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

Official 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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/5d3240f42a667e29262aff76fdebfcdac4980626
• https://git.kernel.org/stable/c/56ddfc18ea8f7d77747658892873eb632b2ed530
• https://git.kernel.org/stable/c/07fd9385f0d87dff4b34f355f68adf701080cb24