# CVE-2026-46280: lib: test_hmm: evict device pages on file close to avoid use-after-free

CVE-2026-46280 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-46280, released June 24, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-46280
- Priority: High
- CVSS: 7.8 (Moderate)
- EPSS: 0.0013
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 8, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-46280

## Description

In the Linux kernel, the following vulnerability has been resolved:  lib: test_hmm: evict device pages on file close to avoid use-after-free  Patch series "Minor hmm_test fixes and cleanups".  Two bugfixes a cleanup for the HMM kernel selftests.  These were mostly reported by Zenghui Yu with special thanks to Lorenzo for analysing and pointing out the problems.   This patch (of 3):  When dmirror_fops_release() is called it frees the dmirror struct but doesn't migrate device private pages back to system memory first.  This leaves those pages with a dangling zone_device_data pointer to the freed dmirror.  If a subsequent fault occurs on those pages (eg.  during coredump) the dmirror_devmem_fault() callback dereferences the stale pointer causing a kernel panic.  This was reported [1] when running mm/ksft_hmm.sh on arm64, where a test failure triggered SIGABRT and the resulting coredump walked the VMAs faulting in the stale device private pages.  Fix this by calling dmirror_device_evict_chunk() for each devmem chunk in dmirror_fops_release() to migrate all device private pages back to system memory before freeing the dmirror struct.  The function is moved earlier in the file to avoid a forward declaration.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.176-1 | [DEBIAN-CVE-2026-46280](https://patchblox.com/security/data/fix/linux/debian-cve-2026-46280.md) | Jun 24, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.86-1 | [DEBIAN-CVE-2026-46280](https://patchblox.com/security/data/fix/linux/debian-cve-2026-46280.md) | Jun 24, 2026 |
| Linux | linux Debian 14 | 7.0.4-1 | [DEBIAN-CVE-2026-46280](https://patchblox.com/security/data/fix/linux/debian-cve-2026-46280.md) | Jun 24, 2026 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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