CVE-2026-72032: net/mlx5: HWS, fix matcher leak on resize target setup failure

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

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

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

net/mlx5: HWS, fix matcher leak on resize target setup failure

hws_bwc_matcher_move() allocates a replacement matcher before setting it
as the resize target. If mlx5hws_matcher_resize_set_target() fails, the
replacement matcher is not attached anywhere and is leaked.

Fix the leak by destroying the replacement matcher before returning from
the resize-target failure path.

The bug was first flagged by an experimental analysis tool we are
developing for kernel memory-management bugs while analyzing
v6.13-rc1. The tool is still under development and is not yet publicly
available. Manual inspection confirms that the bug is still
present in v7.1.1.

An x86_64 allyesconfig build showed no new warnings. As we do not have a
mlx5 HWS-capable device to test with, no runtime testing was able to be
performed.

The Linux kernel CVE team has assigned CVE-2026-72032 to this issue.


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

	Issue introduced in 6.12 with commit 2111bb970c787b16b002dc726c1d296ce87a00fb and fixed in 6.12.101 with commit a751ccdc6ea9bde154f25a5ba66926f462f96c19
	Issue introduced in 6.12 with commit 2111bb970c787b16b002dc726c1d296ce87a00fb and fixed in 6.18.40 with commit 1dce4f4bb3c1c02080b1a45bdd2abb2913a6642a
	Issue introduced in 6.12 with commit 2111bb970c787b16b002dc726c1d296ce87a00fb and fixed in 7.1.5 with commit ae0265f0a95aaacef59d560a3e1ea36db8be9a52
	Issue introduced in 6.12 with commit 2111bb970c787b16b002dc726c1d296ce87a00fb and fixed in 7.2-rc2 with commit bb09d0e64ecaa0aa0f7d1133a1696ed74dead295

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-2026-72032
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/net/ethernet/mellanox/mlx5/core/steering/hws/bwc.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/a751ccdc6ea9bde154f25a5ba66926f462f96c19
	https://git.kernel.org/stable/c/1dce4f4bb3c1c02080b1a45bdd2abb2913a6642a
	https://git.kernel.org/stable/c/ae0265f0a95aaacef59d560a3e1ea36db8be9a52
	https://git.kernel.org/stable/c/bb09d0e64ecaa0aa0f7d1133a1696ed74dead295