netdev - Re: [PATCH net] net: phy: fix potential use of NULL pointer in phy

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Message-ID: <d5964682-0f5a-4b9e-8415-bf306f18b8b1@lunn.ch>
Date: Fri, 28 Jun 2024 16:12:36 +0200
From: Andrew Lunn <andrew@...n.ch>
To: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
Cc: Heiner Kallweit <hkallweit1@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org
Subject: Re: [PATCH net] net: phy: fix potential use of NULL pointer in
 phy_suspend()

On Fri, Jun 28, 2024 at 11:32:11AM +0100, Russell King (Oracle) wrote:
> phy_suspend() checks the WoL status, and then dereferences
> phydrv->flags if (and only if) we decided that WoL has been enabled
> on either the PHY or the netdev.
> 
> We then check whether phydrv was NULL, but we've potentially already
> dereferenced the pointer.
> 
> If phydrv is NULL, then phy_ethtool_get_wol() will return an error
> and leave wol.wolopts set to zero. However, if netdev->wol_enabled
> is true, then we would dereference a NULL pointer.
> 
> Checking the PHY drivers, the only place that phydev->wol_enabled is
> checked by them is in their suspend/resume callbacks and nowhere else
> (which is correct, because phylib only updates this in phy_suspend()).
> 
> So, move the NULL pointer check earlier to avoid a NULL pointer
> dereference. Leave the check for phydrv->suspend in place as a driver
> may populate the .resume method but not the .suspend method.
> 
> Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>

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

As you say, nobody has reported this. So i think net-next is
sufficient.

    Andrew