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

From: "Michael Walle" <mwalle@kernel.org>
To: "Romli, Khairul Anuar" <khairul.anuar.romli@altera.com>,
	"Tudor Ambarus" <tudor.ambarus@linaro.org>,
	"Pratyush Yadav" <pratyush@kernel.org>,
	"Miquel Raynal" <miquel.raynal@bootlin.com>,
	"Richard Weinberger" <richard@nod.at>,
	"Vignesh Raghavendra" <vigneshr@ti.com>,
	"open list:SPI NOR SUBSYSTEM" <linux-mtd@lists.infradead.org>,
	"open list" <linux-kernel@vger.kernel.org>,
	"Gerlach, Matthew" <matthew.gerlach@altera.com>
Subject: Re: [PATCH 1/1] mtd: spi-nor: core: Prevent oops during driver removal with active read or write operations
Date: Wed, 16 Jul 2025 08:46:02 +0200	[thread overview]
Message-ID: <DBD9ZQ7GV4YY.PLA885RZGBDV@kernel.org> (raw)
In-Reply-To: < <BY5PR03MB5299D68304D916F466837E6BC657A@BY5PR03MB5299.namprd03.prod.outlook.com>

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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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