Bug 2516604 (CVE-2026-68459)

Summary: CVE-2026-68459 kernel: f2fs: fix potential deadlock in gc_merge path of f2fs_balance_fs()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's f2fs (Flash-Friendly File System) component. When a device is mounted with the `gc_merge` option, a specific interaction between kernel worker threads, the garbage collection thread, and the truncator can lead to a deadlock in the `f2fs_balance_fs()` function. This occurs when a memory page (folio) is locked and simultaneously awaited by multiple processes, resulting in a system-wide Denial of Service (DoS) condition.
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Description OSIDB Bzimport 2026-08-15 06:21:24 UTC 
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);
Comment 1 Keith Grant 2026-08-17 13:26:23 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081502-CVE-2026-68459-5502@gregkh/T