CVE-2026-80958: dm-pcache: clamp the tail kset read to the segment data region

CVE-2026-80958: dm-pcache: clamp the tail kset read to the segment data region

[Greg Kroah-Hartman]

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

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

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

dm-pcache: clamp the tail kset read to the segment data region

The tail-kset read in cache_replay(), the writeback worker and the GC
worker bounds its length by PCACHE_SEG_SIZE - seg_off, the raw segment
size rather than the data region. A tail near the segment end reads past
the segment data into the following control area.

Clamp the read to cache_seg_remain(), the data region.

The Linux kernel CVE team has assigned CVE-2026-80958 to this issue.


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

	Issue introduced in 6.18 with commit 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 and fixed in 6.18.50 with commit 2cd9776fe3f2d88ec22c36d3c8ba09fbf9d5500c
	Issue introduced in 6.18 with commit 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 and fixed in 7.2.4 with commit 1ab55354368d071ebaee4d8c82313955eab65a04
	Issue introduced in 6.18 with commit 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 and fixed in 7.3-rc1 with commit becf07e2b0053027495ecd671b1f82fb2e615f68

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-2026-80958
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/md/dm-pcache/cache_gc.c
	drivers/md/dm-pcache/cache_key.c
	drivers/md/dm-pcache/cache_writeback.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/2cd9776fe3f2d88ec22c36d3c8ba09fbf9d5500c
	https://git.kernel.org/stable/c/1ab55354368d071ebaee4d8c82313955eab65a04
	https://git.kernel.org/stable/c/becf07e2b0053027495ecd671b1f82fb2e615f68