linux-kernel - Re: [PATCH] nvme-pci: fix parameter order in nvme_free

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Message-ID: <aXnScGiFkX7ZFFdE@Mac.lan>
Date: Wed, 28 Jan 2026 10:10:08 +0100
From: Roger Pau Monné <roger.pau@...rix.com>
To: Christoph Hellwig <hch@....de>
Cc: xen-devel@...ts.xenproject.org, Jens Axboe <axboe@...nel.dk>,
	Keith Busch <kbusch@...nel.org>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Sagi Grimberg <sagi@...mberg.me>
Subject: Re: [PATCH] nvme-pci: fix parameter order in nvme_free_sgls() call

On Wed, Jan 28, 2026 at 09:49:58AM +0100, Christoph Hellwig wrote:
> On Tue, Jan 27, 2026 at 08:59:06PM +0100, Roger Pau Monne wrote:
> > The call to nvme_free_sgls() in nvme_unmap_data() has the sg_list and sge
> > parameters swapped.  This wasn't noticed by the compiler because both share
> > the same type.  On a Xen PV hardware domain, and possibly any other
> > architectures that takes that path, this leads to corruption of the NVMe
> > contents.
> > 
> > Fixes: f0887e2a52d4 ("nvme-pci: create common sgl unmapping helper")
> > Signed-off-by: Roger Pau Monné <roger.pau@...rix.com>
> > ---
> > If possible it would be good for this to go in 6.19.0-rc8, as corruption of
> > the root device as part of a kernel update is unexpected. Sadly 6.18
> > already contained this issue, and no-one noticed, so its impact is limited?
> 
> This only affects non-IOMMU paths with a non-noop dma_unmap_phys.
> So it is a very common setup, but very severe for those.  Because of

Do you mean a "not very common setup"?  Otherwise I can't parse the
sentence.

> that we should get into 6.19-rc and -stable ASAP.
> 
> The fix looks good:
> 
> Reviewed-by: Christoph Hellwig <hch@....de>

Thanks.

> but maybe we can reword the subject to sound less harmless, e.g.:
> 
> nvme-pci: DMA unmap the correct regions in nvme_free_sgls

Fine with me.  I think I was more focused on describing the logical
change rather that the actual effect of it.  Can you adjust it when
picking up?

Regards, Roger.