CVE-2024-39508

What it actually does

Data race on io_worker->flags due to non-atomic read/write operations across multiple CPUs in io_worker_handle_work and io_wq_activate_free_worker, allowing concurrent access without synchronization.

Why it matters to the business

Linux systems relying on io_uring for high-performance I/O may experience instability, crashes, or unpredictable behavior under concurrent workloads, increasing operational risk especially in servers and containers.

How an attack unfolds

An attacker triggers concurrent io_uring operations that cause multiple tasks to access worker flags simultaneously; the race can be leveraged to corrupt state and potentially escalate privileges, though no public exploits are known despite mentions of Android kernel RCE attempts.

How to fix it

Update the Linux kernel to the fixed commit ab702c3483db9046bab9f40306f1a28b22dbbdc0 or later stable versions that replace bitwise operations with set_bit/test_bit/clear_bit on worker->flags and adjust create_index placement.

How to confirm the fix worked

Confirm kernel source contains the atomic bit operations in io-wq.c and that KCSAN reports no data races for io_worker_handle_work and io_wq_activate_free_worker; test with io_uring stress workloads.

Typical attack path

1. Identify a target using io_uring for I/O operations
2. Craft a sequence of submissions and task work that activates io_wq_enqueue and io_worker_handle_work concurrently
3. Race the flag updates to induce memory corruption or invalid worker state
4. Escalate to kernel-level impact such as denial of service or code execution

How to detect it

Examine kernel logs for KCSAN data-race reports involving io_worker_handle_work and io_wq_activate_free_worker; review audit and system call logs for unusual io_uring activity patterns around the time of crashes or restarts.

What your security team should do

• Prioritize kernel updates on all systems using io_uring
• Monitor for upstream stable releases containing the referenced commit
• Disable io_uring via sysctl where not required as a temporary mitigation
• Review container and VM base images for vulnerable kernel versions