Bug 2516414 (CVE-2026-72142)

Summary: CVE-2026-72142 kernel: i2c: imx: fix locked bus on SMBus block-read of 0 (atomic)
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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OS: Linux   
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A flaw was found in the i2c-imx driver of the Linux kernel. When an I2C slave device performs an SMBus block-read operation with a byte count of zero, the atomic (polling) path in the driver fails to properly release the I2C bus. This can cause the bus to become stuck, requiring a power cycle of the I2C controller to restore functionality. This issue leads to a denial of service for the affected system.
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Description OSIDB Bzimport 2026-08-15 06:11:15 UTC 
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.
Comment 1 gkamathe 2026-08-18 09:29:50 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081532-CVE-2026-72142-616e@gregkh/T