Bug 2389488 (CVE-2025-38579)

Summary: CVE-2025-38579 kernel: f2fs: fix KMSAN uninit-value in extent_info usage
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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OS: Linux   
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Description OSIDB Bzimport 2025-08-19 18:03:39 UTC 
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.
Comment 1 Keith Grant 2025-08-20 17:28:40 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025081913-CVE-2025-38579-db94@gregkh/T