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

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Message-ID: <20260203062334.GI16426@lst.de>
Date: Tue, 3 Feb 2026 07:23:34 +0100
From: Christoph Hellwig <hch@....de>
To: Keith Busch <kbusch@...nel.org>
Cc: Christoph Hellwig <hch@....de>, 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 Mon, Feb 02, 2026 at 11:14:23PM -0700, Keith Busch wrote:
> 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.

Ah, right.