[PATCH 5.4 339/389] net: dsa: mv88e6060: prevent crash on an unused port

Greg Kroah-Hartman
2022-08-23T11:55:19Z

From: Sergei Antonov <saproj@gmail.com>

commit 246bbf2f977ea36aaf41f5d24370fef433250728 upstream.

If the port isn't a CPU port nor a user port, 'cpu_dp'
is a null pointer and a crash happened on dereferencing
it in mv88e6060_setup_port():

[ 9.575872] Unable to handle kernel NULL pointer dereference at virtual address 00000014
...
[ 9.942216] mv88e6060_setup from dsa_register_switch+0x814/0xe84
[ 9.948616] dsa_register_switch from mdio_probe+0x2c/0x54
[ 9.954433] mdio_probe from really_probe.part.0+0x98/0x2a0
[ 9.960375] really_probe.part.0 from driver_probe_device+0x30/0x10c
[ 9.967029] driver_probe_device from __device_attach_driver+0xb8/0x13c
[ 9.973946] __device_attach_driver from bus_for_each_drv+0x90/0xe0
[ 9.980509] bus_for_each_drv from __device_attach+0x110/0x184
[ 9.986632] __device_attach from bus_probe_device+0x8c/0x94
[ 9.992577] bus_probe_device from deferred_probe_work_func+0x78/0xa8
[ 9.999311] deferred_probe_work_func from process_one_work+0x290/0x73c
[ 10.006292] process_one_work from worker_thread+0x30/0x4b8
[ 10.012155] worker_thread from kthread+0xd4/0x10c
[ 10.017238] kthread from ret_from_fork+0x14/0x3c

Fixes: 0abfd494deef ("net: dsa: use dedicated CPU port")
CC: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
CC: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Sergei Antonov <saproj@gmail.com>
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://lore.kernel.org/r/20220811070939.1717146-1-saproj@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/dsa/mv88e6060.c | 3 +++
1 file changed, 3 insertions(+)

--- a/drivers/net/dsa/mv88e6060.c
+++ b/drivers/net/dsa/mv88e6060.c
@@ -117,6 +117,9 @@ static int mv88e6060_setup_port(struct m
int addr = REG_PORT(p);
int ret;

+ if (dsa_is_unused_port(priv->ds, p))
+ return 0;
+
/* Do not force flow control, disable Ingress and Egress
* Header tagging, disable VLAN tunneling, and set the port
* state to Forwarding. Additionally, if this is the CPU