CVE-2024-50230

What it actually does

Missing clearing of the checked flag on discarded pages/folios in nilfs2 causes directory entry sanity checks to be skipped on reload, leading to BUG_ON failure in __block_write_begin_int() for accesses exceeding folio/page size after read-only degradation on corruption detection.

Why it matters to the business

Kernel crashes or instability on affected Linux systems using nilfs2 after corruption events, resulting in potential downtime and data access issues; low urgency given no KEV status, stable low EPSS, and dated publication.

How an attack unfolds

An attacker with local access triggers nilfs2 corruption detection to force read-only mode, then performs directory operations that cause discarded pages to reload without the checked flag cleared, skipping sanity checks and hitting the kernel BUG_ON during block write preparation.

How to fix it

Upgrade affected packages to the listed fixed versions: flashplugin-nonfree (Ubuntu:14.04:LTS) fixed in 11.2.202.535ubuntu0.14.04.1. Apply kernel updates addressing nilfs2 page handling where available.

How to confirm the fix worked

Confirm kernel version or package installation matches fixed releases; test directory operations on nilfs2 after simulated corruption to verify no BUG_ON triggers.

Typical attack path

1. Gain local access to system using nilfs2
2. Induce or wait for filesystem corruption detection
3. Execute directory operations triggering page discard and reload
4. Trigger BUG_ON check failure in block write path

How to detect it

Review system logs for nilfs2 corruption messages followed by BUG_ON panics or page faults in block write paths; inspect for repeated directory operation failures post-degradation.

What your security team should do

• Prioritize kernel and filesystem package updates on systems using nilfs2
• Monitor for nilfs2 corruption events in logs
• Restrict local user access where possible until patched