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Message-Id: <DBP84FIUUQO7.369TFNTJFELMW@kernel.org>
Date: Wed, 30 Jul 2025 09:50:07 +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 v3 1/1] mtd: spi-nor: core: Prevent oops during driver
removal with active read or write operations
Hi,
> > On Wed Jul 30, 2025 at 3:39 AM CEST, Khairul Anuar Romli wrote:
> > > From: kromli <khairul.anuar.romli@...era.com>
> > >
> > > Ensure that the pointer passed to module_put() in spi_nor_put_device()
> > > is not NULL before use. This change adds a guard clause to return
> > > early, preventing the kernel crash below when the cadence-qspi driver
> > > is removed during a dd operation:
> >
> > As already asked in v2. This needs a (more detailed) description what is going
> > on and what is going wrong.
> >
> > -michael
>
> Hi,
>
> We just run the following test we observe the crash.
>
> time dd if=/dev/mtd1 of=out.img bs=1MB count=1000 &
> echo spi0.0 > /sys/bus/spi/drivers/spi-nor/unbind
> echo spi0.0 > /sys/bus/spi/drivers/spi-nor/bind
>
> From the observation, the dd is not entirely terminated when the unbind took place.
> Maybe there is other changes require to ensure the dd operation gets terminated
> when driver unbind/remove.
I'd expect an analysis what's going wrong in the kernel to judge the
correctness of the patch.
Thanks,
-michael
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