CVE-2023-54068 in Linux
Summary
by MITRE • 12/24/2025
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.
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Analysis
by VulDB Data Team • 01/02/2026
The vulnerability CVE-2023-54068 resides within the Linux kernel's f2fs (Flash-Friendly File System) implementation, specifically affecting the compression functionality. This issue manifests as a kernel BUG triggered by concurrent file writing operations, where the same page undergoes multiple writeback processes simultaneously. The root cause lies in the improper handling of page writeback states during concurrent access scenarios, leading to a violation of kernel assumptions that results in system instability.
The technical flaw occurs in the f2fs_write_raw_pages() function where the kernel's BUG_ON() macro is invoked due to inconsistent page state management. When multiple processes attempt to write to the same page concurrently, the page can be marked for writeback multiple times before the previous writeback operation completes. This concurrency scenario is particularly problematic in the context of compressed file operations, where the page state transitions occur more frequently and with greater complexity. The issue is further exacerbated by the fact that the previous commit 7377e853967b, which was intended to fix a deadlock in compress file operations, inadvertently introduced this page state management bug by releasing all pagelocks without properly accounting for existing writeback states.
The operational impact of this vulnerability is significant as it can lead to kernel panics and system crashes when concurrent file writing operations occur in environments using f2fs with compression enabled. The specific call trace demonstrates the path through which the bug manifests, starting from f2fs_write_end_io through various kernel subsystems including blk_update_request and ending at the BUG at mm/filemap.c:1619. This vulnerability affects systems where f2fs is used as the primary filesystem, particularly those handling concurrent I/O operations on compressed files. The risk is elevated in server environments or systems with multiple concurrent users performing file operations, as the probability of triggering this race condition increases with concurrent access patterns.
The mitigation strategy involves implementing proper synchronization mechanisms to ensure that pages are not written back multiple times concurrently. The fix requires calling f2fs_wait_on_page_writeback() before proceeding with page writeback operations in f2fs_write_raw_pages(). This approach aligns with the principle of preventing race conditions and maintaining consistent page states throughout the writeback process. From a cybersecurity perspective, this vulnerability represents a potential denial-of-service vector that could be exploited by malicious actors to destabilize systems running f2fs with compression. The issue maps to CWE-362 (Concurrent Execution using Shared Resource with Unprotected Race Condition) and potentially CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) in the CWE catalog. From an ATT&CK framework perspective, this vulnerability could be leveraged in a denial-of-service attack (T1499) or potentially as a stepping stone for more sophisticated attacks if exploited in a controlled environment, though it primarily serves as a system stability concern rather than a direct privilege escalation vector.