[PATCH net] net: dsa: microchip: Don't try to read stats for unused ports

[Robert Hancock]

If some of the switch ports were not listed in the device tree, due to
being unused, the ksz_mib_read_work function ended up accessing a NULL
dp->slave pointer and causing an oops. Skip checking statistics for any
unused ports.

Fixes: 7c6ff470aa867f53 ("net: dsa: microchip: add MIB counter reading
support")
Signed-off-by: Robert Hancock <hanc...@sedsystems.ca>
---
 drivers/net/dsa/microchip/ksz_common.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/dsa/microchip/ksz_common.c 
b/drivers/net/dsa/microchip/ksz_common.c
index 39dace8..f46086f 100644
--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c
@@ -83,6 +83,9 @@ static void ksz_mib_read_work(struct work_struct *work)
        int i;
 
        for (i = 0; i < dev->mib_port_cnt; i++) {
+               if (dsa_is_unused_port(dev->ds, i))
+                       continue;
+
                p = &dev->ports[i];
                mib = &p->mib;
                mutex_lock(&mib->cnt_mutex);
-- 
1.8.3.1