Subject: CVE-2021-47441: mlxsw: thermal: Fix out-of-bounds memory accesses

From: Greg Kroah-Hartman <[email-masked]>

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/[email-masked]/
[3] https://lore.kernel.org/linux-pm/[email-masked]/

The Linux kernel CVE team has assigned CVE-2021-47441 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 4.10 with commit a50c1e35650b and fixed in 5.4.155 with commit ae0993739e14
	Issue introduced in 4.10 with commit a50c1e35650b and fixed in 5.10.75 with commit e59d839743b5
	Issue introduced in 4.10 with commit a50c1e35650b and fixed in 5.14.14 with commit df8e58716afb
	Issue introduced in 4.10 with commit a50c1e35650b and fixed in 5.15 with commit 332fdf951df8

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2021-47441
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/net/ethernet/mellanox/mlxsw/core_thermal.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/ae0993739e14a102d506aa09e11b0065f3144f10
	https://git.kernel.org/stable/c/e59d839743b50cb1d3f42a786bea48cc5621d254
	https://git.kernel.org/stable/c/df8e58716afb3bee2b59de66b1ba1033f2e26303
	https://git.kernel.org/stable/c/332fdf951df8b870e3da86b122ae304e2aabe88c