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CVE-2025-22123

Description

In the Linux kernel, the following vulnerability has been resolved:f2fs: fix to avoid accessing uninitialized cursegsyzbot reports a f2fs bug as below:F2FS-fs (loop3): Stopped filesystem due to reason: 7kworker/u8:7: attempt to access beyond end of deviceBUG: unable to handle page fault for address: ffffed1604ea3dfaRIP: 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 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:244Commit 8b10d3653735 ("f2fs: introduce FAULT_NO_SEGMENT") allows to triggerno free segment fault in allocator, then it will update curseg->segno toNULL_SEGNO, though, CP_ERROR_FLAG has been set, f2fs_write_inode() missedto check the flag, and access invalid curseg->segno directly in below callpath, 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->segnoTo avoid this issue, let's:- check CP_ERROR_FLAG flag in prior to f2fs_is_checkpoint_ready() inf2fs_write_inode().- in has_curseg_enough_space(), save curseg->segno into a temp variable,and verify its validation before use.

POC

Reference

No PoCs from references.

Github

- https://github.com/fkie-cad/nvd-json-data-feeds