linux-cve-announce - CVE-2025-23145: mptcp: fix NULL pointer in can_accept_new

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Message-ID: <2025050126-CVE-2025-23145-4a18@gregkh>
Date: Thu,  1 May 2025 14:56:25 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-23145: mptcp: fix NULL pointer in can_accept_new_subflow

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

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

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

mptcp: fix NULL pointer in can_accept_new_subflow

When testing valkey benchmark tool with MPTCP, the kernel panics in
'mptcp_can_accept_new_subflow' because subflow_req->msk is NULL.

Call trace:

  mptcp_can_accept_new_subflow (./net/mptcp/subflow.c:63 (discriminator 4)) (P)
  subflow_syn_recv_sock (./net/mptcp/subflow.c:854)
  tcp_check_req (./net/ipv4/tcp_minisocks.c:863)
  tcp_v4_rcv (./net/ipv4/tcp_ipv4.c:2268)
  ip_protocol_deliver_rcu (./net/ipv4/ip_input.c:207)
  ip_local_deliver_finish (./net/ipv4/ip_input.c:234)
  ip_local_deliver (./net/ipv4/ip_input.c:254)
  ip_rcv_finish (./net/ipv4/ip_input.c:449)
  ...

According to the debug log, the same req received two SYN-ACK in a very
short time, very likely because the client retransmits the syn ack due
to multiple reasons.

Even if the packets are transmitted with a relevant time interval, they
can be processed by the server on different CPUs concurrently). The
'subflow_req->msk' ownership is transferred to the subflow the first,
and there will be a risk of a null pointer dereference here.

This patch fixes this issue by moving the 'subflow_req->msk' under the
`own_req == true` conditional.

Note that the !msk check in subflow_hmac_valid() can be dropped, because
the same check already exists under the own_req mpj branch where the
code has been moved to.

The Linux kernel CVE team has assigned CVE-2025-23145 to this issue.

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

	Issue introduced in 5.9 with commit 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 and fixed in 6.1.135 with commit 855bf0aacd51fced11ea9aa0d5101ee0febaeadb
	Issue introduced in 5.9 with commit 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 and fixed in 6.6.88 with commit 7f9ae060ed64aef8f174c5f1ea513825b1be9af1
	Issue introduced in 5.9 with commit 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 and fixed in 6.12.24 with commit dc81e41a307df523072186b241fa8244fecd7803
	Issue introduced in 5.9 with commit 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 and fixed in 6.13.12 with commit efd58a8dd9e7a709a90ee486a4247c923d27296f
	Issue introduced in 5.9 with commit 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 and fixed in 6.14.3 with commit 4b2649b9717678aeb097893cc49f59311a1ecab0
	Issue introduced in 5.9 with commit 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 and fixed in 6.15-rc1 with commit 443041deb5ef6a1289a99ed95015ec7442f141dc

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-2025-23145
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/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/855bf0aacd51fced11ea9aa0d5101ee0febaeadb
	https://git.kernel.org/stable/c/7f9ae060ed64aef8f174c5f1ea513825b1be9af1
	https://git.kernel.org/stable/c/dc81e41a307df523072186b241fa8244fecd7803
	https://git.kernel.org/stable/c/efd58a8dd9e7a709a90ee486a4247c923d27296f
	https://git.kernel.org/stable/c/4b2649b9717678aeb097893cc49f59311a1ecab0
	https://git.kernel.org/stable/c/443041deb5ef6a1289a99ed95015ec7442f141dc