linux-cve-announce - CVE-2025-40139: smc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx

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Message-ID: <2025111255-CVE-2025-40139-a030@gregkh>
Date: Wed, 12 Nov 2025 19:24:15 +0900
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40139: smc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set().

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

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

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

smc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set().

smc_clc_prfx_set() is called during connect() and not under RCU
nor RTNL.

Using sk_dst_get(sk)->dev could trigger UAF.

Let's use __sk_dst_get() and dev_dst_rcu() under rcu_read_lock()
after kernel_getsockname().

Note that the returned value of smc_clc_prfx_set() is not used
in the caller.

While at it, we change the 1st arg of smc_clc_prfx_set[46]_rcu()
not to touch dst there.

The Linux kernel CVE team has assigned CVE-2025-40139 to this issue.

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

	Issue introduced in 4.11 with commit a046d57da19f812216f393e7c535f5858f793ac3 and fixed in 6.17.3 with commit 0736993bfe5c7a9c744ae3fac62d769dfdae54e1
	Issue introduced in 4.11 with commit a046d57da19f812216f393e7c535f5858f793ac3 and fixed in 6.18-rc1 with commit 935d783e5de9b64587f3adb25641dd8385e64ddb

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-2025-40139
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/smc/smc_clc.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/0736993bfe5c7a9c744ae3fac62d769dfdae54e1
	https://git.kernel.org/stable/c/935d783e5de9b64587f3adb25641dd8385e64ddb