netdev - [PATCH net] net: phy: dp83822: Fix null pointer access on DP83825/DP83826 devices

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Date:   Wed, 25 Jan 2023 19:23:26 +0100
From:   Andre Kalb <svc.sw.rte.linux@....de>
To:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Felix Riemann <felix.riemann@....de>
Subject: [PATCH net] net: phy: dp83822: Fix null pointer access on
 DP83825/DP83826 devices

From: Andre Kalb <andre.kalb@....de>

The probe() function is only used for the DP83822 PHY, leaving the
private data pointer uninitialized for the smaller DP83825/26 models.
While all uses of the private data structure are hidden in 82822 specific
callbacks, configuring the interrupt is shared across all models.
This causes a NULL pointer dereference on the smaller PHYs as it accesses
the private data unchecked. Verifying the pointer avoids that.

Fixes: 5dc39fd5ef35 ("net: phy: DP83822: Add ability to advertise Fiber connection")
Signed-off-by: Andre Kalb <andre.kalb@....de>
---
 drivers/net/phy/dp83822.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/phy/dp83822.c b/drivers/net/phy/dp83822.c
index 0b511abb5422..f070aa97c77b 100644
--- a/drivers/net/phy/dp83822.c
+++ b/drivers/net/phy/dp83822.c
@@ -232,7 +232,8 @@ static int dp83822_config_intr(struct phy_device *phydev)
 				DP83822_ENERGY_DET_INT_EN |
 				DP83822_LINK_QUAL_INT_EN);
 
-		if (!dp83822->fx_enabled)
+		/* Private data pointer is NULL on DP83825/26 */
+		if (!dp83822 || !dp83822->fx_enabled)
 			misr_status |= DP83822_ANEG_COMPLETE_INT_EN |
 				       DP83822_DUP_MODE_CHANGE_INT_EN |
 				       DP83822_SPEED_CHANGED_INT_EN;
@@ -252,7 +253,8 @@ static int dp83822_config_intr(struct phy_device *phydev)
 				DP83822_PAGE_RX_INT_EN |
 				DP83822_EEE_ERROR_CHANGE_INT_EN);
 
-		if (!dp83822->fx_enabled)
+		/* Private data pointer is NULL on DP83825/26 */
+		if (!dp83822 || !dp83822->fx_enabled)
 			misr_status |= DP83822_ANEG_ERR_INT_EN |
 				       DP83822_WOL_PKT_INT_EN;
 
-- 
2.35.3