Subject: CVE-2021-47386: hwmon: (w83791d) Fix NULL pointer dereference by removing unnecessary structure field

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

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

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

hwmon: (w83791d) Fix NULL pointer dereference by removing unnecessary structure field

If driver read val value sufficient for
(val & 0x08) && (!(val & 0x80)) && ((val & 0x7) == ((val >> 4) & 0x7))
from device then Null pointer dereference occurs.
(It is possible if tmp = 0b0xyz1xyz, where same literals mean same numbers)
Also lm75[] does not serve a purpose anymore after switching to
devm_i2c_new_dummy_device() in w83791d_detect_subclients().

The patch fixes possible NULL pointer dereference by removing lm75[].

Found by Linux Driver Verification project (linuxtesting.org).

[groeck: Dropped unnecessary continuation lines, fixed multi-line alignment]

The Linux kernel CVE team has assigned CVE-2021-47386 to this issue.

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

	Fixed in 5.4.151 with commit 44d3c480e4e2
	Fixed in 5.10.71 with commit 516d90550390
	Fixed in 5.14.10 with commit 16887ae4e3de
	Fixed in 5.15 with commit 943c15ac1b84

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-2021-47386
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/hwmon/w83791d.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/44d3c480e4e2a75bf6296a18b4356157991ccd80
	https://git.kernel.org/stable/c/516d9055039017a20a698103be2b556b4c976bb8
	https://git.kernel.org/stable/c/16887ae4e3defd2c4e7913b6c539f33eaf4eac5c
	https://git.kernel.org/stable/c/943c15ac1b84d378da26bba41c83c67e16499ac4