Subject: CVE-2024-27067: xen/evtchn: avoid WARN() when unbinding an event channel

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

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

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

xen/evtchn: avoid WARN() when unbinding an event channel

When unbinding a user event channel, the related handler might be
called a last time in case the kernel was built with
CONFIG_DEBUG_SHIRQ. This might cause a WARN() in the handler.

Avoid that by adding an "unbinding" flag to struct user_event which
will short circuit the handler.

The Linux kernel CVE team has assigned CVE-2024-27067 to this issue.

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

	Issue introduced in 6.6.19 with commit 3c8f5965a993 and fixed in 6.6.23 with commit 99e425032c6e
	Issue introduced in 6.7 with commit 9e90e58c11b7 and fixed in 6.7.11 with commit 35485dad6e28
	Issue introduced in 6.7 with commit 9e90e58c11b7 and fixed in 6.8.2 with commit 9e2d4b58c1da
	Issue introduced in 6.7 with commit 9e90e58c11b7 and fixed in 6.9 with commit 51c23bd691c0

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-2024-27067
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/xen/evtchn.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/99e425032c6ec13584d3cd33846e0c7307501b47
	https://git.kernel.org/stable/c/35485dad6e28f9b17884764d4692b1655cb848d0
	https://git.kernel.org/stable/c/9e2d4b58c1da48a32905802aaeadba7084b46895
	https://git.kernel.org/stable/c/51c23bd691c0f1fb95b29731c356c6fd69925d17