CVE-2026-93097: cxl/mbox: Break poison list loop on an empty payload

CVE-2026-93097: cxl/mbox: Break poison list loop on an empty payload

[Greg Kroah-Hartman]

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

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

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

cxl/mbox: Break poison list loop on an empty payload

A device that returns count == 0 with CXL_POISON_FLAG_MORE set on every
iteration never advances nr_records, so the max_errors guard never
trips and the do/while loops forever while holding poison.mutex. That
hangs the sysfs-triggered scan thread and blocks all subsequent poison
operations on the device. The existing "Protect against an uncleared
_FLAG_MORE" guard was intended to bound a misbehaving device but does
not cover the count == 0 case.

Stop the loop on an empty payload so a malfunctioning or malicious
device cannot wedge the poison scan.

The Linux kernel CVE team has assigned CVE-2026-93097 to this issue.


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

	Issue introduced in 6.4 with commit ed83f7ca398b3798b82c1d5d1113011c0e5a2198 and fixed in 6.6.157 with commit 86771c105293ca26bfcc320b4f60d32c137b54aa
	Issue introduced in 6.4 with commit ed83f7ca398b3798b82c1d5d1113011c0e5a2198 and fixed in 6.12.110 with commit 42eab80981f4d2ac820e253e80ecf92f8cd91f69
	Issue introduced in 6.4 with commit ed83f7ca398b3798b82c1d5d1113011c0e5a2198 and fixed in 6.18.52 with commit 6ad491cef1a812cf7b53aa769cd8869516c47362
	Issue introduced in 6.4 with commit ed83f7ca398b3798b82c1d5d1113011c0e5a2198 and fixed in 7.2.6 with commit e77594e0cea67ab1c2317a27aa77a744e26ad6a6
	Issue introduced in 6.4 with commit ed83f7ca398b3798b82c1d5d1113011c0e5a2198 and fixed in 7.3-rc1 with commit 8b301c4afbce4bc3f94528441d8d5ce1366504ad

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-2026-93097
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/cxl/core/mbox.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/86771c105293ca26bfcc320b4f60d32c137b54aa
	https://git.kernel.org/stable/c/42eab80981f4d2ac820e253e80ecf92f8cd91f69
	https://git.kernel.org/stable/c/6ad491cef1a812cf7b53aa769cd8869516c47362
	https://git.kernel.org/stable/c/e77594e0cea67ab1c2317a27aa77a744e26ad6a6
	https://git.kernel.org/stable/c/8b301c4afbce4bc3f94528441d8d5ce1366504ad