netdev - [PATCH net v2 1/2] net: phy: micrel: Do not use kszphy

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Date:   Wed,  4 May 2022 11:31:03 -0300
From:   Fabio Estevam <festevam@...il.com>
To:     kuba@...nel.org
Cc:     davem@...emloft.net, andrew@...n.ch, claudiu.beznea@...rochip.com,
        netdev@...r.kernel.org, o.rempel@...gutronix.de,
        linux@...linux.org.uk, Fabio Estevam <festevam@...x.de>,
        stable@...r.kernel.org
Subject: [PATCH net v2 1/2] net: phy: micrel: Do not use kszphy_suspend/resume for KSZ8061

From: Fabio Estevam <festevam@...x.de>

Since commit f1131b9c23fb ("net: phy: micrel: use
kszphy_suspend()/kszphy_resume for irq aware devices") the following
NULL pointer dereference is observed on a board with KSZ8061:

 # udhcpc -i eth0
udhcpc: started, v1.35.0
8<--- cut here ---
Unable to handle kernel NULL pointer dereference at virtual address 00000008
pgd = f73cef4e
[00000008] *pgd=00000000
Internal error: Oops: 5 [#1] SMP ARM
Modules linked in:
CPU: 0 PID: 196 Comm: ifconfig Not tainted 5.15.37-dirty #94
Hardware name: Freescale i.MX6 SoloX (Device Tree)
PC is at kszphy_config_reset+0x10/0x114
LR is at kszphy_resume+0x24/0x64
...

The KSZ8061 phy_driver structure does not have the .probe/..driver_data
fields, which means that priv is not allocated.

This causes the NULL pointer dereference inside kszphy_config_reset().

Fix the problem by using the generic suspend/resume functions as before.

Another alternative would be to provide the .probe and .driver_data
information into the structure, but to be on the safe side, let's
just restore Ethernet functionality by using the generic suspend/resume.

Cc: stable@...r.kernel.org
Fixes: f1131b9c23fb ("net: phy: micrel: use kszphy_suspend()/kszphy_resume for irq aware devices")
Signed-off-by: Fabio Estevam <festevam@...x.de>
---
Changes since v1:
- Explained why enphy_suspend/resume solution is preferred (Andrew).

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

diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
index 685a0ab5453c..11cd073630e5 100644
--- a/drivers/net/phy/micrel.c
+++ b/drivers/net/phy/micrel.c
@@ -3021,8 +3021,8 @@ static struct phy_driver ksphy_driver[] = {
 	.config_init	= ksz8061_config_init,
 	.config_intr	= kszphy_config_intr,
 	.handle_interrupt = kszphy_handle_interrupt,
-	.suspend	= kszphy_suspend,
-	.resume		= kszphy_resume,
+	.suspend	= genphy_suspend,
+	.resume		= genphy_resume,
 }, {
 	.phy_id		= PHY_ID_KSZ9021,
 	.phy_id_mask	= 0x000ffffe,
-- 
2.25.1