The Linux kernel gpio pca953x driver disables locking in the regmap configuration because it uses its own lock mechanism. All regmap read and write calls must hold the i2c_lock to ensure thread safety. The function pca953x_irq_bus_sync_unlock did not hold this lock during regmap reads, allowing potential concurrent access by multiple threads to incorrect registers. This flaw was partially fixed previously by protecting writes to the interrupt mask register but did not cover reads from the direction register. The vulnerability has now been resolved.

Without proper locking, concurrent threads could read or write incorrect registers, potentially causing inconsistent or unintended behavior in the gpio pca953x driver. This could affect system stability or correctness of GPIO operations relying on this driver. No direct exploit or impact on confidentiality, integrity, or availability is described.

A fix has been applied to the Linux kernel gpio pca953x driver to ensure that the i2c_lock is held during all regmap read and write operations, including in pca953x_irq_bus_sync_unlock. Users should update to the fixed kernel version once available. Patch status is not yet confirmed—check the vendor advisory or Linux kernel mailing lists for the specific patch and version details.