[PATCH 5.1 21/98] net: dsa: microchip: Dont try to read stats for unused ports

[Greg Kroah-Hartman]

From: Robert Hancock <hanc...@sedsystems.ca>

[ Upstream commit 6bb9e376c2a4cc5120c3bf5fd3048b9a0a6ec1f8 ]

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>
Reviewed-by: Vivien Didelot <vivien.dide...@gmail.com>
Reviewed-by: Andrew Lunn <and...@lunn.ch>
Reviewed-by: Florian Fainelli <f.faine...@gmail.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/net/dsa/microchip/ksz_common.c |    3 +++
 1 file changed, 3 insertions(+)

--- 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 wor
        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);