Subject: CVE-2024-44937: platform/x86: intel-vbtn: Protect ACPI notify handler against recursion

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

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

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

platform/x86: intel-vbtn: Protect ACPI notify handler against recursion

Since commit e2ffcda16290 ("ACPI: OSL: Allow Notify () handlers to run on
all CPUs") ACPI notify handlers like the intel-vbtn notify_handler() may
run on multiple CPU cores racing with themselves.

This race gets hit on Dell Venue 7140 tablets when undocking from
the keyboard, causing the handler to try and register priv->switches_dev
twice, as can be seen from the dev_info() message getting logged twice:

[ 83.861800] intel-vbtn INT33D6:00: Registering Intel Virtual Switches input-dev after receiving a switch event
[ 83.861858] input: Intel Virtual Switches as /devices/pci0000:00/0000:00:1f.0/PNP0C09:00/INT33D6:00/input/input17
[ 83.861865] intel-vbtn INT33D6:00: Registering Intel Virtual Switches input-dev after receiving a switch event

After which things go seriously wrong:
[ 83.861872] sysfs: cannot create duplicate filename '/devices/pci0000:00/0000:00:1f.0/PNP0C09:00/INT33D6:00/input/input17'
...
[ 83.861967] kobject: kobject_add_internal failed for input17 with -EEXIST, don't try to register things with the same name in the same directory.
[ 83.877338] BUG: kernel NULL pointer dereference, address: 0000000000000018
...

Protect intel-vbtn notify_handler() from racing with itself with a mutex
to fix this.

The Linux kernel CVE team has assigned CVE-2024-44937 to this issue.

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

	Issue introduced in 6.8 with commit e2ffcda16290 and fixed in 6.10.5 with commit 5c9618a3b6ea
	Issue introduced in 6.8 with commit e2ffcda16290 and fixed in 6.11 with commit e075c3b13a0a

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-2024-44937
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/platform/x86/intel/vbtn.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/5c9618a3b6ea94cf7bdff7702aca8bf2d777d97b
	https://git.kernel.org/stable/c/e075c3b13a0a142dcd3151b25d29a24f31b7b640