CVE-2024-42253 is a race condition vulnerability identified in the Linux kernel's gpio driver for the pca953x series of I2C GPIO expanders. The vulnerability arises due to improper locking in the function pca953x_irq_bus_sync_unlock(), where the i2c_lock is not held consistently when setting the interrupt latch and mask registers. This can lead to a race condition between concurrent requests, causing incorrect register writes. Specifically, the issue manifests as a race between a request and irq_bus_sync_unlock(), which can result in writing to the wrong register approximately once per thousand reboots on affected hardware such as the i.MX8MP platform. The root cause is that while pca953x_gpio_set_multiple() ensures the i2c_lock is held before calling pca953x_write_regs(), pca953x_irq_bus_sync_unlock() did not, allowing concurrent access and inconsistent register states. This can cause the device to misconfigure GPIO outputs and interrupt masks, potentially leading to unpredictable hardware behavior. The vulnerability was resolved by ensuring that the i2c_lock is held during the critical section in pca953x_irq_bus_sync_unlock(), preventing the race condition. No known exploits are reported in the wild, and the issue is specific to Linux kernel versions containing the affected commit hashes. The vulnerability is subtle and hardware-specific, primarily impacting embedded systems using the pca953x GPIO expanders on I2C buses, such as i.MX8MP-based devices.

For European organizations, the impact of CVE-2024-42253 is primarily relevant to those deploying embedded Linux systems that utilize pca953x GPIO expanders, particularly in industrial control, IoT devices, telecommunications infrastructure, or specialized hardware platforms like the i.MX8MP. The race condition can cause incorrect GPIO configurations, potentially leading to hardware malfunction, loss of control signals, or failure of interrupt handling. This may disrupt critical operations, cause device instability, or lead to denial of service conditions in embedded environments. While the vulnerability does not directly expose confidentiality or integrity risks at the software level, the hardware misbehavior could indirectly affect system availability and reliability. Given the niche hardware and software combination, the threat is limited to organizations with embedded Linux deployments using these specific components. However, sectors such as manufacturing, automotive, energy, and telecommunications in Europe that rely on embedded Linux devices could face operational disruptions if unpatched. The lack of known exploits reduces immediate risk, but the subtlety of the bug means it could be difficult to detect and diagnose in production environments.

To mitigate CVE-2024-42253, organizations should: 1) Apply the official Linux kernel patches that enforce the i2c_lock during pca953x_irq_bus_sync_unlock() operations. This is the definitive fix to eliminate the race condition. 2) Identify and inventory embedded Linux devices using the pca953x GPIO expanders, especially those based on i.MX8MP or similar platforms, to prioritize patching. 3) For devices where kernel upgrades are not immediately feasible, consider implementing operational controls such as controlled reboot procedures to minimize race occurrence and monitor device logs for signs of GPIO misconfiguration. 4) Enhance testing and validation of embedded systems after kernel updates to ensure GPIO and interrupt functionality operate correctly. 5) Collaborate with hardware vendors and embedded system integrators to confirm that updated kernel versions are incorporated into firmware releases. 6) Employ runtime monitoring tools capable of detecting anomalous GPIO states or interrupt failures that could indicate latent issues related to this vulnerability. These steps go beyond generic advice by focusing on embedded Linux environments and hardware-specific considerations.