Subject: CVE-2021-46979: iio: core: fix ioctl handlers removal

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

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

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

iio: core: fix ioctl handlers removal

Currently ioctl handlers are removed twice. For the first time during
iio_device_unregister() then later on inside
iio_device_unregister_eventset() and iio_buffers_free_sysfs_and_mask().
Double free leads to kernel panic.

Fix this by not touching ioctl handlers list directly but rather
letting code responsible for registration call the matching cleanup
routine itself.

The Linux kernel CVE team has assigned CVE-2021-46979 to this issue.

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

	Issue introduced in 5.11 with commit 8dedcc3eee3a and fixed in 5.11.22 with commit 11e1cae5da40
	Issue introduced in 5.11 with commit 8dedcc3eee3a and fixed in 5.12.5 with commit ab6c935ba3a0
	Issue introduced in 5.11 with commit 8dedcc3eee3a and fixed in 5.13 with commit 901f84de0e16

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-2021-46979
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/iio/industrialio-core.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/11e1cae5da4096552f7c091476cbadbc0d1817da
	https://git.kernel.org/stable/c/ab6c935ba3a04317632f3b8b68675bdbaf395303
	https://git.kernel.org/stable/c/901f84de0e16bde10a72d7eb2f2eb73fcde8fa1a