netdev - [PATCH net-next] net: dsa: fix oops while probing Marvell DSA switches

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Message-Id: <E1jJHhw-0004UO-OJ@rmk-PC.armlinux.org.uk>
Date:   Tue, 31 Mar 2020 15:17:36 +0100
From:   Russell King <rmk+kernel@...linux.org.uk>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>, ioana.ciornei@....com,
        olteanv@...il.com, Vivien Didelot <vivien.didelot@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org
Subject: [PATCH net-next] net: dsa: fix oops while probing Marvell DSA
 switches

Fix an oops in dsa_port_phylink_mac_change() caused by a combination
of a20f997010c4 ("net: dsa: Don't instantiate phylink for CPU/DSA
ports unless needed") and the net-dsa-improve-serdes-integration
series of patches 65b7a2c8e369 ("Merge branch
'net-dsa-improve-serdes-integration'").

Unable to handle kernel NULL pointer dereference at virtual address 00000124
pgd = c0004000
[00000124] *pgd=00000000
Internal error: Oops: 805 [#1] SMP ARM
Modules linked in: tag_edsa spi_nor mtd xhci_plat_hcd mv88e6xxx(+) xhci_hcd armada_thermal marvell_cesa dsa_core ehci_orion libdes phy_armada38x_comphy at24 mcp3021 sfp evbug spi_orion sff mdio_i2c
CPU: 1 PID: 214 Comm: irq/55-mv88e6xx Not tainted 5.6.0+ #470
Hardware name: Marvell Armada 380/385 (Device Tree)
PC is at phylink_mac_change+0x10/0x88
LR is at mv88e6352_serdes_irq_status+0x74/0x94 [mv88e6xxx]

Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
---
This problem only exists when the above patch and series are merged
together.

 net/dsa/slave.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 84dda24b7231..92a8131651cf 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -1245,7 +1245,8 @@ void dsa_port_phylink_mac_change(struct dsa_switch *ds, int port, bool up)
 {
 	const struct dsa_port *dp = dsa_to_port(ds, port);
 
-	phylink_mac_change(dp->pl, up);
+	if (dp->pl)
+		phylink_mac_change(dp->pl, up);
 }
 EXPORT_SYMBOL_GPL(dsa_port_phylink_mac_change);
 
-- 
2.20.1