netdev - [PATCH net] net: mscc: ocelot: fix use-after-free in ocelot_vlan

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Message-Id: <20220214234200.1594787-1-vladimir.oltean@nxp.com>
Date:   Tue, 15 Feb 2022 01:42:00 +0200
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com
Subject: [PATCH net] net: mscc: ocelot: fix use-after-free in ocelot_vlan_del()

ocelot_vlan_member_del() will free the struct ocelot_bridge_vlan, so if
this is the same as the port's pvid_vlan which we access afterwards,
what we're accessing is freed memory.

Fix the bug by determining whether to clear ocelot_port->pvid_vlan prior
to calling ocelot_vlan_member_del().

Fixes: d4004422f6f9 ("net: mscc: ocelot: track the port pvid using a pointer")
Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
 drivers/net/ethernet/mscc/ocelot.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/mscc/ocelot.c
index e6de86552df0..fd3ceb74620d 100644
--- a/drivers/net/ethernet/mscc/ocelot.c
+++ b/drivers/net/ethernet/mscc/ocelot.c
@@ -549,14 +549,18 @@ EXPORT_SYMBOL(ocelot_vlan_add);
 int ocelot_vlan_del(struct ocelot *ocelot, int port, u16 vid)
 {
 	struct ocelot_port *ocelot_port = ocelot->ports[port];
+	bool del_pvid = false;
 	int err;
 
+	if (ocelot_port->pvid_vlan && ocelot_port->pvid_vlan->vid == vid)
+		del_pvid = true;
+
 	err = ocelot_vlan_member_del(ocelot, port, vid);
 	if (err)
 		return err;
 
 	/* Ingress */
-	if (ocelot_port->pvid_vlan && ocelot_port->pvid_vlan->vid == vid)
+	if (del_pvid)
 		ocelot_port_set_pvid(ocelot, port, NULL);
 
 	/* Egress */
-- 
2.25.1