CVE-2026-80957: dm-pcache: detect a cycle in the last-kset chain during replay

CVE-2026-80957: dm-pcache: detect a cycle in the last-kset chain during replay

[Greg Kroah-Hartman]

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

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

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

dm-pcache: detect a cycle in the last-kset chain during replay

cache_replay() follows the on-media last-kset chain by next_cache_seg_id
with no cond_resched(). A forged chain that points back into a segment it
has already visited makes the replay loop follow it forever.

Cap the last-kset hops at cache->n_segs; a valid chain visits each segment
at most once.

The Linux kernel CVE team has assigned CVE-2026-80957 to this issue.


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

	Issue introduced in 6.18 with commit 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 and fixed in 6.18.50 with commit 663ee2f3824a505b983162de44134e789f8230da
	Issue introduced in 6.18 with commit 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 and fixed in 7.2.4 with commit 5311dfc5cd70edccd110257e3f30b2c1dcd3768d
	Issue introduced in 6.18 with commit 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 and fixed in 7.3-rc1 with commit 16c3b3a326e70f246a605b3dc27b7f83ba4743e3

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-2026-80957
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_key.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/663ee2f3824a505b983162de44134e789f8230da
	https://git.kernel.org/stable/c/5311dfc5cd70edccd110257e3f30b2c1dcd3768d
	https://git.kernel.org/stable/c/16c3b3a326e70f246a605b3dc27b7f83ba4743e3