linux-cve-announce - CVE-2025-40106: comedi: fix divide-by-zero in comedi_buf

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Message-ID: <2025103155-CVE-2025-40106-ed47@gregkh>
Date: Fri, 31 Oct 2025 10:41:56 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40106: comedi: fix divide-by-zero in comedi_buf_munge()

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

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

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

comedi: fix divide-by-zero in comedi_buf_munge()

The comedi_buf_munge() function performs a modulo operation
`async->munge_chan %= async->cmd.chanlist_len` without first
checking if chanlist_len is zero. If a user program submits a command with
chanlist_len set to zero, this causes a divide-by-zero error when the device
processes data in the interrupt handler path.

Add a check for zero chanlist_len at the beginning of the
function, similar to the existing checks for !map and
CMDF_RAWDATA flag. When chanlist_len is zero, update
munge_count and return early, indicating the data was
handled without munging.

This prevents potential kernel panics from malformed user commands.

The Linux kernel CVE team has assigned CVE-2025-40106 to this issue.


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

	Fixed in 5.4.301 with commit 4ffea48c69cb2b96a281cb7e5e42d706996631db
	Fixed in 5.10.246 with commit 8f3e4cd9be4b47246ea73ce5e3e0fa2f57f0d10c
	Fixed in 5.15.196 with commit 2670932f2465793fea1ef073e40883e8390fa4d9
	Fixed in 6.1.158 with commit 6db19822512396be1a3e1e20c16c97270285ba1a
	Fixed in 6.6.115 with commit d4854eff25efb06d0d84c13e7129bbdba4125f8c
	Fixed in 6.12.56 with commit a4bb5d1bc2f238461bcbe5303eb500466690bb2c
	Fixed in 6.17.6 with commit 55520f65fd447e04099a2c44185453c18ea73b7e
	Fixed in 6.18-rc3 with commit 87b318ba81dda2ee7b603f4f6c55e78ec3e95974

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-2025-40106
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/comedi/comedi_buf.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/4ffea48c69cb2b96a281cb7e5e42d706996631db
	https://git.kernel.org/stable/c/8f3e4cd9be4b47246ea73ce5e3e0fa2f57f0d10c
	https://git.kernel.org/stable/c/2670932f2465793fea1ef073e40883e8390fa4d9
	https://git.kernel.org/stable/c/6db19822512396be1a3e1e20c16c97270285ba1a
	https://git.kernel.org/stable/c/d4854eff25efb06d0d84c13e7129bbdba4125f8c
	https://git.kernel.org/stable/c/a4bb5d1bc2f238461bcbe5303eb500466690bb2c
	https://git.kernel.org/stable/c/55520f65fd447e04099a2c44185453c18ea73b7e
	https://git.kernel.org/stable/c/87b318ba81dda2ee7b603f4f6c55e78ec3e95974