Re: [PATCH net v2 1/2] net: phy: micrel: Do not use kszphy_suspend/resume for KSZ8061

From: Fabio Estevam <festevam@gmail.com>
To: Jakub Kicinski <kuba@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>,
	Andrew Lunn <andrew@lunn.ch>,
	Claudiu Beznea <claudiu.beznea@microchip.com>,
	netdev <netdev@vger.kernel.org>,
	Oleksij Rempel <o.rempel@pengutronix.de>,
	Russell King - ARM Linux <linux@armlinux.org.uk>,
	Fabio Estevam <festevam@denx.de>, stable <stable@vger.kernel.org>
Subject: Re: [PATCH net v2 1/2] net: phy: micrel: Do not use kszphy_suspend/resume for KSZ8061
Date: Wed, 4 May 2022 14:03:08 -0300	[thread overview]
Message-ID: <CAOMZO5DU8XRCGaYOcGeHimgupqMksyLXsjL=R8JHajSBs4KAeg@mail.gmail.com> (raw)
In-Reply-To: <20220504143104.1286960-1-festevam@gmail.com>

Hi Andrew,

On Wed, May 4, 2022 at 11:31 AM Fabio Estevam <festevam@gmail.com> wrote:
>
> From: Fabio Estevam <festevam@denx.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@vger.kernel.org
> Fixes: f1131b9c23fb ("net: phy: micrel: use kszphy_suspend()/kszphy_resume for irq aware devices")
> Signed-off-by: Fabio Estevam <festevam@denx.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