CVE-2025-21712

What it actually does

The vulnerability allows bitmap_get_stats() to dereference a bitmap structure that has been destroyed or not fully initialized, leading to a general protection fault and kernel panic when mddev remains present.

Why it matters to the business

Causes unexpected system crashes and denial of service on affected Linux-based systems, with the issue reported over 600 days ago and showing stable low exploitation probability.

How an attack unfolds

A local attacker triggers md_seq_show which invokes bitmap_get_stats after bitmap destruction or incomplete initialization; related threat actor activity around similar Linux kernel privilege escalation issues can be monitored for context.

How to fix it

Apply the synchronization fix using bitmap_info.mutex in bitmap_get_stats; for octavia deployments update to version 3.1.0.

How to confirm the fix worked

Verify the mutex protection is present in bitmap_get_stats, test md bitmap operations post-update, and confirm absence of general protection faults in kernel logs during stats queries.

Typical attack path

1. Obtain local user access on the target system
2. Perform operations that destroy or delay bitmap initialization while mddev persists
3. Invoke paths calling bitmap_get_stats via seq_read or proc interfaces
4. Trigger dereference of invalid bitmap storage resulting in kernel panic

How to detect it

Search system logs for general protection faults and call traces involving bitmap_get_stats and md_seq_show; correlate with processes accessing md bitmap statistics.

What your security team should do

• Prioritize patching affected kernels or upgrading octavia to 3.1.0
• Monitor kernel logs for bitmap_get_stats related oops messages
• Limit local access where possible until remediation is complete