CVE-2026-74277: iommu/dma-iommu: Fix wrong scatterlist length assignment in P2PDMA path

CVE-2026-74277: iommu/dma-iommu: Fix wrong scatterlist length assignment in P2PDMA path

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

iommu/dma-iommu: Fix wrong scatterlist length assignment in P2PDMA path

In iommu_dma_map_sg(), when handling PCI P2PDMA cases, the DMA length
of the current scatterlist segment `s` is incorrectly assigned from the
head entry `sg->length` instead of the current entry `s->length`.

This typo causes all P2PDMA segments in the scatterlist to inherit the
length of the first segment, leading to corrupted DMA lengths for multi-
segment scatterlists.

Fix this by using `s->length` instead of `sg->length`.

The Linux kernel CVE team has assigned CVE-2026-74277 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.16 with commit a25e7962db0d79882c9d32fd2a67a02e79129c0e and fixed in 7.1.5 with commit 8646f00ce021e49f4f05bc1d4060a0c27b25d0e1
	Issue introduced in 6.16 with commit a25e7962db0d79882c9d32fd2a67a02e79129c0e and fixed in 7.2-rc1 with commit db50fb87015b955a5a0c155293b2dd40d63a3b9e

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-74277
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/iommu/dma-iommu.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/8646f00ce021e49f4f05bc1d4060a0c27b25d0e1
	https://git.kernel.org/stable/c/db50fb87015b955a5a0c155293b2dd40d63a3b9e