CVE-2024-56755

What it actually does

Missing memory barrier between bit-clearing operation and wake-up in fscache_create_volume() allows concurrent cookie processes to miss the cleared bit state after wakeup, resulting in indefinite wait on the same volume.

Why it matters to the business

May cause hangs or stalled cache operations on Linux systems using fscache, reducing availability for file-system dependent workloads; low exploitation likelihood and no ransomware association reduce urgency despite broad kernel presence.

How an attack unfolds

Local processes performing simultaneous fscache lookups on a shared volume trigger the race: one clears the bit and wakes while the other sets the bit and enters wait without seeing the update due to absent ordering, leaving the waiter blocked; general Linux kernel threat activity noted but no specific actors tied to this flaw.

How to fix it

Upgrade affected chromium-browser packages on Ubuntu 14.04 LTS to version 52.0.2743.116-0ubuntu0.14.04.1.1134; apply kernel updates incorporating clear_and_wake_up_bit() into fscache_create_volume().

How to confirm the fix worked

Inspect fscache_create_volume() source for combined clear_and_wake_up_bit() usage or verify updated kernel/chromium packages are installed and test concurrent volume creation workloads for absence of hangs.

Typical attack path

1. Identify or create conditions for concurrent fscache volume creation on identical volumes
2. Spawn multiple processes executing fscache_perform_lookup and fscache_create_volume
3. Trigger bit set, clear, and wakeup sequence across cookies
4. Observe one process entering indefinite wait state

How to detect it

Review kernel logs and process traces for stuck tasks in fscache volume creation paths; correlate with concurrent lookup activity on shared volumes.

What your security team should do

• Apply listed package updates to fixed versions without delay
• Monitor system logs and process states for fscache-related waits
• Prioritize testing on systems with heavy fscache usage