CVE-2024-43855

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

md: fix deadlock between mddev_suspend and flush bio

Deadlock occurs when mddev is being suspended while some flush bio is in

progress. It is a complex issue.

T1. the first flush is at the ending stage, it clears 'mddev->flush_bio'

and tries to submit data, but is blocked because mddev is suspended

by T4.

T2. the second flush sets 'mddev->flush_bio', and attempts to queue

md_submit_flush_data(), which is already running (T1) and won't

execute again if on the same CPU as T1.

T3. the third flush inc active_io and tries to flush, but is blocked because

'mddev->flush_bio' is not NULL (set by T2).

T4. mddev_suspend() is called and waits for active_io dec to 0 which is inc

by T3.

T1 T2 T3 T4

(flush 1) (flush 2) (third 3) (suspend)

md_submit_flush_data

mddev->flush_bio = NULL;

.

. md_flush_request

. mddev->flush_bio = bio

. queue submit_flushes

. .

. . m

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References