linux-cve-announce - CVE-2023-54176: mptcp: stricter state check in mptcp

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Message-ID: <2025123022-CVE-2023-54176-efc2@gregkh>
Date: Tue, 30 Dec 2025 13:09:44 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-54176: mptcp: stricter state check in mptcp_worker

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

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

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

mptcp: stricter state check in mptcp_worker

As reported by Christoph, the mptcp protocol can run the
worker when the relevant msk socket is in an unexpected state:

connect()
// incoming reset + fastclose
// the mptcp worker is scheduled
mptcp_disconnect()
// msk is now CLOSED
listen()
mptcp_worker()

Leading to the following splat:

divide error: 0000 [#1] PREEMPT SMP
CPU: 1 PID: 21 Comm: kworker/1:0 Not tainted 6.3.0-rc1-gde5e8fd0123c #11
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014
Workqueue: events mptcp_worker
RIP: 0010:__tcp_select_window+0x22c/0x4b0 net/ipv4/tcp_output.c:3018
RSP: 0018:ffffc900000b3c98 EFLAGS: 00010293
RAX: 000000000000ffd7 RBX: 000000000000ffd7 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8214ce97 RDI: 0000000000000004
RBP: 000000000000ffd7 R08: 0000000000000004 R09: 0000000000010000
R10: 000000000000ffd7 R11: ffff888005afa148 R12: 000000000000ffd7
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88803ed00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000405270 CR3: 000000003011e006 CR4: 0000000000370ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 tcp_select_window net/ipv4/tcp_output.c:262 [inline]
 __tcp_transmit_skb+0x356/0x1280 net/ipv4/tcp_output.c:1345
 tcp_transmit_skb net/ipv4/tcp_output.c:1417 [inline]
 tcp_send_active_reset+0x13e/0x320 net/ipv4/tcp_output.c:3459
 mptcp_check_fastclose net/mptcp/protocol.c:2530 [inline]
 mptcp_worker+0x6c7/0x800 net/mptcp/protocol.c:2705
 process_one_work+0x3bd/0x950 kernel/workqueue.c:2390
 worker_thread+0x5b/0x610 kernel/workqueue.c:2537
 kthread+0x138/0x170 kernel/kthread.c:376
 ret_from_fork+0x2c/0x50 arch/x86/entry/entry_64.S:308
 </TASK>

This change addresses the issue explicitly checking for bad states
before running the mptcp worker.

The Linux kernel CVE team has assigned CVE-2023-54176 to this issue.


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

	Issue introduced in 5.11 with commit e16163b6e2b720fb74e5af758546f6dad27e6c9e and fixed in 5.15.108 with commit f0b4a4086cf27240fc621a560da9735159049dcc
	Issue introduced in 5.11 with commit e16163b6e2b720fb74e5af758546f6dad27e6c9e and fixed in 6.1.25 with commit aff9099e9c51f15c8def05c75b2b73e8487b5d54
	Issue introduced in 5.11 with commit e16163b6e2b720fb74e5af758546f6dad27e6c9e and fixed in 6.2.12 with commit 19ea79e87af32c2b3c6fc49bd84efeb35ca57678
	Issue introduced in 5.11 with commit e16163b6e2b720fb74e5af758546f6dad27e6c9e and fixed in 6.3 with commit d6a0443733434408f2cbd4c53fea6910599bab9e

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-2023-54176
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/mptcp/protocol.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/f0b4a4086cf27240fc621a560da9735159049dcc
	https://git.kernel.org/stable/c/aff9099e9c51f15c8def05c75b2b73e8487b5d54
	https://git.kernel.org/stable/c/19ea79e87af32c2b3c6fc49bd84efeb35ca57678
	https://git.kernel.org/stable/c/d6a0443733434408f2cbd4c53fea6910599bab9e