CVE-2026-64205: i2c: i801: fix hardware state machine corruption in error path

From: Greg Kroah-Hartman <[email protected]>

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

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

i2c: i801: fix hardware state machine corruption in error path

A severe livelock and subsequent Hung Task panic were observed in the
i2c-i801 driver during concurrent Fuzzing. The crash is caused by an
unconditional hardware register cleanup in the error handling path of
i801_access().

When i801_check_pre() fails (e.g., returning -EBUSY because the SMBus
controller is actively used by BIOS/ACPI), the kernel does not actually
acquire the hardware ownership. However, the code jumps to the 'out'
label and executes:

    iowrite8(SMBHSTSTS_INUSE_STS | STATUS_FLAGS, SMBHSTSTS(priv));

This forcefully clears the INUSE_STS lock and resets the hardware status
flags without owning the controller. Doing so interrupts ongoing BIOS/ACPI
transactions and totally corrupts the SMBus hardware state machine.

Consequently, all subsequent i801_access() calls fail at the pre-check
stage, triggering an endless stream of "SMBus is busy, can't use it!"
error logs. Over a slow serial console, this printk flood monopolizes
the CPU (Console Livelock), starving other processes trying to acquire
the mmap_lock down_read semaphore, ultimately triggering the hung task
watchdog.

Fix this by moving the 'out' label below the hardware register cleanup.
If i801_check_pre() fails, we safely bypass the iowrite8() and only
release the software locks (pm_runtime and mutex), strictly adhering to
the rule of not releasing resources that were never acquired.

The Linux kernel CVE team has assigned CVE-2026-64205 to this issue.


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

	Issue introduced in 6.3 with commit 1f760b87e54cf56a25ab68f8dc625e339f6e46d5 and fixed in 6.18.39 with commit bb5133a7d5f3fe5c387770e25f2e00e682ce11ed
	Issue introduced in 6.3 with commit 1f760b87e54cf56a25ab68f8dc625e339f6e46d5 and fixed in 7.1.4 with commit 00904687b9c5527d569d9a1ca72119823e735a61
	Issue introduced in 6.3 with commit 1f760b87e54cf56a25ab68f8dc625e339f6e46d5 and fixed in 7.2-rc1 with commit 10dd1a736d557e310a77117832874729a0175d57

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-2026-64205
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/i2c/busses/i2c-i801.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/bb5133a7d5f3fe5c387770e25f2e00e682ce11ed
	https://git.kernel.org/stable/c/00904687b9c5527d569d9a1ca72119823e735a61
	https://git.kernel.org/stable/c/10dd1a736d557e310a77117832874729a0175d57