CVE-2026-74552: hwmon: (lm90) Only report alarms if driver is ready

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

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

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

hwmon: (lm90) Only report alarms if driver is ready

Userspace can read sysfs attributes before driver registration is complete,
immediately after devm_hwmon_device_register_with_info() has been called.
At that time, data->hwmon_dev is not yet initialized. This can trigger
a NULL pointer access since lm90_update_device() and with it
lm90_update_alarms_locked() will be called. This call schedules
report_work and lm90_report_alarms(), which passes the still-NULL
data->hwmon_dev to hwmon_notify_event() and triggers a NULL pointer
dereference.

Fix the problem by only scheduling the report and alert workers
data->hwmon_dev is set.

The Linux kernel CVE team has assigned CVE-2026-74552 to this issue.


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

	Issue introduced in 6.0 with commit f6d0775119fb905fb02eafa98d575cf8ee792d46 and fixed in 6.6.151 with commit 4eed33c7db5c0c573928d28d8a2c003642c679b8
	Issue introduced in 6.0 with commit f6d0775119fb905fb02eafa98d575cf8ee792d46 and fixed in 6.12.103 with commit 70d9a71aa407044d70b50d356b6decf6659c4d56
	Issue introduced in 6.0 with commit f6d0775119fb905fb02eafa98d575cf8ee792d46 and fixed in 6.18.44 with commit 075fce376cf852db9293481edce07c181a9b1f46
	Issue introduced in 6.0 with commit f6d0775119fb905fb02eafa98d575cf8ee792d46 and fixed in 7.1.8 with commit f0b791a006512a48b6348494cb6960598fa99a58
	Issue introduced in 6.0 with commit f6d0775119fb905fb02eafa98d575cf8ee792d46 and fixed in 7.2-rc6 with commit aa9429edf9fc0e90d6f4da19ea4b5495a54ab117

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-2026-74552
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/4eed33c7db5c0c573928d28d8a2c003642c679b8
	https://git.kernel.org/stable/c/70d9a71aa407044d70b50d356b6decf6659c4d56
	https://git.kernel.org/stable/c/075fce376cf852db9293481edce07c181a9b1f46
	https://git.kernel.org/stable/c/f0b791a006512a48b6348494cb6960598fa99a58
	https://git.kernel.org/stable/c/aa9429edf9fc0e90d6f4da19ea4b5495a54ab117