Subject: CVE-2022-48942: hwmon: Handle failure to register sensor with thermal zone correctly

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

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

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

hwmon: Handle failure to register sensor with thermal zone correctly

If an attempt is made to a sensor with a thermal zone and it fails,
the call to devm_thermal_zone_of_sensor_register() may return -ENODEV.
This may result in crashes similar to the following.

Unable to handle kernel NULL pointer dereference at virtual address 00000000000003cd
...
Internal error: Oops: 96000021 [#1] PREEMPT SMP
...
pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : mutex_lock+0x18/0x60
lr : thermal_zone_device_update+0x40/0x2e0
sp : ffff800014c4fc60
x29: ffff800014c4fc60 x28: ffff365ee3f6e000 x27: ffffdde218426790
x26: ffff365ee3f6e000 x25: 0000000000000000 x24: ffff365ee3f6e000
x23: ffffdde218426870 x22: ffff365ee3f6e000 x21: 00000000000003cd
x20: ffff365ee8bf3308 x19: ffffffffffffffed x18: 0000000000000000
x17: ffffdde21842689c x16: ffffdde1cb7a0b7c x15: 0000000000000040
x14: ffffdde21a4889a0 x13: 0000000000000228 x12: 0000000000000000
x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
x8 : 0000000001120000 x7 : 0000000000000001 x6 : 0000000000000000
x5 : 0068000878e20f07 x4 : 0000000000000000 x3 : 00000000000003cd
x2 : ffff365ee3f6e000 x1 : 0000000000000000 x0 : 00000000000003cd
Call trace:
 mutex_lock+0x18/0x60
 hwmon_notify_event+0xfc/0x110
 0xffffdde1cb7a0a90
 0xffffdde1cb7a0b7c
 irq_thread_fn+0x2c/0xa0
 irq_thread+0x134/0x240
 kthread+0x178/0x190
 ret_from_fork+0x10/0x20
Code: d503201f d503201f d2800001 aa0103e4 (c8e47c02)

Jon Hunter reports that the exact call sequence is:

hwmon_notify_event()
  --> hwmon_thermal_notify()
    --> thermal_zone_device_update()
      --> update_temperature()
        --> mutex_lock()

The hwmon core needs to handle all errors returned from calls
to devm_thermal_zone_of_sensor_register(). If the call fails
with -ENODEV, report that the sensor was not attached to a
thermal zone  but continue to register the hwmon device.

The Linux kernel CVE team has assigned CVE-2022-48942 to this issue.

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

	Issue introduced in 5.8 with commit 1597b374af22 and fixed in 5.10.103 with commit 962b2a3188bf
	Issue introduced in 5.8 with commit 1597b374af22 and fixed in 5.15.26 with commit 7efe8499cb90
	Issue introduced in 5.8 with commit 1597b374af22 and fixed in 5.16.12 with commit 8a1969e14ad9
	Issue introduced in 5.8 with commit 1597b374af22 and fixed in 5.17 with commit 1b5f517cca36

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-2022-48942
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/hwmon.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/962b2a3188bfa5388756ffbc47dfa5ff59cb8011
	https://git.kernel.org/stable/c/7efe8499cb90651c540753f4269d2d43ede14223
	https://git.kernel.org/stable/c/8a1969e14ad93663f9a3ed02ccc2138da9956a0e
	https://git.kernel.org/stable/c/1b5f517cca36292076d9e38fa6e33a257703e62e