netdev - Re: [PATCH v2 net] net: phy: clear phydev->devlink when the link is deleted

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Message-ID: <2a856f0d-ca86-48d8-be67-e2edb20637bf@lunn.ch>
Date: Fri, 23 May 2025 15:18:32 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Wei Fang <wei.fang@....com>
Cc: hkallweit1@...il.com, linux@...linux.org.uk, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	f.fainelli@...il.com, xiaolei.wang@...driver.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	imx@...ts.linux.dev
Subject: Re: [PATCH v2 net] net: phy: clear phydev->devlink when the link is
 deleted

On Fri, May 23, 2025 at 04:37:59PM +0800, Wei Fang wrote:
> There is a potential crash issue when disabling and re-enabling the
> network port. When disabling the network port, phy_detach() calls
> device_link_del() to remove the device link, but it does not clear
> phydev->devlink, so phydev->devlink is not a NULL pointer. Then the
> network port is re-enabled, but if phy_attach_direct() fails before
> calling device_link_add(), the code jumps to the "error" label and
> calls phy_detach(). Since phydev->devlink retains the old value from
> the previous attach/detach cycle, device_link_del() uses the old value,
> which accesses a NULL pointer and causes a crash. The simplified crash
> log is as follows.
> 
> [   24.702421] Call trace:
> [   24.704856]  device_link_put_kref+0x20/0x120
> [   24.709124]  device_link_del+0x30/0x48
> [   24.712864]  phy_detach+0x24/0x168
> [   24.716261]  phy_attach_direct+0x168/0x3a4
> [   24.720352]  phylink_fwnode_phy_connect+0xc8/0x14c
> [   24.725140]  phylink_of_phy_connect+0x1c/0x34
> 
> Therefore, phydev->devlink needs to be cleared when the device link is
> deleted.
> 
> Fixes: bc66fa87d4fd ("net: phy: Add link between phy dev and mac dev")
> Signed-off-by: Wei Fang <wei.fang@....com>

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew