Executive brief
F2FS is a flash-friendly file system used in the Linux kernel to optimize storage on devices with limited resources. A race condition during directory move operations can cause file system corruption if a directory is converted from inline format to normal format concurrently, potentially leading to data loss or system instability.
Technical details
This vulnerability is a race condition in the F2FS `f2fs_rename()` function that mirrors a similar issue fixed in ext4 (commit 0813299c586b). The vulnerability occurs when moving a directory: if the source directory is converted from inline directory format to normal format while the rename operation is in progress, it can cause file system corruption or crashes. The fix adds inode-level locking (I_MUTEX_NONDIR2) around the critical section of the rename operation when the source is a directory, preventing concurrent format conversion. The vulnerability requires local file system access and can be triggered via filesystem operations like `mv` commands. Patches are available in Linux kernel stable trees from version 4.0 onwards.
Affected products
- Linux Linux kernel Affects multiple versions; fix available in stable branches from 4.0.y onwards
Timeline
- 2023-04-06: disclosed
- 2023-05-17: patched
- 2025-12-30: advisory