CVE-2022-48942

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.

Weakness

The product dereferences a pointer that it expects to be valid but is NULL.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/1b5f517cca36292076d9e38fa6e33a257703e62e
• https://git.kernel.org/stable/c/7efe8499cb90651c540753f4269d2d43ede14223
• https://git.kernel.org/stable/c/8a1969e14ad93663f9a3ed02ccc2138da9956a0e
• https://git.kernel.org/stable/c/962b2a3188bfa5388756ffbc47dfa5ff59cb8011