# CVE-2025-38579: f2fs: fix KMSAN uninit-value in extent_info usage

CVE-2025-38579 is fixed in linux on 1 platform, first by DEBIAN-CVE-2025-38579, released August 19, 2025. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2025-38579
- Priority: High
- CVSS: 7.8 (high)
- EPSS: 0.0018
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 19, 2025
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-38579

## Description

In the Linux kernel, the following vulnerability has been resolved:  f2fs: fix KMSAN uninit-value in extent_info usage  KMSAN reported a use of uninitialized value in `__is_extent_mergeable()`  and `__is_back_mergeable()` via the read extent tree path.  The root cause is that `get_read_extent_info()` only initializes three fields (`fofs`, `blk`, `len`) of `struct extent_info`, leaving the remaining fields uninitialized. This leads to undefined behavior when those fields are accessed later, especially during extent merging.  Fix it by zero-initializing the `extent_info` struct before population.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.148-1 | [DEBIAN-CVE-2025-38579](https://patchblox.com/security/data/fix/linux/debian-cve-2025-38579.md) | Aug 19, 2025 |
| Linux | linux Debian 13.5 (trixie) | 6.12.43-1 | [DEBIAN-CVE-2025-38579](https://patchblox.com/security/data/fix/linux/debian-cve-2025-38579.md) | Aug 19, 2025 |
| Linux | linux Debian 14 | 6.16.3-1 | [DEBIAN-CVE-2025-38579](https://patchblox.com/security/data/fix/linux/debian-cve-2025-38579.md) | Aug 19, 2025 |

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