CVE-2026-72141: i2c: imx: fix locked bus on SMBus block-read of 0 (IRQ)

CVE-2026-72141: i2c: imx: fix locked bus on SMBus block-read of 0 (IRQ)

[Greg Kroah-Hartman]

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

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

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

i2c: imx: fix locked bus on SMBus block-read of 0 (IRQ)

SMBus 3.1 6.5.7 allows a Block Read byte count of 0, but the
interrupt-driven block-read state machine rejects it as -EPROTO. Worse,
it returns without a NACK+STOP: the next receive cycle has already
started, so the target keeps holding SDA and the bus stays stuck until a
power cycle of this i2c controller.

Accept count=0: NACK the in-flight dummy byte (TXAK) and set msg->len to
2 so i2c_imx_isr_read_continue() emits STOP via its normal last-byte
path. The dummy byte is discarded; block-read callers only consume
buf[0..count-1].

Reading I2DR has likewise already armed the next byte on the
count > I2C_SMBUS_BLOCK_MAX error path, so NACK it (TXAK) before aborting
with -EPROTO; otherwise the failing transfer's STOP cannot complete and
the bus stays held.

The atomic path regressed earlier (v3.16) and is fixed separately; this
patch covers only the v6.13 state-machine rework.

The Linux kernel CVE team has assigned CVE-2026-72141 to this issue.


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

	Issue introduced in 6.13 with commit 5f5c2d4579ca6836f5604cca979debd68ecfe23f and fixed in 6.18.40 with commit 5d3240f42a667e29262aff76fdebfcdac4980626
	Issue introduced in 6.13 with commit 5f5c2d4579ca6836f5604cca979debd68ecfe23f and fixed in 7.1.5 with commit 56ddfc18ea8f7d77747658892873eb632b2ed530
	Issue introduced in 6.13 with commit 5f5c2d4579ca6836f5604cca979debd68ecfe23f and fixed in 7.2-rc4 with commit 07fd9385f0d87dff4b34f355f68adf701080cb24

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-2026-72141
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-imx.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/5d3240f42a667e29262aff76fdebfcdac4980626
	https://git.kernel.org/stable/c/56ddfc18ea8f7d77747658892873eb632b2ed530
	https://git.kernel.org/stable/c/07fd9385f0d87dff4b34f355f68adf701080cb24