linux-cve-announce - CVE-2025-40071: tty: n_gsm: Don't block input queue by waiting MSC

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Message-ID: <2025102818-CVE-2025-40071-6cff@gregkh>
Date: Tue, 28 Oct 2025 12:48:48 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40071: tty: n_gsm: Don't block input queue by waiting MSC

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

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

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

tty: n_gsm: Don't block input queue by waiting MSC

Currently gsm_queue() processes incoming frames and when opening
a DLC channel it calls gsm_dlci_open() which calls gsm_modem_update().
If basic mode is used it calls gsm_modem_upd_via_msc() and it
cannot block the input queue by waiting the response to come
into the same input queue.

Instead allow sending Modem Status Command without waiting for remote
end to respond. Define a new function gsm_modem_send_initial_msc()
for this purpose. As MSC is only valid for basic encoding, it does
not do anything for advanced or when convergence layer type 2 is used.

The Linux kernel CVE team has assigned CVE-2025-40071 to this issue.


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

	Issue introduced in 5.18 with commit 48473802506d2d6151f59e0e764932b33b53cb3b and fixed in 6.6.112 with commit c36785f9de03df56ff9b8eca30fa681a12b2310d
	Issue introduced in 5.18 with commit 48473802506d2d6151f59e0e764932b33b53cb3b and fixed in 6.12.53 with commit 5416e89b81b00443cb03c88df8da097ae091a141
	Issue introduced in 5.18 with commit 48473802506d2d6151f59e0e764932b33b53cb3b and fixed in 6.17.3 with commit c5a2791a7f11939f05f95c01f0aec0c55bbf28d5
	Issue introduced in 5.18 with commit 48473802506d2d6151f59e0e764932b33b53cb3b and fixed in 6.18-rc1 with commit 3cf0b3c243e56bc43be560617416c1d9f301f44c
	Issue introduced in 5.15.54 with commit 920e849b7d23ced84c9d11e11e2449e34973cfb8
	Issue introduced in 5.17.6 with commit e83b4e1540469babeffcfd44a605cf8a61542598

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-2025-40071
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:
	drivers/tty/n_gsm.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/c36785f9de03df56ff9b8eca30fa681a12b2310d
	https://git.kernel.org/stable/c/5416e89b81b00443cb03c88df8da097ae091a141
	https://git.kernel.org/stable/c/c5a2791a7f11939f05f95c01f0aec0c55bbf28d5
	https://git.kernel.org/stable/c/3cf0b3c243e56bc43be560617416c1d9f301f44c