CVE-2026-80962: dm-pcache: validate geometry fields from on-disk cache_info

CVE-2026-80962: dm-pcache: validate geometry fields from on-disk cache_info

[Greg Kroah-Hartman]

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

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

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

dm-pcache: validate geometry fields from on-disk cache_info

cache_segs_init() iterates cache_info->n_segs times indexing
cache->segments[], which is sized to the cache device geometry, and
get_seg_id() takes each segment id from the on-media cache_info and the
per-segment next_seg link. Both come from cache device metadata that is
only CRC-protected with a fixed public seed, so whoever supplies the
cache device on a table load (CAP_SYS_ADMIN) controls them: an oversized
n_segs or an out-of-range id drives an out-of-bounds access of
cache->segments[] and a wild CACHE_DEV_SEGMENT() pointer into the device
mapping -- an out-of-bounds read and write from on-disk data.

Reject an n_segs that exceeds the device segment count and a segment id
that is out of range before either is used. Valid metadata is unaffected.

The Linux kernel CVE team has assigned CVE-2026-80962 to this issue.


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

	Issue introduced in 6.18 with commit 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 and fixed in 6.18.50 with commit ab5dcde6fa96bc115b85f3621c60e39c66229a90
	Issue introduced in 6.18 with commit 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 and fixed in 7.2.4 with commit 3e19172089ec81132a8a48e802b1034a744209f4
	Issue introduced in 6.18 with commit 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 and fixed in 7.3-rc1 with commit 32d1809da31094ef76fd98dc1f1a8b55ca1295dd

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-2026-80962
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.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/ab5dcde6fa96bc115b85f3621c60e39c66229a90
	https://git.kernel.org/stable/c/3e19172089ec81132a8a48e802b1034a744209f4
	https://git.kernel.org/stable/c/32d1809da31094ef76fd98dc1f1a8b55ca1295dd