CVE-2024-36917

What it actually does

Missing bounds check allows integer overflow when computing start + len in blk_ioctl_discard, permitting crafted discard parameters to trigger a hung task.

Why it matters to the business

Unpatched Linux systems may experience denial-of-service conditions during routine storage discard operations, increasing downtime risk for servers and devices that rely on the kernel block layer.

How an attack unfolds

An attacker with local access crafts a discard ioctl request using specially chosen large start and len values that overflow when added, causing the kernel to enter an unhandled state and hang the task.

How to fix it

Upgrade the Linux kernel to a version containing commit 8a26198186e97ee5fc4b42fde82629cff8c75cd6 or later that adds the overflow validation in blk_ioctl_discard.

How to confirm the fix worked

Confirm the presence of the overflow check on start + len inside blk_ioctl_discard and verify the running kernel reports the fixed commit or a later stable release.

Typical attack path

1. Obtain local access on a Linux system
2. Locate or create a block device supporting discard ioctls
3. Invoke the discard ioctl with overflow-inducing start and len parameters
4. Trigger the missing validation path leading to hung task

How to detect it

Review system logs for hung-task warnings referencing blk_ioctl_discard or discard ioctls, and inspect audit records of ioctl calls targeting block devices for unusually large start or len values.

What your security team should do

• Apply the kernel patch containing commit 8a26198186e97ee5fc4b42fde82629cff8c75cd6 as soon as a distribution package is available
• Prioritize systems that expose block devices to untrusted local users
• Monitor for distribution kernel updates and test in staging environments before broad deployment