# CVE-2026-23234: f2fs: fix to avoid UAF in f2fs\_write\_end\_io()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-03-04 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 3.13

## Description

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to avoid UAF in f2fs_write_end_io() As syzbot reported an use-after-free issue in f2fs_write_end_io(). It is caused by below race condition: loop device umount - worker_thread - loop_process_work - do_req_filebacked - lo_rw_aio - lo_rw_aio_complete - blk_mq_end_request - blk_update_request - f2fs_write_end_io - dec_page_count - folio_end_writeback - kill_f2fs_super - kill_block_super - f2fs_put_super : free(sbi) : get_pages(, F2FS_WB_CP_DATA) accessed sbi which is freed In kill_f2fs_super(), we will drop all page caches of f2fs inodes before call free(sbi), it guarantee that all folios should end its writeback, so it should be safe to access sbi before last folio_end_writeback(). Let's relocate ckpt thread wakeup flow before folio_end_writeback() to resolve this issue.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
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## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/0fb58aff0dafd6837cc91f4154f3ed6e020358fa
- https://git.kernel.org/stable/c/2f67ff1e15a8a4d0e4ffc6564ab20d03d7398fe9
- https://git.kernel.org/stable/c/505e1c0530db6152cab3feef8e3e4da3d3e358c9
- https://git.kernel.org/stable/c/acc2c97fc0005846e5cf11b5ba3189fef130c9b3
- https://git.kernel.org/stable/c/cf4a9e1bc8129eb63fda5f8bdcd8d87f0bd76f42
- https://git.kernel.org/stable/c/995030be4ce6338c6ff814583c14166446a64008
- https://git.kernel.org/stable/c/a42f99be8a16b32a0bb91bb6dda212a6ad61be5d
- https://git.kernel.org/stable/c/ce2739e482bce8d2c014d76c4531c877f382aa54

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