CVE-2026-89573: dm array: reject an array block whose value size is not the caller's

CVE-2026-89573: dm array: reject an array block whose value size is not the caller's

[Greg Kroah-Hartman]

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

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

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

dm array: reject an array block whose value size is not the caller's

array_block_check() can only compare the header against itself, so a block
with value_size 4 and max_entries 1018 is internally consistent and passes.
dm-cache keeps two arrays -- mappings at 8 bytes and hints at 4 -- and the
roots for both live in the superblock. Point the mappings root at a hint
block and __load_mappings() walks it through an info whose value size is 8,
so element_at() strides 8 bytes over 4-byte entries and reaches offset 8160
of a 4096-byte block.

get_ablock() and __shadow_ablock() are the two places that hold the block
and the caller at once. Reject there when the two value sizes disagree.
Arrays only ever read their own blocks, so this fires on crafted metadata
only.

The Linux kernel CVE team has assigned CVE-2026-89573 to this issue.


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

	Issue introduced in 3.9 with commit 6513c29f44f2cc970c0e9fecfe5a6526c3e73025 and fixed in 6.12.109 with commit 7bf4b5cb42a4e27f36bcbc6209d82a5da9c0168c
	Issue introduced in 3.9 with commit 6513c29f44f2cc970c0e9fecfe5a6526c3e73025 and fixed in 6.18.50 with commit ac4a5eb8b002a0742c938fc98b922e243f53573a
	Issue introduced in 3.9 with commit 6513c29f44f2cc970c0e9fecfe5a6526c3e73025 and fixed in 7.2.4 with commit cb409b38b0232ee4385ef55cddcd6fbdd011a8a2
	Issue introduced in 3.9 with commit 6513c29f44f2cc970c0e9fecfe5a6526c3e73025 and fixed in 7.3-rc1 with commit 4538a287bdf5d0f9a379c678e5262b9f5783f547

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-2026-89573
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/persistent-data/dm-array.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/7bf4b5cb42a4e27f36bcbc6209d82a5da9c0168c
	https://git.kernel.org/stable/c/ac4a5eb8b002a0742c938fc98b922e243f53573a
	https://git.kernel.org/stable/c/cb409b38b0232ee4385ef55cddcd6fbdd011a8a2
	https://git.kernel.org/stable/c/4538a287bdf5d0f9a379c678e5262b9f5783f547