 +180,11 @@ static int dsa_switch_bridge_leave(struct dsa_switch *ds,
 						info->sw_index, info->port,
 						info->bridge);
 
-	err = dsa_switch_sync_vlan_filtering(ds, info);
-	if (err)
-		return err;
+	if (ds->dst->index == info->tree_index && ds->index == info->sw_index) {
+		err = dsa_switch_sync_vlan_filtering(ds, info);
+		if (err)
+			return err;
+	}
 
 	return dsa_tag_8021q_bridge_leave(ds, info);
 }
-- 
2.25.1