CVE-2026-23234: f2fs: fix to avoid UAF in f2fs_write_end_io()

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-04 · updated 2026-06-17
Weakness: CWE-416

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.

Affected products

Linux kernel: from 3.13 before 5.10.251; from 5.11 before 5.15.201; from 5.16 before 6.1.164; from 6.2 before 6.6.127; from 6.7 before 6.12.74; from 6.13 before 6.18.13 — fixed in 5.10.251, 5.15.201, 6.1.164, 6.12.74, 6.18.13, 6.19.3

How to fix

Upgrade to a fixed version: Linux kernel 5.10.251, 5.15.201, 6.1.164, 6.12.74. Check the vendor advisory for mitigations.

References

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