CVE-2021-47202: thermal: Fix NULL pointer dereferences in of_thermal_ functions

CVE-2021-47202: thermal: Fix NULL pointer dereferences in of_thermal_ functions

[Greg Kroah-Hartman]

Description
===========

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

thermal: Fix NULL pointer dereferences in of_thermal_ functions

of_parse_thermal_zones() parses the thermal-zones node and registers a
thermal_zone device for each subnode. However, if a thermal zone is
consuming a thermal sensor and that thermal sensor device hasn't probed
yet, an attempt to set trip_point_*_temp for that thermal zone device
can cause a NULL pointer dereference. Fix it.

 console:/sys/class/thermal/thermal_zone87 # echo 120000 > trip_point_0_temp
 ...
 Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020
 ...
 Call trace:
  of_thermal_set_trip_temp+0x40/0xc4
  trip_point_temp_store+0xc0/0x1dc
  dev_attr_store+0x38/0x88
  sysfs_kf_write+0x64/0xc0
  kernfs_fop_write_iter+0x108/0x1d0
  vfs_write+0x2f4/0x368
  ksys_write+0x7c/0xec
  __arm64_sys_write+0x20/0x30
  el0_svc_common.llvm.7279915941325364641+0xbc/0x1bc
  do_el0_svc+0x28/0xa0
  el0_svc+0x14/0x24
  el0_sync_handler+0x88/0xec
  el0_sync+0x1c0/0x200

While at it, fix the possible NULL pointer dereference in other
functions as well: of_thermal_get_temp(), of_thermal_set_emul_temp(),
of_thermal_get_trend().

The Linux kernel CVE team has assigned CVE-2021-47202 to this issue.


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

	Fixed in 5.4.210 with commit 828f4c31684d
	Fixed in 5.10.81 with commit 6a315471cb6a
	Fixed in 5.14.21 with commit 0750f769b958
	Fixed in 5.15.4 with commit ef2590a5305e
	Fixed in 5.16 with commit 96cfe05051fd

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-2021-47202
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/thermal/thermal_of.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/828f4c31684da94ecf0b44a2cbd35bbede04f0bd
	https://git.kernel.org/stable/c/6a315471cb6a07f651e1d3adc8962730f4fcccac
	https://git.kernel.org/stable/c/0750f769b95841b34a9fe8c418dd792ff526bf86
	https://git.kernel.org/stable/c/ef2590a5305e0b8e9342f84c2214aa478ee7f28e
	https://git.kernel.org/stable/c/96cfe05051fd8543cdedd6807ec59a0e6c409195