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Date:   Thu, 16 Jan 2020 19:46:28 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     davem@...emloft.net, linux@...linux.org.uk, andrew@...n.ch,
        f.fainelli@...il.com, hkallweit1@...il.com
Cc:     netdev@...r.kernel.org,
        Alex Marginean <alexandru.marginean@....com>
Subject: [PATCH net-next] net: phy: don't crash in phy_read/_write_mmd without a PHY driver

From: Alex Marginean <alexandru.marginean@....com>

The APIs can be used by Ethernet drivers without actually loading a PHY
driver. This may become more widespread in the future with 802.3z
compatible MAC PCS devices being locally driven by the MAC driver when
configuring for a PHY mode with in-band negotiation.

Check that drv is not NULL before reading from it.

Signed-off-by: Alex Marginean <alexandru.marginean@....com>
---
If this hasn't been reported by now I assume it wasn't an issue so far.
So I've targeted the patch for net-next and not provided a Fixes: tag.

 drivers/net/phy/phy-core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/phy/phy-core.c b/drivers/net/phy/phy-core.c
index 769a076514b0..a4d2d59fceca 100644
--- a/drivers/net/phy/phy-core.c
+++ b/drivers/net/phy/phy-core.c
@@ -387,7 +387,7 @@ int __phy_read_mmd(struct phy_device *phydev, int devad, u32 regnum)
 	if (regnum > (u16)~0 || devad > 32)
 		return -EINVAL;
 
-	if (phydev->drv->read_mmd) {
+	if (phydev->drv && phydev->drv->read_mmd) {
 		val = phydev->drv->read_mmd(phydev, devad, regnum);
 	} else if (phydev->is_c45) {
 		u32 addr = MII_ADDR_C45 | (devad << 16) | (regnum & 0xffff);
@@ -444,7 +444,7 @@ int __phy_write_mmd(struct phy_device *phydev, int devad, u32 regnum, u16 val)
 	if (regnum > (u16)~0 || devad > 32)
 		return -EINVAL;
 
-	if (phydev->drv->write_mmd) {
+	if (phydev->drv && phydev->drv->write_mmd) {
 		ret = phydev->drv->write_mmd(phydev, devad, regnum, val);
 	} else if (phydev->is_c45) {
 		u32 addr = MII_ADDR_C45 | (devad << 16) | (regnum & 0xffff);
-- 
2.17.1

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