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

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Date:   Wed, 4 May 2022 14:03:08 -0300
From:   Fabio Estevam <festevam@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        netdev <netdev@...r.kernel.org>,
        Oleksij Rempel <o.rempel@...gutronix.de>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Fabio Estevam <festevam@...x.de>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH net v2 1/2] net: phy: micrel: Do not use
 kszphy_suspend/resume for KSZ8061

Hi Andrew,

On Wed, May 4, 2022 at 11:31 AM Fabio Estevam <festevam@...il.com> wrote:
>
> 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).

If this series gets applied, I plan to submit two patches targeting net-next to:

1. Allow .probe to be called without .data_driver being passed
2. Convert KSZ8061 to use .probe and kszphy_suspend/resume