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: <7c9c7be7-af3c-4f40-80b4-5b420ebbfca3@redhat.com>
Date: Tue, 1 Jul 2025 11:15:29 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Oleksij Rempel <o.rempel@...gutronix.de>,
 "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>
Cc: 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 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?

Thanks,

Paolo