CVE-2026-72436: netfilter: ipset: Don't use test_bit() in lockless RCU readers in hash types

CVE-2026-72436: netfilter: ipset: Don't use test_bit() in lockless RCU readers in hash types

[Greg Kroah-Hartman]

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

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

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

netfilter: ipset: Don't use test_bit() in lockless RCU readers in hash types

Sashiko pointed out that there are a few lockless RCU readers
using test_bit() which is a relaxed atomic operation and
provides no memory barrier guarantees. Use test_bit_acquire()
instead where the operation may run parallel with add/del/gc,
i.e. is not one from the next cases

- protected by region lock
- in a set destroy phase
- in a new/temporary set creation phase

The Linux kernel CVE team has assigned CVE-2026-72436 to this issue.


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

	Issue introduced in 4.2 with commit 18f84d41d34fa35d0d64bbaea01fe664553ecc06 and fixed in 6.1.178 with commit c107233d2ff4fd7cef5d02f9124b99194957a710
	Issue introduced in 4.2 with commit 18f84d41d34fa35d0d64bbaea01fe664553ecc06 and fixed in 6.6.145 with commit 6329d3a9afe715fddda0460cfa46b496d61c2fe0
	Issue introduced in 4.2 with commit 18f84d41d34fa35d0d64bbaea01fe664553ecc06 and fixed in 6.12.97 with commit 7445fe965b7d8756070a40e80f8b73348ccda1d7
	Issue introduced in 4.2 with commit 18f84d41d34fa35d0d64bbaea01fe664553ecc06 and fixed in 6.18.40 with commit c4d257734e91bfcdc71d41843392dd6400b5bb1b
	Issue introduced in 4.2 with commit 18f84d41d34fa35d0d64bbaea01fe664553ecc06 and fixed in 7.1.5 with commit 3219d74e4536658c937fd878a327257b86ce80dd
	Issue introduced in 4.2 with commit 18f84d41d34fa35d0d64bbaea01fe664553ecc06 and fixed in 7.2-rc1 with commit e4b4984e28c16406ecb318444dea4a8bf47def3e

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-2026-72436
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:
	net/netfilter/ipset/ip_set_hash_gen.h


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/c107233d2ff4fd7cef5d02f9124b99194957a710
	https://git.kernel.org/stable/c/6329d3a9afe715fddda0460cfa46b496d61c2fe0
	https://git.kernel.org/stable/c/7445fe965b7d8756070a40e80f8b73348ccda1d7
	https://git.kernel.org/stable/c/c4d257734e91bfcdc71d41843392dd6400b5bb1b
	https://git.kernel.org/stable/c/3219d74e4536658c937fd878a327257b86ce80dd
	https://git.kernel.org/stable/c/e4b4984e28c16406ecb318444dea4a8bf47def3e