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

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Message-ID: <e8b5259f-02e3-42c5-a872-c39fb8c7fd13@lunn.ch>
Date: Wed, 21 Jun 2023 17:01:11 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Florian Fainelli <f.fainelli@...il.com>
Cc: netdev <netdev@...r.kernel.org>, Heiner Kallweit <hkallweit1@...il.com>,
	ansuelsmth@...il.com, Russell King <rmk+kernel@...linux.org.uk>,
	stable@...r.kernel.org
Subject: Re: [PATCH net] net: phy: Manual remove LEDs to ensure correct
 ordering

> 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

Yes, i was not expecting this patch to fix that. But i was getting the
NULL pointer dereference you pointed out with another setup, and this
change does fix that part of the problem.

> still not clear to me how the workqueue managed to execute and not finish
> before we unregistered the PHY device.

Me neither. I took a look at the MDIO bus driver and could not see
anything obvious. I think you are going to have to scatter printk() in
the code to get a clear understanding of the order things are done.
Maybe it is another devm_ timing issue.

      Andrew