Subject: CVE-2021-47058: regmap: set debugfs_name to NULL after it is freed

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

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

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

regmap: set debugfs_name to NULL after it is freed

There is a upstream commit cffa4b2122f5("regmap:debugfs:
Fix a memory leak when calling regmap_attach_dev") that
adds a if condition when create name for debugfs_name.
With below function invoking logical, debugfs_name is
freed in regmap_debugfs_exit(), but it is not created again
because of the if condition introduced by above commit.
regmap_reinit_cache()
	regmap_debugfs_exit()
	...
	regmap_debugfs_init()
So, set debugfs_name to NULL after it is freed.

The Linux kernel CVE team has assigned CVE-2021-47058 to this issue.

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

	Issue introduced in 4.19.168 with commit 5b654b030079 and fixed in 4.19.191 with commit 2dc1554d5f0f
	Issue introduced in 5.4.90 with commit 480c5e9c7e4c and fixed in 5.4.119 with commit d8897f7b2283
	Issue introduced in 5.10.8 with commit c9698380b01a and fixed in 5.10.37 with commit eb949f891226
	Issue introduced in 5.11 with commit cffa4b2122f5 and fixed in 5.11.21 with commit c764e375ae64
	Issue introduced in 5.11 with commit cffa4b2122f5 and fixed in 5.12.4 with commit b9e569ae1da3
	Issue introduced in 5.11 with commit cffa4b2122f5 and fixed in 5.13 with commit e41a962f82e7

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-2021-47058
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/base/regmap/regmap-debugfs.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/2dc1554d5f0fdaf47cc5bea442b84b9226fea867
	https://git.kernel.org/stable/c/d8897f7b2283a500666c85ef06e820df38ed7b52
	https://git.kernel.org/stable/c/eb949f891226c012138ffd9df90d1e509f428ae6
	https://git.kernel.org/stable/c/c764e375ae647832de1ee73d43a4bb3ef8a8f43d
	https://git.kernel.org/stable/c/b9e569ae1da3a113b3acee8703c94777fd20938a
	https://git.kernel.org/stable/c/e41a962f82e7afb5b1ee644f48ad0b3aee656268