[PATCH net] net: phy: guard against accessing a NULL features bitmap

[Camelia Groza]

Since phy driver features became a link_mode bitmap, phy drivers that
don't have a list of features configured will cause the kernel to crash
when probed.

Fixes: 719655a14971 ("net: phy: Replace phy driver features u32 with link_mode bitmap")
Reported-by: Scott Wood <oss@xxxxxxxxxxxx>
Signed-off-by: Camelia Groza <camelia.groza@xxxxxxx>
---
I'll submit a modified version of this patch to 4.20 stable once this
one is accepted.
---
 drivers/net/phy/phy_device.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 5199000..ddf04ab 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -2154,7 +2154,8 @@ static int phy_probe(struct device *dev)
 	 * a controller will attach, and may modify one
 	 * or both of these values
 	 */
-	linkmode_copy(phydev->supported, phydrv->features);
+	if (phydrv->features)
+		linkmode_copy(phydev->supported, phydrv->features);
 	of_set_phy_supported(phydev);
 	linkmode_copy(phydev->advertising, phydev->supported);
 
@@ -2174,8 +2175,9 @@ static int phy_probe(struct device *dev)
 	 * (e.g. hardware erratum) where the driver wants to set only one
 	 * of these bits.
 	 */
-	if (test_bit(ETHTOOL_LINK_MODE_Pause_BIT, phydrv->features) ||
-	    test_bit(ETHTOOL_LINK_MODE_Asym_Pause_BIT, phydrv->features)) {
+	if (phydrv->features &&
+	    (test_bit(ETHTOOL_LINK_MODE_Pause_BIT, phydrv->features) ||
+	     test_bit(ETHTOOL_LINK_MODE_Asym_Pause_BIT, phydrv->features))) {
 		linkmode_clear_bit(ETHTOOL_LINK_MODE_Pause_BIT,
 				   phydev->supported);
 		linkmode_clear_bit(ETHTOOL_LINK_MODE_Asym_Pause_BIT,
-- 
1.9.1