netdev - Re: [PATCH net] net: phy: Manual remove LEDs to ensure correct ordering

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Date: Wed, 21 Jun 2023 18:52:56 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Florian Fainelli <f.fainelli@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>, netdev <netdev@...r.kernel.org>,
	Heiner Kallweit <hkallweit1@...il.com>, ansuelsmth@...il.com,
	stable@...r.kernel.org
Subject: Re: [PATCH net] net: phy: Manual remove LEDs to ensure correct
 ordering

On Wed, Jun 21, 2023 at 06:12:40PM +0100, Florian Fainelli wrote:
> Hi Russell,
> 
> On 6/21/2023 6:04 PM, Russell King (Oracle) wrote:
> > On Wed, Jun 21, 2023 at 03:04:14PM +0100, Florian Fainelli wrote:
> > > Hi Andrew,
> > > 
> > > On 6/17/2023 4:55 PM, Andrew Lunn wrote:
> > > > If the core is left to remove the LEDs via devm_, it is performed too
> > > > late, after the PHY driver is removed from the PHY. This results in
> > > > dereferencing a NULL pointer when the LED core tries to turn the LED
> > > > off before destroying the LED.
> > > > 
> > > > Manually unregister the LEDs at a safe point in phy_remove.
> > > > 
> > > > Cc: stable@...r.kernel.org
> > > > Reported-by: Florian Fainelli <f.fainelli@...il.com>
> > > > Suggested-by: Florian Fainelli <f.fainelli@...il.com>
> > > > Fixes: 01e5b728e9e4 ("net: phy: Add a binding for PHY LEDs")
> > > > Signed-off-by: Andrew Lunn <andrew@...n.ch>
> > > 
> > > Thanks for fixing this, this is an improvement, though I can still hit
> > > another sort of use after free whereby the GENET driver removes the
> > > mdio-bcm-unimac platform device and eventually cuts the clock to the MDIO
> > > block thus causing the following:
> > 
> > Hi Florian,
> > 
> > Can you try setting trigger_data->led_cdev to NULL after the
> > cancel_delayed_work_sync() in netdev_trig_deactivate() and see
> > what the effect is?
> 
> Thanks for the suggestion, getting an identical trace as before with that
> change.

Thanks for trying. I was wondering whether the work was being re-queued
after the flush_work(), but seemingly not.

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