CVE-2026-68356: watchdog: airoha: Prevent division by zero when clock frequency is zero

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

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

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

watchdog: airoha: Prevent division by zero when clock frequency is zero

clk_get_rate() can return 0 when the clock provider is not properly
configured or the clock is unmanaged. The driver uses wdt_freq as a
divisor directly in airoha_wdt_probe() to compute max_timeout and in
airoha_wdt_get_timeleft() to compute the remaining time, which results
in a division by zero.

Add a check for wdt_freq == 0 in probe and return -EINVAL with
dev_err_probe() to prevent the division by zero and provide a
diagnostic message.

The Linux kernel CVE team has assigned CVE-2026-68356 to this issue.


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

	Issue introduced in 6.13 with commit 3cf67f3769b8227ca75ca7102180a2e270ee01aa and fixed in 6.18.42 with commit 8681e5addf7171602616e256a09057697dcc75ca
	Issue introduced in 6.13 with commit 3cf67f3769b8227ca75ca7102180a2e270ee01aa and fixed in 7.1.6 with commit 57c3f5bd5be008cd5b4ff6a45b7cb90f5ca45a37
	Issue introduced in 6.13 with commit 3cf67f3769b8227ca75ca7102180a2e270ee01aa and fixed in 7.2-rc5 with commit bcfcd7619f277842430d197556463b401b839ee9

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-2026-68356
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/airoha_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/8681e5addf7171602616e256a09057697dcc75ca
	https://git.kernel.org/stable/c/57c3f5bd5be008cd5b4ff6a45b7cb90f5ca45a37
	https://git.kernel.org/stable/c/bcfcd7619f277842430d197556463b401b839ee9