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Date:   Wed, 9 Aug 2023 16:15:42 +0200
From:   hch <hch@lst.de>
To:     Stephan Wurm <stephan.wurm@a-eberle.de>
Cc:     hch <hch@lst.de>, Richard Weinberger <richard@nod.at>,
        linux-block <linux-block@vger.kernel.org>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
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        linux-kernel <linux-kernel@vger.kernel.org>,
        Johannes Eigner <johannes.eigner@a-eberle.de>
Subject: Re: ubiblock: null pointer dereference using scatterlist in
 work_queue
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On Wed, Aug 09, 2023 at 04:10:59PM +0200, Stephan Wurm wrote:
> Am 09. Aug 15:53 hat hch geschrieben:
> > Well, a scatterlist culd contain a highmem page, in which case sg_virt
> > isn't going to cut it and you need to kmap.  Is this a 32-bit system
> > with highmem enabled?
> I can confirm it is a 32-bit system with highmem enabled.

Yes.  So the code needs to stop using sg_virt to work on highmem
setups and do the equivalent of scsi_kmap_atomic_sg.  Best way
forward is probably to move scsi_kmap_atomic_sg to lib/scatterlist.c
(and also convert it to kmap_local instead of kmap_atomic while you're
at it) and then use that in ubiblock