CVE-2026-74401: dlm: fix add msg handle in send_queue ordered

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

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

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

dlm: fix add msg handle in send_queue ordered

In a benchmark scenario triggering a lot of requests that triggers a lot
of DLM messages on the network it can be that the mh->seq is not ordered
according the oldest seq number. This ordering is required by
dlm_receive_ack as "before(mh->seq, seq)" will stop to check for older
sequence numbers that are ordered in the tail of "node->send_queue".

The side effects of not having it correct ordered regarding
"before(mh->seq, seq)" are refcounting issues and use-after free.

I only was able to reproduce this issue in a experimental DLM branch
and a user space DLM benchmark that uses io_uring. After changing this I
don't experienced any refcounting with the sending buffer issues anymore.

The Linux kernel CVE team has assigned CVE-2026-74401 to this issue.


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

	Issue introduced in 5.14 with commit 489d8e559c6596eb08e16447d9830bc39afbe54e and fixed in 6.6.145 with commit ae9e534e502a0f48c12baf83608c5de0ff0eab11
	Issue introduced in 5.14 with commit 489d8e559c6596eb08e16447d9830bc39afbe54e and fixed in 6.12.97 with commit 6369619f1b665f12d8c99cc6ff733c64eb08b22e
	Issue introduced in 5.14 with commit 489d8e559c6596eb08e16447d9830bc39afbe54e and fixed in 6.18.40 with commit 712714f818d83373847874ab0f8e426be79296cf
	Issue introduced in 5.14 with commit 489d8e559c6596eb08e16447d9830bc39afbe54e and fixed in 7.1.5 with commit 4d45250b1d22960f86d83245be188b16e456218b
	Issue introduced in 5.14 with commit 489d8e559c6596eb08e16447d9830bc39afbe54e and fixed in 7.2-rc1 with commit d2248cb70c070f8f04762872772e155b59016f17

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-2026-74401
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:
	fs/dlm/midcomms.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/ae9e534e502a0f48c12baf83608c5de0ff0eab11
	https://git.kernel.org/stable/c/6369619f1b665f12d8c99cc6ff733c64eb08b22e
	https://git.kernel.org/stable/c/712714f818d83373847874ab0f8e426be79296cf
	https://git.kernel.org/stable/c/4d45250b1d22960f86d83245be188b16e456218b
	https://git.kernel.org/stable/c/d2248cb70c070f8f04762872772e155b59016f17