CVE-2026-74546: hwmon: (adt7470) Fix divide-by-zero TOCTOU crash in fan speed read

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

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

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

hwmon: (adt7470) Fix divide-by-zero TOCTOU crash in fan speed read

If the fan data becomes 0 between the FAN_DATA_VALID() check and the
FAN_PERIOD_TO_RPM() conversion, it will result in a divide-by-zero crash
due to a race with a concurrent update of the cached fan value.

Fix a TOCTOU issue by reading fan data once.

The Linux kernel CVE team has assigned CVE-2026-74546 to this issue.


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

	Issue introduced in 5.15 with commit fc958a61ff6d34a0ec42744d3ff524ee202b2e9f and fixed in 6.6.151 with commit d328175045176f85c15c369bd21dc551351e7935
	Issue introduced in 5.15 with commit fc958a61ff6d34a0ec42744d3ff524ee202b2e9f and fixed in 6.12.103 with commit 832069bec79cf6f903441c5769d3cdba95d0af33
	Issue introduced in 5.15 with commit fc958a61ff6d34a0ec42744d3ff524ee202b2e9f and fixed in 6.18.44 with commit 96ad57d31763559d376416cdf3bf5ae79bbbebec
	Issue introduced in 5.15 with commit fc958a61ff6d34a0ec42744d3ff524ee202b2e9f and fixed in 7.1.8 with commit 76963b04b2d1c648d69949d8dd521e1ff7f40b51
	Issue introduced in 5.15 with commit fc958a61ff6d34a0ec42744d3ff524ee202b2e9f and fixed in 7.2-rc6 with commit 1b46fe9dc8f8de59310f37e6c5e5c0e05ded46c3

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-2026-74546
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/hwmon/adt7470.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/d328175045176f85c15c369bd21dc551351e7935
	https://git.kernel.org/stable/c/832069bec79cf6f903441c5769d3cdba95d0af33
	https://git.kernel.org/stable/c/96ad57d31763559d376416cdf3bf5ae79bbbebec
	https://git.kernel.org/stable/c/76963b04b2d1c648d69949d8dd521e1ff7f40b51
	https://git.kernel.org/stable/c/1b46fe9dc8f8de59310f37e6c5e5c0e05ded46c3