CVE-2024-42253

What it actually does

Missing i2c_lock acquisition in pca953x_irq_bus_sync_unlock permits concurrent writes that target incorrect I2C registers instead of the intended latch/mask registers.

Why it matters to the business

Rare timing-dependent GPIO configuration errors on affected Linux systems can produce intermittent hardware control failures, especially during reboot or high IRQ activity on embedded platforms.

How an attack unfolds

An attacker able to trigger rapid concurrent GPIO and interrupt operations races the unlock path to corrupt register programming; the window occurs roughly once per thousand reboots and requires local code execution or crafted IRQ load.

How to fix it

Upgrade the Linux kernel to a version containing commit 58a5c93bd1a6e949267400080f07e57ffe05ec34; AlmaLinux users should update listed dnf-plugins-core packages to 4.0.21-11.el8 or later.

How to confirm the fix worked

Confirm the fix commit is present in the running kernel source tree and re-run the original race reproducer under reboot loops to verify absence of interleaved writes.

Typical attack path

1. Initiate concurrent pca953x_gpio_set_multiple and IRQ bus sync operations
2. Exploit missing lock to interleave register writes
3. Cause write to wrong register (e.g., output instead of latch)
4. Result in incorrect pin configuration or mask state

How to detect it

Review kernel logs and I2C traces around boot or IRQ storms for unexpected register addresses or values written to pca953x devices; correlate with pca953x driver messages.

What your security team should do

• Apply kernel updates containing the referenced commit on all systems using pca953x GPIO expanders
• Prioritize patching for embedded or i.MX8MP deployments due to observed race frequency
• Include the driver in regression test suites for IRQ and GPIO paths