CVE-2024-56369

What it actually does

Insufficient validation in drm_mode_vrefresh allows vtotal*htotal product to reach zero, triggering a divide-by-zero exception during refresh rate calculation.

Why it matters to the business

Systems may experience kernel crashes or denial of service when handling certain display modes, interrupting graphics workloads and requiring reboots.

How an attack unfolds

An attacker supplies a crafted DRM mode object with zero or near-zero totals that bypass the existing htotal/vtotal guards; the kernel then performs the unchecked multiplication and division, causing a panic.

How to fix it

Upgrade the Linux kernel to a version containing commit e7c7b48a0fc5ed83baae400a1b15e33978c25d7f or later; apply distribution backports for affected stable trees.

How to confirm the fix worked

Verify the running kernel contains the referenced commit; attempt to set a zero-total mode via modetest or similar tools and confirm no panic occurs.

Typical attack path

1. Obtain local or remote access capable of submitting DRM modeset requests
2. Craft a mode structure where htotal or vtotal evaluates to zero after multiplication
3. Invoke drm_mode_vrefresh via ioctl or userspace display stack
4. Trigger kernel panic on divide-by-zero

How to detect it

Review kernel logs for divide-by-zero faults mentioning drm_mode_vrefresh; correlate with recent DRM mode changes or userspace graphics activity.

What your security team should do

• Prioritize kernel updates on all systems exposing DRM interfaces
• Monitor for kernel oops/panic logs related to drm_mode_vrefresh
• Restrict unprivileged access to graphics devices where feasible