CVE-2023-54068

Summary

In the Linux kernel, the following vulnerability has been resolved:

f2fs: compress: fix to call f2fs_wait_on_page_writeback() in f2fs_write_raw_pages()

BUG_ON() will be triggered when writing files concurrently, because the same page is writtenback multiple times.

1597 void folio_end_writeback(struct folio *folio) 1598 { …… 1618 if (!__folio_end_writeback(folio)) 1619 BUG(); …… 1625 }

kernel BUG at mm/filemap.c:1619! Call Trace: <TASK> f2fs_write_end_io+0x1a0/0x370 blk_update_request+0x6c/0x410 blk_mq_end_request+0x15/0x130 blk_complete_reqs+0x3c/0x50 __do_softirq+0xb8/0x29b ? sort_range+0x20/0x20 run_ksoftirqd+0x19/0x20 smpboot_thread_fn+0x10b/0x1d0 kthread+0xde/0x110 ? kthread_complete_and_exit+0x20/0x20 ret_from_fork+0x22/0x30 </TASK>

Below is the concurrency scenario:

[Process A] [Process B] [Process C] f2fs_write_raw_pages()

• redirty_page_for_writepage()

• unlock page() f2fs_do_write_data_page() - lock_page() - clear_page_dirty_for_io() - set_page_writeback() [1st writeback] ….. - unlock page()

  				generic_perform_write()
  				  - f2fs_write_begin()
  				    - wait_for_stable_page()
  
  				  - f2fs_write_end()
  				    - set_page_dirty()
  

• lock_page()

  • f2fs_do_write_data_page()
    • set_page_writeback() [2st writeback]

This problem was introduced by the previous commit 7377e853967b ("f2fs: compress: fix potential deadlock of compress file"). All pagelocks were released in f2fs_write_raw_pages(), but whether the page was in the writeback state was ignored in the subsequent writing process. Let's fix it by waiting for the page to writeback before writing.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/a8226a45b2a9ce83ba7a167a387a00fecc319e71
• https://git.kernel.org/stable/c/169134da419cb8ffbe3b0743bc24573e16952ea9
• https://git.kernel.org/stable/c/6604df2a9d07ba8f8fb1ac14046c2c83776faa4f
• https://git.kernel.org/stable/c/9940877c4fe752923a53f0f7372f2f152b6eccf0
• https://git.kernel.org/stable/c/ad31eed06c3b4d63b2d38322a271d4009aee4bb3
• https://git.kernel.org/stable/c/babedcbac164cec970872b8097401ca913a80e61

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