CVE-2024-47700

What it actually does

Missing validation of stripe size compatibility with cluster ratio during ext4 remount allows EXT4_B2C(sbi->s_stripe) to evaluate to 0, enabling divide-by-zero conditions.

Why it matters to the business

Potential kernel crashes or unexpected filesystem behavior on systems performing remount operations with specific stripe and cluster settings, increasing operational risk and downtime.

How an attack unfolds

An attacker with sufficient privileges to trigger or influence an ext4 remount supplies a stripe size incompatible with the cluster ratio, bypassing the check present only in initial mount and causing arithmetic faults during subsequent operations.

How to fix it

Apply the kernel fix that adds the stripe compatibility check to the remount path; for roundup (PyPI) instances update to version 2.4.0.

How to confirm the fix worked

Confirm presence of the remount-path stripe check in source or running kernel; test remount with non-multiple stripe sizes and verify no divide-by-zero occurs.

Typical attack path

1. Identify ext4 filesystem with stripe and cluster configuration
2. Trigger or perform remount with incompatible stripe value
3. Trigger code paths that compute EXT4_B2C on s_stripe leading to division by zero

How to detect it

Review kernel logs for ext4 remount events followed by divide-by-zero or arithmetic exceptions; inspect mount options and superblock stripe values around the time of crashes.

What your security team should do

• Prioritize kernel updates containing the remount validation fix
• Audit ext4 mount/remount scripts and configurations for stripe/cluster settings
• Monitor for kernel oops or divide-by-zero panics involving ext4