CVE-2026-64213: hwmon: (lm90) Add lock protection to lm90_alert

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

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

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

hwmon: (lm90) Add lock protection to lm90_alert

Sashiko reports:

lm90_alert() executes in the smbus alert context and calls
lm90_update_confreg() to disable the hardware alert line, without
acquiring hwmon_lock.

Concurrently, sysfs write operations (such as lm90_write_convrate) hold
the hwmon_lock, temporarily modify data->config, and then restore it.

If an alert interrupt occurs concurrently with a sysfs write, the sysfs
path will overwrite the alert handler's modifications to data->config
and the hardware register.

This unintentionally re-enables the hardware alert line while the alarm is
still active, causing an interrupt storm.

Add the missing lock to lm90_alert() to solve the problem.

The Linux kernel CVE team has assigned CVE-2026-64213 to this issue.


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

	Issue introduced in 5.3 with commit 7a1d220ccb0cc2b808eb176fb05bf55a38179f3f and fixed in 6.18.34 with commit bed1fc32e0eb653806fa98afcf55f9a311fc4ce2
	Issue introduced in 5.3 with commit 7a1d220ccb0cc2b808eb176fb05bf55a38179f3f and fixed in 7.0.11 with commit b0b66aae8a94c3663d47e4000b0e81b89ce32186
	Issue introduced in 5.3 with commit 7a1d220ccb0cc2b808eb176fb05bf55a38179f3f and fixed in 7.1 with commit 873e919e3101063a7a75989510ccfc125a4391cf

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-2026-64213
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/lm90.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/bed1fc32e0eb653806fa98afcf55f9a311fc4ce2
	https://git.kernel.org/stable/c/b0b66aae8a94c3663d47e4000b0e81b89ce32186
	https://git.kernel.org/stable/c/873e919e3101063a7a75989510ccfc125a4391cf