CVE-2021-47393

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

hwmon: (mlxreg-fan) Return non-zero value when fan current state is enforced from sysfs

Fan speed minimum can be enforced from sysfs. For example, setting current fan speed to 20 is used to enforce fan speed to be at 100% speed, 19 - to be not below 90% speed, etcetera. This feature provides ability to limit fan speed according to some system wise considerations, like absence of some replaceable units or high system ambient temperature.

Request for changing fan minimum speed is configuration request and can be set only through 'sysfs' write procedure. In this situation value of argument 'state' is above nominal fan speed maximum.

Return non-zero code in this case to avoid thermal_cooling_device_stats_update() call, because in this case statistics update violates thermal statistics table range. The issues is observed in case kernel is configured with option CONFIG_THERMAL_STATISTICS.

Here is the trace from KASAN: [ 159.506659] BUG: KASAN: slab-out-of-bounds in thermal_cooling_device_stats_update+0x7d/0xb0 [ 159.516016] Read of size 4 at addr ffff888116163840 by task hw-management.s/7444 [ 159.545625] Call Trace: [ 159.548366] dump_stack+0x92/0xc1 [ 159.552084] ? thermal_cooling_device_stats_update+0x7d/0xb0 [ 159.635869] thermal_zone_device_update+0x345/0x780 [ 159.688711] thermal_zone_device_set_mode+0x7d/0xc0 [ 159.694174] mlxsw_thermal_modules_init+0x48f/0x590 [mlxsw_core] [ 159.700972] ? mlxsw_thermal_set_cur_state+0x5a0/0x5a0 [mlxsw_core] [ 159.731827] mlxsw_thermal_init+0x763/0x880 [mlxsw_core] [ 160.070233] RIP: 0033:0x7fd995909970 [ 160.074239] Code: 73 01 c3 48 8b 0d 28 d5 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 99 2d 2c 00 00 75 10 b8 01 00 00 00 0f 05 <48> 3d 01 f0 ff .. [ 160.095242] RSP: 002b:00007fff54f5d938 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 [ 160.103722] RAX: ffffffffffffffda RBX: 0000000000000013 RCX: 00007fd995909970 [...