CVE-2026-89571: cxl/features: bound fwctl command payload to the input buffer

CVE-2026-89571: cxl/features: bound fwctl command payload to the input buffer

[Greg Kroah-Hartman]

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

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

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

cxl/features: bound fwctl command payload to the input buffer

fwctl_cmd_rpc() copies cmd->in_len bytes into inbuf = kvzalloc(cmd->in_len)
and passes inbuf and in_len to ->fw_rpc(). The CXL callback cxlctl_fw_rpc()
ignores in_len and never checks the user-controlled op_size against it.

cxlctl_set_feature() bounds op_size only from below
(op_size <= sizeof(feat_in->hdr)) and then reads op_size - sizeof(hdr)
bytes from feat_in->feat_data via cxl_set_feature(). With a small in_len
and a large op_size the first memcpy() already reads past the
kvzalloc(in_len) buffer; the out-of-bounds bytes are placed in the mailbox
payload and sent to the device, and a large enough op_size can walk into
unmapped memory and oops the kernel. The Get paths pin op_size to a fixed
size but likewise read the input struct without checking in_len.

Reject, at the single dispatch point, any request whose fixed header plus
op_size does not fit in the copied-in buffer. The lower-bound test guards
the subtraction and ensures op_size was copied in before it is read.

The Linux kernel CVE team has assigned CVE-2026-89571 to this issue.


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

	Issue introduced in 6.15 with commit eb5dfcb9e36d0e46089fec777d911313c1876fa3 and fixed in 6.18.50 with commit 14d52c15d5d99477b20a2d61fe36f347080da6cd
	Issue introduced in 6.15 with commit eb5dfcb9e36d0e46089fec777d911313c1876fa3 and fixed in 7.2.4 with commit d8957545fe96f7905791c937758ebfc1ae1e5b17
	Issue introduced in 6.15 with commit eb5dfcb9e36d0e46089fec777d911313c1876fa3 and fixed in 7.3-rc1 with commit f687394af983df5660b6afae7e0d06969f3af206

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-2026-89571
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/14d52c15d5d99477b20a2d61fe36f347080da6cd
	https://git.kernel.org/stable/c/d8957545fe96f7905791c937758ebfc1ae1e5b17
	https://git.kernel.org/stable/c/f687394af983df5660b6afae7e0d06969f3af206