linux-kernel - Re: [PATCH 1/1] mtd: spi-nor: core: Prevent oops during driver removal with active read or write operations

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Message-Id: <DBD9ZQ7GV4YY.PLA885RZGBDV@kernel.org>
Date: Wed, 16 Jul 2025 08:46:02 +0200
From: "Michael Walle" <mwalle@...nel.org>
To: "Romli, Khairul Anuar" <khairul.anuar.romli@...era.com>, "Tudor Ambarus"
 <tudor.ambarus@...aro.org>, "Pratyush Yadav" <pratyush@...nel.org>, "Miquel
 Raynal" <miquel.raynal@...tlin.com>, "Richard Weinberger" <richard@....at>,
 "Vignesh Raghavendra" <vigneshr@...com>, "open list:SPI NOR SUBSYSTEM"
 <linux-mtd@...ts.infradead.org>, "open list"
 <linux-kernel@...r.kernel.org>, "Gerlach, Matthew"
 <matthew.gerlach@...era.com>
Subject: Re: [PATCH 1/1] mtd: spi-nor: core: Prevent oops during driver
 removal with active read or write operations

Hi,

On Tue Jul 15, 2025 at 9:53 AM CEST, Khairul Anuar Romli wrote:
> > > -     module_put(dev->driver->owner);
> > > +     if (dev && dev->driver && dev->driver->owner)
> > > +             module_put(dev->driver->owner);
> > 
> > Why is dev->driver or dev->driver->owner NULL in the first place?
>
> When we remove/unbind the the spi node during busy, we will hit
> with dev->driver and dev->driver->owner NULL derefence.

Yes, but my question was why is this the case? I.e. why is
dev or dev->driver NULL?

-michael

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