linux-cve-announce - CVE-2025-40160: xen/events: Return -EEXIST for bound VIRQs

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Message-ID: <2025111239-CVE-2025-40160-b13a@gregkh>
Date: Wed, 12 Nov 2025 19:24:41 +0900
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40160: xen/events: Return -EEXIST for bound VIRQs

From: Greg Kroah-Hartman <gregkh@...nel.org>

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

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

xen/events: Return -EEXIST for bound VIRQs

Change find_virq() to return -EEXIST when a VIRQ is bound to a
different CPU than the one passed in.  With that, remove the BUG_ON()
from bind_virq_to_irq() to propogate the error upwards.

Some VIRQs are per-cpu, but others are per-domain or global.  Those must
be bound to CPU0 and can then migrate elsewhere.  The lookup for
per-domain and global will probably fail when migrated off CPU 0,
especially when the current CPU is tracked.  This now returns -EEXIST
instead of BUG_ON().

A second call to bind a per-domain or global VIRQ is not expected, but
make it non-fatal to avoid trying to look up the irq, since we don't
know which per_cpu(virq_to_irq) it will be in.

The Linux kernel CVE team has assigned CVE-2025-40160 to this issue.

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

	Fixed in 6.6.113 with commit 612ef6056855c0aacb9b25d1d853c435754483f7
	Fixed in 6.12.54 with commit a1e7f07ae6b594f1ba5be46c6125b43bc505c5aa
	Fixed in 6.17.4 with commit f81db055a793eca9d05f79658ff62adafb41d664
	Fixed in 6.18-rc1 with commit 07ce121d93a5e5fb2440a24da3dbf408fcee978e

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-2025-40160
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/events/events_base.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/612ef6056855c0aacb9b25d1d853c435754483f7
	https://git.kernel.org/stable/c/a1e7f07ae6b594f1ba5be46c6125b43bc505c5aa
	https://git.kernel.org/stable/c/f81db055a793eca9d05f79658ff62adafb41d664
	https://git.kernel.org/stable/c/07ce121d93a5e5fb2440a24da3dbf408fcee978e