CVE-2026-89622: HID: mcp2221: clear rxbuf after I2C/SMBus transfer completes

CVE-2026-89622: HID: mcp2221: clear rxbuf after I2C/SMBus transfer completes

[Greg Kroah-Hartman]

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

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

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

HID: mcp2221: clear rxbuf after I2C/SMBus transfer completes

mcp_i2c_smbus_read() stores the caller-supplied buffer pointer in
mcp->rxbuf for the duration of a transfer but never clears it when the
transfer finishes or times out. Once the caller frees or reuses the
buffer, mcp->rxbuf becomes a dangling pointer. A delayed or spurious
MCP2221_I2C_GET_DATA report can then drive mcp2221_raw_event() to
memcpy device data into the freed memory, causing a write
use-after-free.

Route all return paths through a single exit point that clears
mcp->rxbuf and mcp->rxbuf_size, so that the existing !mcp->rxbuf guard
in the raw_event handler can reject any report arriving after the
transfer has ended.

The Linux kernel CVE team has assigned CVE-2026-89622 to this issue.


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

	Issue introduced in 5.7 with commit 67a95c21463d066060b0f66d65a75d45bb386ffb and fixed in 6.18.51 with commit 03c34309eb1bce1b3b5f7c4a94b703f419120383
	Issue introduced in 5.7 with commit 67a95c21463d066060b0f66d65a75d45bb386ffb and fixed in 7.2.4 with commit 968546b676d992dd1da3e057d40598231f725996
	Issue introduced in 5.7 with commit 67a95c21463d066060b0f66d65a75d45bb386ffb and fixed in 7.3-rc1 with commit db2333f88729c8aae062cb171ed058725ff5c901

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-2026-89622
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/hid/hid-mcp2221.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/03c34309eb1bce1b3b5f7c4a94b703f419120383
	https://git.kernel.org/stable/c/968546b676d992dd1da3e057d40598231f725996
	https://git.kernel.org/stable/c/db2333f88729c8aae062cb171ed058725ff5c901