Executive brief
A vulnerability was identified in the Linux kernel's F2FS file system, which is commonly used on flash-based storage devices like smartphones and SSDs. A flaw in how the system manages file data 'extents' could lead to unpredictable system behavior or potential security breaches. If exploited, a local attacker could potentially gain unauthorized access to sensitive information or cause a system crash.
Technical details
A use-of-uninitialized-value vulnerability exists in the Linux kernel F2FS file system within the `__is_extent_mergeable()` and `__is_back_mergeable()` functions. The root cause is that `get_read_extent_info()` only initializes a subset of fields (`fofs`, `blk`, `len`) in `struct extent_info`, leaving other fields containing junk data from the stack. When these uninitialized fields are accessed during extent merging operations, it leads to undefined behavior. This is a local vulnerability (CWE-908) that could be exploited by a local user to cause a kernel crash or potentially leak sensitive kernel memory. The issue has been resolved by zero-initializing the `extent_info` structure in `fs/f2fs/extent_cache.c`.
Affected products
- Linux Linux Kernel 5.15 to 6.16.1
Timeline
- 2025-06-30: patched: Initial patch committed to mainline kernel tree
- 2025-08-19: advisory: CVE-2025-38579 published
References
- https://git.kernel.org/stable/c/01b6f5955e0008af6bc3a181310d2744bb349800
- https://git.kernel.org/stable/c/08e8ab00a6d20d5544c932ee85a297d833895141
- https://git.kernel.org/stable/c/154467f4ad033473e5c903a03e7b9bca7df9a0fa
- https://git.kernel.org/stable/c/44a79437309e0ee2276ac17aaedc71253af253a8
- https://git.kernel.org/stable/c/cc1615d5aba4f396cf412579928539a2b124c8a0
- https://git.kernel.org/stable/c/dabfa3952c8e6bfe6414dbf32e8b6c5f349dc898
- https://git.kernel.org/stable/c/e68b751ec2b15d866967812c57cfdfc1eba6a269