[PATCH] nvme-pci: fix parameter order in nvme_free_sgls() call

[PATCH] nvme-pci: fix parameter order in nvme_free_sgls() call

[Roger Pau Monne]

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@citrix.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?
---
 drivers/nvme/host/pci.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 0e4caeab739c..c8c5ed3eeac7 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -806,8 +806,8 @@ static void nvme_unmap_data(struct request *req)
 	if (!blk_rq_dma_unmap(req, dma_dev, &iod->dma_state, iod->total_len,
 			      map)) {
 		if (nvme_pci_cmd_use_sgl(&iod->cmd))
-			nvme_free_sgls(req, iod->descriptors[0],
-				       &iod->cmd.common.dptr.sgl, attrs);
+			nvme_free_sgls(req, &iod->cmd.common.dptr.sgl,
+			               iod->descriptors[0], attrs);
 		else
 			nvme_free_prps(req, attrs);
 	}
-- 
2.51.0

Re: [PATCH] nvme-pci: fix parameter order in nvme_free_sgls() call

[Christoph Hellwig]

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@citrix.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
that we should get into 6.19-rc and -stable ASAP.

The fix looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

but maybe we can reword the subject to sound less harmless, e.g.:

nvme-pci: DMA unmap the correct regions in nvme_free_sgls

?

Re: [PATCH] nvme-pci: fix parameter order in nvme_free_sgls() call

[Roger Pau Monné]

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@citrix.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@lst.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.

Re: [PATCH] nvme-pci: fix parameter order in nvme_free_sgls() call

[Christoph Hellwig]

On Wed, Jan 28, 2026 at 10:10:08AM +0100, Roger Pau Monné wrote:
> > > 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.

Yes, sorry.

Re: [PATCH] nvme-pci: fix parameter order in nvme_free_sgls() call

[Keith Busch]

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.

Thanks, applied to nvme-6.19 with updated subject.