CVE-2025-22123 f2fs: fix to avoid accessing uninitialized curseg
A local attacker can trigger a kernel panic in the f2fs filesystem by accessing an uninitialized segment structure, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-22123?
CVE-2025-22123 is a medium-severity vulnerability in Linux kernel, published on 16 Apr 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix to avoid accessing uninitialized curseg
syzbot reports a f2fs bug as below:
F2FS-fs (loop3): Stopped filesystem due to reason: 7 kworker/u8:7: attempt to access beyond end of device BUG: unable to handle page fault for address: ffffed1604ea3dfa RIP: 0010:get_ckpt_valid_blocks fs/f2fs/segment.h:361 [inline] RIP: 0010:has_curseg_enough_space fs/f2fs/segment.h:570 [inline] RIP: 0010:__get_secs_required fs/f2fs/segment.h:620 [inline] RIP: 0010:has_not_enough_free_secs fs/f2fs/segment.h:633 [inline] RIP: 0010:has_enough_free_secs+0x575/0x1660 fs/f2fs/segment.h:649 <TASK> f2fs_is_checkpoint_ready fs/f2fs/segment.h:671 [inline] f2fs_write_inode+0x425/0x540 fs/f2fs/inode.c:791 write_inode fs/fs-writeback.c:1525 [inline] __writeback_single_inode+0x708/0x10d0 fs/fs-writeback.c:1745 writeback_sb_inodes+0x820/0x1360 fs/fs-writeback.c:1976 wb_writeback+0x413/0xb80 fs/fs-writeback.c:2156 wb_do_writeback fs/fs-writeback.c:2303 [inline] wb_workfn+0x410/0x1080 fs/fs-writeback.c:2343 process_one_work kernel/workqueue.c:3236 [inline] process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317 worker_thread+0x870/0xd30 kernel/workqueue.c:3398 kthread+0x7a9/0x920 kernel/kthread.c:464 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
Commit 8b10d3653735 ("f2fs: introduce FAULT_NO_SEGMENT") allows to trigger no free segment fault in allocator, then it will update curseg->segno to NULL_SEGNO, though, CP_ERROR_FLAG has been set, f2fs_write_inode() missed to check the flag, and access invalid curseg->segno directly in below call path, then resulting in panic:
- f2fs_write_inode - f2fs_is_checkpoint_ready - has_enough_free_secs - has_not_enough_free_secs - __get_secs_required - has_curseg_enough_space - get_ckpt_valid_blocks : access invalid curseg->segno
To avoid this issue, let's: - check CP_ERROR_FLAG flag in prior to f2fs_is_checkpoint_ready() in f2fs_write_inode(). - in has_curseg_enough_space(), save curseg->segno into a temp variable, and verify its validation before use.
Weakness: CWE-908
Which versions are affected by CVE-2025-22123?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-22123?
Apply the vendor's patch.
Is CVE-2025-22123 being exploited?
There is no known exploitation of CVE-2025-22123 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-22123, DEBIAN-CVE-2025-22123, GHSA-fq4p-236v-8g34, UBUNTU-CVE-2025-22123.