| Description | In the Linux kernel, the following vulnerability has been resolved:
mlxsw: thermal: Fix out-of-bounds memory accesses
Currently, mlxsw allows cooling states to be set above the maximum
cooling state supported by the driver:
# cat /sys/class/thermal/thermal_zone2/cdev0/type
mlxsw_fan
# cat /sys/class/thermal/thermal_zone2/cdev0/max_state
10
# echo 18 > /sys/class/thermal/thermal_zone2/cdev0/cur_state
# echo $?
0
This results in out-of-bounds memory accesses when thermal state
transition statistics are enabled (CONFIG_THERMAL_STATISTICS=y), as the
transition table is accessed with a too large index (state) [1].
According to the thermal maintainer, it is the responsibility of the
driver to reject such operations [2].
Therefore, return an error when the state to be set exceeds the maximum
cooling state supported by the driver.
To avoid dead code, as suggested by the thermal maintainer [3],
partially revert commit a421ce088ac8 ("mlxsw: core: Extend cooling
device with cooling levels") that tried to interpret these invalid
cooling states (above the maximum) in a special way. The cooling levels
array is not removed in order to prevent the fans going below 20% PWM,
which would cause them to get stuck at 0% PWM.
[1]
BUG: KASAN: slab-out-of-bounds in thermal_cooling_device_stats_update+0x271/0x290
Read of size 4 at addr ffff8881052f7bf8 by task kworker/0:0/5
CPU: 0 PID: 5 Comm: kworker/0:0 Not tainted 5.15.0-rc3-custom-45935-gce1adf704b14 #122
Hardware name: Mellanox Technologies Ltd. "MSN2410-CB2FO"/"SA000874", BIOS 4.6.5 03/08/2016
Workqueue: events_freezable_power_ thermal_zone_device_check
Call Trace:
dump_stack_lvl+0x8b/0xb3
print_address_description.constprop.0+0x1f/0x140
kasan_report.cold+0x7f/0x11b
thermal_cooling_device_stats_update+0x271/0x290
__thermal_cdev_update+0x15e/0x4e0
thermal_cdev_update+0x9f/0xe0
step_wise_throttle+0x770/0xee0
thermal_zone_device_update+0x3f6/0xdf0
process_one_work+0xa42/0x1770
worker_thread+0x62f/0x13e0
kthread+0x3ee/0x4e0
ret_from_fork+0x1f/0x30
Allocated by task 1:
kasan_save_stack+0x1b/0x40
__kasan_kmalloc+0x7c/0x90
thermal_cooling_device_setup_sysfs+0x153/0x2c0
__thermal_cooling_device_register.part.0+0x25b/0x9c0
thermal_cooling_device_register+0xb3/0x100
mlxsw_thermal_init+0x5c5/0x7e0
__mlxsw_core_bus_device_register+0xcb3/0x19c0
mlxsw_core_bus_device_register+0x56/0xb0
mlxsw_pci_probe+0x54f/0x710
local_pci_probe+0xc6/0x170
pci_device_probe+0x2b2/0x4d0
really_probe+0x293/0xd10
__driver_probe_device+0x2af/0x440
driver_probe_device+0x51/0x1e0
__driver_attach+0x21b/0x530
bus_for_each_dev+0x14c/0x1d0
bus_add_driver+0x3ac/0x650
driver_register+0x241/0x3d0
mlxsw_sp_module_init+0xa2/0x174
do_one_initcall+0xee/0x5f0
kernel_init_freeable+0x45a/0x4de
kernel_init+0x1f/0x210
ret_from_fork+0x1f/0x30
The buggy address belongs to the object at ffff8881052f7800
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 1016 bytes inside of
1024-byte region [ffff8881052f7800, ffff8881052f7c00)
The buggy address belongs to the page:
page:0000000052355272 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1052f0
head:0000000052355272 order:3 compound_mapcount:0 compound_pincount:0
flags: 0x200000000010200(slab|head|node=0|zone=2)
raw: 0200000000010200 ffffea0005034800 0000000300000003 ffff888100041dc0
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff8881052f7a80: 00 00 00 00 00 00 04 fc fc fc fc fc fc fc fc fc
ffff8881052f7b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881052f7b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff8881052f7c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881052f7c80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[2] https://lore.kernel.org/linux-pm/9aca37cb-1629-5c67-
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