linux-cve-announce - CVE-2025-39976: futex: Use correct exit on failure from futex_hash_allocate

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Message-ID: <2025101558-CVE-2025-39976-59ea@gregkh>
Date: Wed, 15 Oct 2025 09:57:04 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-39976: futex: Use correct exit on failure from futex_hash_allocate_default()

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

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

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

futex: Use correct exit on failure from futex_hash_allocate_default()

copy_process() uses the wrong error exit path from futex_hash_allocate_default().
After exiting from futex_hash_allocate_default(), neither tasklist_lock
nor siglock has been acquired. The exit label bad_fork_core_free unlocks
both of these locks which is wrong.

The next exit label, bad_fork_cancel_cgroup, is the correct exit.
sched_cgroup_fork() did not allocate any resources that need to freed.

Use bad_fork_cancel_cgroup on error exit from futex_hash_allocate_default().

The Linux kernel CVE team has assigned CVE-2025-39976 to this issue.


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

	Issue introduced in 6.16 with commit 7c4f75a21f636486d2969d9b6680403ea8483539 and fixed in 6.16.10 with commit f1635765cd0fdbf27b04d9a50be91a01b5adda13
	Issue introduced in 6.16 with commit 7c4f75a21f636486d2969d9b6680403ea8483539 and fixed in 6.17 with commit 4ec3c15462b9f44562f45723a92e2807746ba7d1

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-2025-39976
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/fork.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/f1635765cd0fdbf27b04d9a50be91a01b5adda13
	https://git.kernel.org/stable/c/4ec3c15462b9f44562f45723a92e2807746ba7d1