CVE-2024-43855md: fix deadlock between mddev_suspend and flush bio
- 5.5MediumCVSS base score
- 0.21%Exploitation in 30 daysEPSS · top 89% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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 . . . . md_handle_request . . active_io + 1 . . md_flush_request . . wait !mddev->flush_bio . . . . mddev_suspend . . wait !active_io . . . submit_flushes . queue_work md_submit_flush_data . //md_submit_flush_data is already running (T1) . md_handle_request wait resume The root issue is non-atomic inc/dec of active_io during flush process. active_io is dec before md_submit_flush_data is queued, and inc soon after md_submit_flush_data() run. md_flush_request active_io + 1 submit_flushes active_io - 1 md_submit_flush_data md_handle_request active_io + 1 make_request active_io - 1 If active_io is dec after md_handle_request() instead of within submit_flushes(), make_request() can be called directly intead of md_handle_request() in md_submit_flush_data(), and active_io will only inc and dec once in the whole flush process. Deadlock will be fixed. Additionally, the only difference between fixing the issue and before is that there is no return error handling of make_request(). But after previous patch cleaned md_write_start(), make_requst() only return error in raid5_make_request() by dm-raid, see commit 41425f96d7aa ("dm-raid456, md/raid456: fix a deadlock for dm-raid456 while io concurrent with reshape)". Since dm always splits data and flush operation into two separate io, io size of flush submitted by dm always is 0, make_request() will not be called in md_submit_flush_data(). To prevent future modifications from introducing issues, add WARN_ON to ensure make_request() no error is returned in this context.
Timeline
ID reserved
By Linux
Published
- 21 months later
· 21 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.1 | Medium5.5 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.21% · top 89% of all CVEs (15 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.
Affected products
- affected f9f2d957a8ea93c73182aebf7de30935a58c027d – < 32226070813140234b6c507084738e8e8385c5c6
- affected 530cec617f5a8ba6f26bcbf0d64d75c951d17730 – < 2d0738a8322bf4e5bfe693d16b3111928a9ccfbf
- affected fa2bbff7b0b4e211fec5e5686ef96350690597b5 – < ca963eefbc3331222b6121baa696d49ba2008811
- affected fa2bbff7b0b4e211fec5e5686ef96350690597b5 – < 611d5cbc0b35a752e657a83eebadf40d814d006b
- affected c4c2345214b66e2505a26fd2ea58839dd7a1d48d
- affected 6.1.75 – < 6.1.103
- affected 6.6.14 – < 6.6.44
- affected 6.7.2 – < 6.8
- affected 6.8
- unaffected < 6.8
- unaffected 6.1.103 – ≤ 6.1.*
- unaffected 6.6.44 – ≤ 6.6.*
- unaffected 6.10.3 – ≤ 6.10.*
- unaffected 6.11 – ≤ *
References
References5
- https://git.kernel.org/stable/c/32226070813140234b6c507084738e8e8385c5c6 (opens in a new tab)
- https://git.kernel.org/stable/c/2d0738a8322bf4e5bfe693d16b3111928a9ccfbf (opens in a new tab)
- https://git.kernel.org/stable/c/ca963eefbc3331222b6121baa696d49ba2008811 (opens in a new tab)
- https://git.kernel.org/stable/c/611d5cbc0b35a752e657a83eebadf40d814d006b (opens in a new tab)
- https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2024-40505 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2024-43855)Record last updated .