linux-kernel - Re: [PATCH V1] nvme-pci: Fix NULL pointer dereference in nvme_pci_prp_iter

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Message-ID: <aYGSP4luf1nOFhS2@kbusch-mbp>
Date: Mon, 2 Feb 2026 23:14:23 -0700
From: Keith Busch <kbusch@...nel.org>
To: Christoph Hellwig <hch@....de>
Cc: Robin Murphy <robin.murphy@....com>,
	Pradeep P V K <pradeep.pragallapati@....qualcomm.com>,
	axboe@...nel.dk, sagi@...mberg.me, linux-nvme@...ts.infradead.org,
	linux-kernel@...r.kernel.org, nitin.rawat@....qualcomm.com,
	Leon Romanovsky <leon@...nel.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>, iommu@...ts.linux.dev
Subject: Re: [PATCH V1] nvme-pci: Fix NULL pointer dereference in
 nvme_pci_prp_iter_next

On Tue, Feb 03, 2026 at 06:27:56AM +0100, Christoph Hellwig wrote:
> >  	iod->nr_descriptors = 0;
> >  	iod->total_len = 0;
> >  	iod->meta_total_len = 0;
> > +	iod->nr_dma_vecs = 0;
> > +	iod->dma_vecs = NULL;
> 
> I don't think we need the dma_vecs initialization here, as everything
> is keyed off nr_dma_vecs.

Yes, we should definitely use nr_dma_vecs and skip the NULL setting. I'm
a big fan removing unnecessary initialisations. Just a caution, my
suggested patch has this check:

	if (!iod->dma_vecs)

So we just need to update it to use 'iod->nr_dma_vecs' instead, which
would have been correct, too.