CVE-2026-72142i2c: imx: fix locked bus on SMBus block-read of 0 (atomic)

Official description

In the Linux kernel, the following vulnerability has been resolved: i2c: imx: fix locked bus on SMBus block-read of 0 (atomic) SMBus 3.1 6.5.7 allows a Block Read byte count of 0, but the atomic (polling) path 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 for this i2c controller. Reading I2DR to obtain the count likewise arms the next byte on the count > I2C_SMBUS_BLOCK_MAX path, which also returned -EPROTO directly and left the bus held. Handle both: NACK the in-flight dummy byte (TXAK) and extend msgs->len so the existing last-byte handling emits STOP; the dummy byte is discarded. A count of 0 is a valid empty block read; a count above I2C_SMBUS_BLOCK_MAX is still reported as -EPROTO, but only after the bus has been released. The interrupt-driven path has the same flaw from a later commit and is fixed separately, as it carries a different Fixes: tag and stable range.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/0f29df3c3d607a9dbc14aed0e45504ced4d2e7ec
• https://git.kernel.org/stable/c/38d4947431b2410850409fda016b2ac9f640a4dd
• https://git.kernel.org/stable/c/e3e8b02d4773cfc5ad561d2e5505efde36c6927a
• https://git.kernel.org/stable/c/016ef0f6ca4bc9bf0330ac41bd2ea349759643e3
• https://git.kernel.org/stable/c/c882e8cc68fb993700dc21fd6e754001e6297934
• https://git.kernel.org/stable/c/6d2c973926d0612360693bc559be2ffde836151b
• https://git.kernel.org/stable/c/60ed00d46616a9232e42ea7a3e3c0273d7cf7543
• https://git.kernel.org/stable/c/cb2fc37857693b55909fb77dc2c87cfbc1cdc476