netdev - [PATCH net 5/5] net: dsa: sja1105: block FDB accesses that are concurrent with a switch reset

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Message-Id: <20230908133352.2007218-6-vladimir.oltean@nxp.com>
Date: Fri,  8 Sep 2023 16:33:52 +0300
From: Vladimir Oltean <vladimir.oltean@....com>
To: netdev@...r.kernel.org
Cc: Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Xiaoliang Yang <xiaoliang.yang_1@....com>,
	Andrew Lunn <andrew@...n.ch>,
	Florian Fainelli <f.fainelli@...il.com>,
	Yanan Yang <yanan.yang@....com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH net 5/5] net: dsa: sja1105: block FDB accesses that are concurrent with a switch reset

Currently, when we add the first sja1105 port to a bridge with
vlan_filtering 1, then we sometimes see this output:

sja1105 spi2.2: port 4 failed to read back entry for be:79:b4:9e:9e:96 vid 3088: -ENOENT
sja1105 spi2.2: Reset switch and programmed static config. Reason: VLAN filtering
sja1105 spi2.2: port 0 failed to add be:79:b4:9e:9e:96 vid 0 to fdb: -2

It is because sja1105_fdb_add() runs from the dsa_owq which is no longer
serialized with switch resets since it dropped the rtnl_lock() in the
blamed commit.

Either performing the FDB accesses before the reset, or after the reset,
is equally fine, because sja1105_static_fdb_change() backs up those
changes in the static config, but FDB access during reset isn't ok.

Make sja1105_static_config_reload() take the fdb_lock to fix that.

Fixes: 0faf890fc519 ("net: dsa: drop rtnl_lock from dsa_slave_switchdev_event_work")
Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
 drivers/net/dsa/sja1105/sja1105_main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/dsa/sja1105/sja1105_main.c b/drivers/net/dsa/sja1105/sja1105_main.c
index cefd72617af4..1a367e64bc3b 100644
--- a/drivers/net/dsa/sja1105/sja1105_main.c
+++ b/drivers/net/dsa/sja1105/sja1105_main.c
@@ -2297,6 +2297,7 @@ int sja1105_static_config_reload(struct sja1105_private *priv,
 	int rc, i;
 	s64 now;
 
+	mutex_lock(&priv->fdb_lock);
 	mutex_lock(&priv->mgmt_lock);
 
 	mac = priv->static_config.tables[BLK_IDX_MAC_CONFIG].entries;
@@ -2409,6 +2410,7 @@ int sja1105_static_config_reload(struct sja1105_private *priv,
 		goto out;
 out:
 	mutex_unlock(&priv->mgmt_lock);
+	mutex_unlock(&priv->fdb_lock);
 
 	return rc;
 }
-- 
2.34.1