mlxsw: thermal: Fix out-of-bounds memory accesses

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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