CVE-2026-72104: dm-pcache: reject option groups without values

From: Greg Kroah-Hartman <[email protected]>

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

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

dm-pcache: reject option groups without values

The pcache target parses optional arguments as name/value pairs.  A
table that advertises one optional argument and supplies only a
recognized option name, for example "cache_mode", reaches
parse_cache_opts() with argc == 1.  The parser consumes the name,
decrements argc to zero, then calls dm_shift_arg() again for the value.
dm_shift_arg() returns NULL when no arguments remain, and the following
strcmp() dereferences that NULL pointer.

Check that each recognized option has a value before consuming it.  This
keeps valid "cache_mode writeback" and "data_crc true/false" tables
unchanged while making malformed tables fail during target construction
with a precise missing-value error.

The Linux kernel CVE team has assigned CVE-2026-72104 to this issue.


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

	Issue introduced in 6.18 with commit 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 and fixed in 6.18.40 with commit 1247615aadb74c89c1b2f01a6de7df9dab92ecb3
	Issue introduced in 6.18 with commit 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 and fixed in 7.1.5 with commit 0cbe13fe540330d31e5273bbf8cbd66bc7c9cb5a
	Issue introduced in 6.18 with commit 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 and fixed in 7.2-rc3 with commit d9c631e3fbd44246a2be781d26cfacbb9b8ec127

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-2026-72104
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/dm_pcache.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/1247615aadb74c89c1b2f01a6de7df9dab92ecb3
	https://git.kernel.org/stable/c/0cbe13fe540330d31e5273bbf8cbd66bc7c9cb5a
	https://git.kernel.org/stable/c/d9c631e3fbd44246a2be781d26cfacbb9b8ec127