CVE-2026-93078: cxl/features: Reject Set Features output buffer smaller than the header

CVE-2026-93078: cxl/features: Reject Set Features output buffer smaller than the header

[Greg Kroah-Hartman]

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

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

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

cxl/features: Reject Set Features output buffer smaller than the header

cxlctl_set_feature() sizes its output buffer from the user's
fwctl_rpc.out_len but never checks it is large enough to hold even the
fwctl_rpc_cxl_out header. With out_len == 0 , kvzalloc() returns
ZERO_SIZE_PTR, which passes the !rpc_out check, the subsequent
rpc_out->size = 0 then writes through the poison pointer.

Reject requests whose output buffer can't hold the response header,
before allocating. The Set Feature reply carries no payload, so the
header is all that is required.

The Linux kernel CVE team has assigned CVE-2026-93078 to this issue.


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

	Issue introduced in 6.15 with commit eb5dfcb9e36d0e46089fec777d911313c1876fa3 and fixed in 6.18.52 with commit 1281dc84c81577b51e2b61c24617c9f44b2cdb99
	Issue introduced in 6.15 with commit eb5dfcb9e36d0e46089fec777d911313c1876fa3 and fixed in 7.2.6 with commit 16b7c99eff030c6ea11ca24efa4b9f989cc74093
	Issue introduced in 6.15 with commit eb5dfcb9e36d0e46089fec777d911313c1876fa3 and fixed in 7.3-rc1 with commit cde18d6c1d913a67ab0afd3d9475ece4be79da50

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-2026-93078
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/features.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/1281dc84c81577b51e2b61c24617c9f44b2cdb99
	https://git.kernel.org/stable/c/16b7c99eff030c6ea11ca24efa4b9f989cc74093
	https://git.kernel.org/stable/c/cde18d6c1d913a67ab0afd3d9475ece4be79da50