CVE-2024-36961

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

thermal/debugfs: Fix two locking issues with thermal zone debug

With the current thermal zone locking arrangement in the debugfs code,

user space can open the "mitigations" file for a thermal zone before

the zone's debugfs pointer is set which will result in a NULL pointer

dereference in tze_seq_start().

Moreover, thermal_debug_tz_remove() is not called under the thermal

zone lock, so it can run in parallel with the other functions accessing

the thermal zone's struct thermal_debugfs object. Then, it may clear

tz->debugfs after one of those functions has checked it and the

struct thermal_debugfs object may be freed prematurely.

To address the first problem, pass a pointer to the thermal zone's

struct thermal_debugfs object to debugfs_create_file() in

thermal_debug_tz_add() and make tze_seq_start(), tze_seq_next(),

tze_seq_stop(), and tze_seq_show() retrieve it from s->private

instead of a pointer to the thermal zone object. This will ensure

that tz_debugfs will be valid across the "mitigations" file accesses

until thermal_debugfs_remove_id() called by thermal_debug_tz_remove()

removes that file.

To address the second problem, use tz->lock in thermal_debug_tz_remove()

around the tz->debugfs value check (in case the same thermal zone is

removed at the same time in two different threads) and its reset to NULL.

Cc :6.8+ <[email protected]> # 6.8+