linux-cve-announce - CVE-2025-40024: vhost: Take a reference on the task in struct vhost

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Message-ID: <2025102404-CVE-2025-40024-8739@gregkh>
Date: Fri, 24 Oct 2025 14:25:07 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40024: vhost: Take a reference on the task in struct vhost_task.

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

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

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

vhost: Take a reference on the task in struct vhost_task.

vhost_task_create() creates a task and keeps a reference to its
task_struct. That task may exit early via a signal and its task_struct
will be released.
A pending vhost_task_wake() will then attempt to wake the task and
access a task_struct which is no longer there.

Acquire a reference on the task_struct while creating the thread and
release the reference while the struct vhost_task itself is removed.
If the task exits early due to a signal, then the vhost_task_wake() will
still access a valid task_struct. The wake is safe and will be skipped
in this case.

The Linux kernel CVE team has assigned CVE-2025-40024 to this issue.

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

	Issue introduced in 6.4 with commit f9010dbdce911ee1f1af1398a24b1f9f992e0080 and fixed in 6.6.109 with commit 82a1463c968b1a6ae598a4f2fcef17b71bb7d3a0
	Issue introduced in 6.4 with commit f9010dbdce911ee1f1af1398a24b1f9f992e0080 and fixed in 6.12.50 with commit d2be773a92874a070215b51b730cb2b1eaa8fae2
	Issue introduced in 6.4 with commit f9010dbdce911ee1f1af1398a24b1f9f992e0080 and fixed in 6.16.10 with commit 7ce635b3d3aba43296b62b5a2d97c008bc51cbd2
	Issue introduced in 6.4 with commit f9010dbdce911ee1f1af1398a24b1f9f992e0080 and fixed in 6.17 with commit afe16653e05db07d658b55245c7a2e0603f136c0

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-2025-40024
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:
	kernel/vhost_task.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/82a1463c968b1a6ae598a4f2fcef17b71bb7d3a0
	https://git.kernel.org/stable/c/d2be773a92874a070215b51b730cb2b1eaa8fae2
	https://git.kernel.org/stable/c/7ce635b3d3aba43296b62b5a2d97c008bc51cbd2
	https://git.kernel.org/stable/c/afe16653e05db07d658b55245c7a2e0603f136c0