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

[Greg Kroah-Hartman]

From: Robert Hancock <hancock@xxxxxxxxxxxxx>

[ 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 <hancock@xxxxxxxxxxxxx>
Reviewed-by: Vivien Didelot <vivien.didelot@xxxxxxxxx>
Reviewed-by: Andrew Lunn <andrew@xxxxxxx>
Reviewed-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 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);