linux-cve-announce - CVE-2025-21686: io_uring/rsrc: require cloned buffers to share accounting contexts

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Message-ID: <2025021054-CVE-2025-21686-d416@gregkh>
Date: Mon, 10 Feb 2025 16:58:54 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21686: io_uring/rsrc: require cloned buffers to share accounting contexts

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

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

io_uring/rsrc: require cloned buffers to share accounting contexts

When IORING_REGISTER_CLONE_BUFFERS is used to clone buffers from uring
instance A to uring instance B, where A and B use different MMs for
accounting, the accounting can go wrong:
If uring instance A is closed before uring instance B, the pinned memory
counters for uring instance B will be decremented, even though the pinned
memory was originally accounted through uring instance A; so the MM of
uring instance B can end up with negative locked memory.

The Linux kernel CVE team has assigned CVE-2025-21686 to this issue.


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

	Issue introduced in 6.12 with commit 7cc2a6eadcd7a5aa36ac63e6659f5c6138c7f4d2 and fixed in 6.12.12 with commit efd96fbe23fa87de39116f632401f67b93be21ab
	Issue introduced in 6.12 with commit 7cc2a6eadcd7a5aa36ac63e6659f5c6138c7f4d2 and fixed in 6.13.1 with commit cafc60ae35f82ebf156b3245f979ca61cbb8e42c
	Issue introduced in 6.12 with commit 7cc2a6eadcd7a5aa36ac63e6659f5c6138c7f4d2 and fixed in 6.14-rc1 with commit 19d340a2988d4f3e673cded9dde405d727d7e248

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-2025-21686
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:
	io_uring/rsrc.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/efd96fbe23fa87de39116f632401f67b93be21ab
	https://git.kernel.org/stable/c/cafc60ae35f82ebf156b3245f979ca61cbb8e42c
	https://git.kernel.org/stable/c/19d340a2988d4f3e673cded9dde405d727d7e248