CVE-2026-72383: sctp: fix addr_wq_timer race in sctp_free_addr_wq()

CVE-2026-72383: sctp: fix addr_wq_timer race in sctp_free_addr_wq()

[Greg Kroah-Hartman]

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

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

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

sctp: fix addr_wq_timer race in sctp_free_addr_wq()

sctp_free_addr_wq() previously removed addr_wq_timer using timer_delete()
while holding addr_wq_lock. However, timer_delete() does not guarantee that
a currently running timer handler has completed.

This allows a race with sctp_addr_wq_timeout_handler(), where the handler
may still run after addr_waitq has been freed, acquire addr_wq_lock, and
access freed memory, leading to a use-after-free.

Fix this by calling timer_shutdown_sync() before taking addr_wq_lock.  This
guarantees that any in-flight timer handler has finished and prevents the
timer from being re-armed during teardown, making subsequent cleanup safe.

The Linux kernel CVE team has assigned CVE-2026-72383 to this issue.


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

	Issue introduced in 3.7 with commit 4db67e808640e3934d82ce61ee8e2e89fd877ba8 and fixed in 6.18.40 with commit a8323fb2ab6cd6978f359daeed6688e0cadf32ba
	Issue introduced in 3.7 with commit 4db67e808640e3934d82ce61ee8e2e89fd877ba8 and fixed in 7.1.5 with commit c3e5cac47519d77ad36b9c03a1df1536aaa0c4a1
	Issue introduced in 3.7 with commit 4db67e808640e3934d82ce61ee8e2e89fd877ba8 and fixed in 7.2-rc2 with commit 976c19de0f22a857ba0112f39635f8fd7a257568

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-2026-72383
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/sctp/protocol.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/a8323fb2ab6cd6978f359daeed6688e0cadf32ba
	https://git.kernel.org/stable/c/c3e5cac47519d77ad36b9c03a1df1536aaa0c4a1
	https://git.kernel.org/stable/c/976c19de0f22a857ba0112f39635f8fd7a257568