linux-kernel - Re: [PATCH] net: mdio: Fix a double free issue in the .remove function

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Date:   Wed, 12 May 2021 22:44:03 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     andrew@...n.ch, hkallweit1@...il.com, davem@...emloft.net,
        kuba@...nel.org, david.daney@...ium.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] net: mdio: Fix a double free issue in the .remove
 function

On Wed, May 12, 2021 at 11:35:38PM +0200, Christophe JAILLET wrote:
> 'bus->mii_bus' have been allocated with 'devm_mdiobus_alloc_size()' in the
> probe function. So it must not be freed explicitly or there will be a
> double free.
> 
> Remove the incorrect 'mdiobus_free' in the remove function.

Yes, this looks correct, thanks.

Reviewed-by: Russell King <rmk+kernel@...linux.org.uk>

However, there's another issue in this driver that ought to be fixed.

If devm_mdiobus_alloc_size() succeeds, but of_mdiobus_register() fails,
we continue on to the next bus (which I think is reasonable.) We don't
free the bus.

When we come to the remove method however, we will call
mdiobus_unregister() on this existent but not-registered bus. Surely we
don't want to do that?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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