linux-kernel - Re: [PATCH net-next v1 1/1] net: usb: lan78xx: fix possible NULL pointer dereference in lan78xx_phy

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Message-ID: <aGOqIlnVGPce8GLT@pengutronix.de>
Date: Tue, 1 Jul 2025 11:28:02 +0200
From: Oleksij Rempel <o.rempel@...gutronix.de>
To: Paolo Abeni <pabeni@...hat.com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Woojung Huh <woojung.huh@...rochip.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Russell King <rmk+kernel@...linux.org.uk>,
	Thangaraj Samynathan <Thangaraj.S@...rochip.com>,
	Rengarajan Sundararajan <Rengarajan.S@...rochip.com>,
	Dan Carpenter <dan.carpenter@...aro.org>, kernel@...gutronix.de,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	UNGLinuxDriver@...rochip.com, Phil Elwell <phil@...pberrypi.org>,
	Maxime Chevallier <maxime.chevallier@...tlin.com>,
	Simon Horman <horms@...nel.org>
Subject: Re: [PATCH net-next v1 1/1] net: usb: lan78xx: fix possible NULL
 pointer dereference in lan78xx_phy_init()

On Tue, Jul 01, 2025 at 11:15:29AM +0200, Paolo Abeni wrote:
> On 6/26/25 12:37 PM, Oleksij Rempel wrote:
> > If no PHY device is found (e.g., for LAN7801 in fixed-link mode),
> > lan78xx_phy_init() may proceed to dereference a NULL phydev pointer,
> > leading to a crash.
> > 
> > Update the logic to perform MAC configuration first, then check for the presence
> > of a PHY. For the fixed-link case, set up the fixed link and return early,
> > bypassing any code that assumes a valid phydev pointer.
> > 
> > It is safe to move lan78xx_mac_prepare_for_phy() earlier because this function
> > only uses information from dev->interface, which is configured by
> > lan78xx_get_phy() beforehand. The function does not access phydev or any data
> > set up by later steps.
> > 
> > Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> > Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> 
> Looks good, but this IMHO deserves a Fixes tag - yep, even for net-next!
> 
> Could you please share it?

Fixes: e110bc825897 ("net: usb: lan78xx: Convert to PHYLINK for improved PHY and MAC management")

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