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

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-08-19 · updated 2026-07-30
Weakness: CWE-908

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.

Affected products

Debian Linux: 11.0
Linux kernel: from 5.15 before 5.15.190; from 5.16 before 6.1.148; from 6.2 before 6.6.102; from 6.7 before 6.12.42; from 6.13 before 6.15.10; from 6.16 before 6.16.1 — fixed in 5.15.190, 6.1.148, 6.12.42, 6.15.10, 6.16.1, 6.6.102

How to fix

Upgrade to a fixed version: Linux kernel 5.15.190, 6.1.148, 6.12.42, 6.15.10. Check the vendor advisory for mitigations.

References

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