Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix potential deadlock in gc_merge path of f2fs_balance_fs()
When we mount device w/ gc_merge mount option, we may suffer below potential deadlock:
Kworker GC trehad Truncator
- f2fs_write_cache_pages
- f2fs_write_single_data_page
- f2fs_do_write_data_page
- folio_start_writeback — set writeback flag on folio
- f2fs_outplace_write_data : cached folio in internal bio cache
- f2fs_balance_fs
- wake_up(gc_thread) : wake up gc thread to run foreground GC
- finish_wait(fggc_wq) : wait on the waitqueue — wait on GC thread to finish the work
- truncate_inode_pages_range
- __filemap_get_folio(, FGP_LOCK) — lock folio
- truncate_inode_partial_folio
- folio_wait_writeback — wait on writeback being cleared
- do_garbage_collect
- move_data_page
- f2fs_get_lock_data_folio
- lock on folio — blocked on folio’s lock
In order to avoid such deadlock, let’s call below functions to commit cached bios in GC_MERGE path of f2fs_balance_fs() as the same as we did in NOGC_MERGE path.
- f2fs_submit_merged_write(sbi, DATA);
- f2fs_submit_all_merged_ipu_writes(sbi);
Details
- Affected product:
- Debian 10 ELS , Debian 11 ELS , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS , Ubuntu 20.04 ELS
- Affected packages:
- linux @ 5.10.259 (+4 more)