linux-cve-announce - CVE-2025-40170: net: use dst_dev_rcu() in sk_setup

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Message-ID: <2025111259-CVE-2025-40170-d39d@gregkh>
Date: Wed, 12 Nov 2025 05:46:57 -0500
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40170: net: use dst_dev_rcu() in sk_setup_caps()

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

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

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

net: use dst_dev_rcu() in sk_setup_caps()

Use RCU to protect accesses to dst->dev from sk_setup_caps()
and sk_dst_gso_max_size().

Also use dst_dev_rcu() in ip6_dst_mtu_maybe_forward(),
and ip_dst_mtu_maybe_forward().

ip4_dst_hoplimit() can use dst_dev_net_rcu().

The Linux kernel CVE team has assigned CVE-2025-40170 to this issue.


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

	Issue introduced in 4.13 with commit 4a6ce2b6f2ecabbddcfe47e7cf61dd0f00b10e36 and fixed in 6.17.3 with commit a805729c0091073d8f0415cfa96c7acd1bc17a48
	Issue introduced in 4.13 with commit 4a6ce2b6f2ecabbddcfe47e7cf61dd0f00b10e36 and fixed in 6.18-rc1 with commit 99a2ace61b211b0be861b07fbaa062fca4b58879

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-2025-40170
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:
	include/net/ip.h
	include/net/ip6_route.h
	include/net/route.h
	net/core/sock.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/a805729c0091073d8f0415cfa96c7acd1bc17a48
	https://git.kernel.org/stable/c/99a2ace61b211b0be861b07fbaa062fca4b58879