CVE-2026-93079: cxl/features: Reject Get Feature count larger than the output buffer

CVE-2026-93079: cxl/features: Reject Get Feature count larger than the output buffer

[Greg Kroah-Hartman]

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

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

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

cxl/features: Reject Get Feature count larger than the output buffer

cxlctl_get_feature() sizes its output buffer from the user's
fwctl_rpc.out_len, but the device is told to write
cxl_mbox_get_feat_in.count bytes into rpc_out->payload, which is a
separate user-controlled value. Nothing bounds count against out_len, so
a small out_len with a large count overflows the kvzalloc()'d buffer.
A heap OOB write reachable from FWCTL_RPC.

Reject requests where count exceeds the available payload room, before
allocating.

The Linux kernel CVE team has assigned CVE-2026-93079 to this issue.


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

	Issue introduced in 6.15 with commit 5908f3ed6dc209e5c824e63afda7545805f75a7e and fixed in 6.18.52 with commit 3f02031a0a53de0d3ef066c92d0486b2b11be40c
	Issue introduced in 6.15 with commit 5908f3ed6dc209e5c824e63afda7545805f75a7e and fixed in 7.2.6 with commit 329ea475581c647a680a6937e353c1a6e2534b40
	Issue introduced in 6.15 with commit 5908f3ed6dc209e5c824e63afda7545805f75a7e and fixed in 7.3-rc1 with commit 4bf6bac375076ced2fa4b3fef8739bd985f93456

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-2026-93079
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/3f02031a0a53de0d3ef066c92d0486b2b11be40c
	https://git.kernel.org/stable/c/329ea475581c647a680a6937e353c1a6e2534b40
	https://git.kernel.org/stable/c/4bf6bac375076ced2fa4b3fef8739bd985f93456