linux-cve-announce - CVE-2025-21972: net: mctp: unshare packets when reassembling

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Message-ID: <2025040146-CVE-2025-21972-1415@gregkh>
Date: Tue,  1 Apr 2025 16:45:57 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21972: net: mctp: unshare packets when reassembling

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

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

net: mctp: unshare packets when reassembling

Ensure that the frag_list used for reassembly isn't shared with other
packets. This avoids incorrect reassembly when packets are cloned, and
prevents a memory leak due to circular references between fragments and
their skb_shared_info.

The upcoming MCTP-over-USB driver uses skb_clone which can trigger the
problem - other MCTP drivers don't share SKBs.

A kunit test is added to reproduce the issue.

The Linux kernel CVE team has assigned CVE-2025-21972 to this issue.


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

	Issue introduced in 5.15 with commit 4a992bbd365094730a31bae1e12a6ca695336d57 and fixed in 6.12.20 with commit 5c47d5bfa7b096cf8890afac32141c578583f8e0
	Issue introduced in 5.15 with commit 4a992bbd365094730a31bae1e12a6ca695336d57 and fixed in 6.13.8 with commit f44fff3d3c6cd67b6f348b821d73c4d6888c7a6e
	Issue introduced in 5.15 with commit 4a992bbd365094730a31bae1e12a6ca695336d57 and fixed in 6.14 with commit f5d83cf0eeb90fade4d5c4d17d24b8bee9ceeecc

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-2025-21972
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:
	net/mctp/route.c
	net/mctp/test/route-test.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/5c47d5bfa7b096cf8890afac32141c578583f8e0
	https://git.kernel.org/stable/c/f44fff3d3c6cd67b6f348b821d73c4d6888c7a6e
	https://git.kernel.org/stable/c/f5d83cf0eeb90fade4d5c4d17d24b8bee9ceeecc