linux-cve-announce - CVE-2023-53072: mptcp: use the workqueue to destroy unaccepted sockets

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Message-ID: <2025050213-CVE-2023-53072-4ab2@gregkh>
Date: Fri,  2 May 2025 17:55:37 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53072: mptcp: use the workqueue to destroy unaccepted sockets

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

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

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

mptcp: use the workqueue to destroy unaccepted sockets

Christoph reported a UaF at token lookup time after having
refactored the passive socket initialization part:

  BUG: KASAN: use-after-free in __token_bucket_busy+0x253/0x260
  Read of size 4 at addr ffff88810698d5b0 by task syz-executor653/3198

  CPU: 1 PID: 3198 Comm: syz-executor653 Not tainted 6.2.0-rc59af4eaa31c1f6c00c8f1e448ed99a45c66340dd5 #6
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   <TASK>
   dump_stack_lvl+0x6e/0x91
   print_report+0x16a/0x46f
   kasan_report+0xad/0x130
   __token_bucket_busy+0x253/0x260
   mptcp_token_new_connect+0x13d/0x490
   mptcp_connect+0x4ed/0x860
   __inet_stream_connect+0x80e/0xd90
   tcp_sendmsg_fastopen+0x3ce/0x710
   mptcp_sendmsg+0xff1/0x1a20
   inet_sendmsg+0x11d/0x140
   __sys_sendto+0x405/0x490
   __x64_sys_sendto+0xdc/0x1b0
   do_syscall_64+0x3b/0x90
   entry_SYSCALL_64_after_hwframe+0x72/0xdc

We need to properly clean-up all the paired MPTCP-level
resources and be sure to release the msk last, even when
the unaccepted subflow is destroyed by the TCP internals
via inet_child_forget().

We can re-use the existing MPTCP_WORK_CLOSE_SUBFLOW infra,
explicitly checking that for the critical scenario: the
closed subflow is the MPC one, the msk is not accepted and
eventually going through full cleanup.

With such change, __mptcp_destroy_sock() is always called
on msk sockets, even on accepted ones. We don't need anymore
to transiently drop one sk reference at msk clone time.

Please note this commit depends on the parent one:

  mptcp: refactor passive socket initialization

The Linux kernel CVE team has assigned CVE-2023-53072 to this issue.


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

	Issue introduced in 5.7 with commit 58b09919626bf9067345289212ec030c61eb1034 and fixed in 6.1.22 with commit 2827f099b3fb9a59263c997400e9182f5d423e84
	Issue introduced in 5.7 with commit 58b09919626bf9067345289212ec030c61eb1034 and fixed in 6.2.8 with commit 804cf487fb0031f3c74755b78d8663333f0ba636
	Issue introduced in 5.7 with commit 58b09919626bf9067345289212ec030c61eb1034 and fixed in 6.3 with commit b6985b9b82954caa53f862d6059d06c0526254f0

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-2023-53072
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
	net/mptcp/protocol.h
	net/mptcp/subflow.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/2827f099b3fb9a59263c997400e9182f5d423e84
	https://git.kernel.org/stable/c/804cf487fb0031f3c74755b78d8663333f0ba636
	https://git.kernel.org/stable/c/b6985b9b82954caa53f862d6059d06c0526254f0