CVE-2026-74687: watchdog: at91sam9_wdt: prevent timer rearm during teardown

CVE-2026-74687: watchdog: at91sam9_wdt: prevent timer rearm during teardown

[Greg Kroah-Hartman]

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

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

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

watchdog: at91sam9_wdt: prevent timer rearm during teardown

at91_ping() rearms the watchdog timer from its callback. timer_delete()
neither waits for a running callback nor prevents it from rearming the
timer, so probe failure or driver removal can leave the timer accessing the
devm-allocated at91wdt after it has been freed.

Use timer_shutdown_sync() on both teardown paths. It waits for a running
callback and rejects any attempt by the callback to rearm the timer.

The Linux kernel CVE team has assigned CVE-2026-74687 to this issue.


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

	Issue introduced in 3.14 with commit 5161b31dc39a6d6dadc95f298de48a725b73ada8 and fixed in 6.18.45 with commit 29fe74c9aa69d78c1c6a3930f1d9fc5db71a6eed
	Issue introduced in 3.14 with commit 5161b31dc39a6d6dadc95f298de48a725b73ada8 and fixed in 7.1.9 with commit b7949b0a7d998013b7ec8617a0ef5b07cca80be4
	Issue introduced in 3.14 with commit 5161b31dc39a6d6dadc95f298de48a725b73ada8 and fixed in 7.2 with commit 8444d66aa6b6e7fe0a26fa1a00a11cb4d0523783

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-2026-74687
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/watchdog/at91sam9_wdt.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/29fe74c9aa69d78c1c6a3930f1d9fc5db71a6eed
	https://git.kernel.org/stable/c/b7949b0a7d998013b7ec8617a0ef5b07cca80be4
	https://git.kernel.org/stable/c/8444d66aa6b6e7fe0a26fa1a00a11cb4d0523783