CVE-2023-52848 in Linux
Summary
by MITRE • 05/21/2024
In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix to drop meta_inode's page cache in f2fs_put_super()
syzbot reports a kernel bug as below:
F2FS-fs (loop1): detect filesystem reference count leak during umount, type: 10, count: 1 kernel BUG at fs/f2fs/super.c:1639! CPU: 0 PID: 15451 Comm: syz-executor.1 Not tainted 6.5.0-syzkaller-09338-ge0152e7481c6 #0 RIP: 0010:f2fs_put_super+0xce1/0xed0 fs/f2fs/super.c:1639 Call Trace: generic_shutdown_super+0x161/0x3c0 fs/super.c:693 kill_block_super+0x3b/0x70 fs/super.c:1646 kill_f2fs_super+0x2b7/0x3d0 fs/f2fs/super.c:4879 deactivate_locked_super+0x9a/0x170 fs/super.c:481 deactivate_super+0xde/0x100 fs/super.c:514 cleanup_mnt+0x222/0x3d0 fs/namespace.c:1254 task_work_run+0x14d/0x240 kernel/task_work.c:179 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
exit_to_user_mode_prepare+0x210/0x240 kernel/entry/common.c:204 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
syscall_exit_to_user_mode+0x1d/0x60 kernel/entry/common.c:296 do_syscall_64+0x44/0xb0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x63/0xcd
In f2fs_put_super(), it tries to do sanity check on dirty and IO reference count of f2fs, once there is any reference count leak, it will trigger panic.
The root case is, during f2fs_put_super(), if there is any IO error in f2fs_wait_on_all_pages(), we missed to truncate meta_inode's page cache later, result in panic, fix this case.
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Analysis
by VulDB Data Team • 12/31/2024
The vulnerability described in CVE-2023-52848 affects the F2FS (Flash-Friendly File System) implementation within the Linux kernel, specifically during the unmount process. This issue manifests as a filesystem reference count leak that leads to a kernel panic, demonstrating a critical flaw in the cleanup procedures for F2FS superblock handling. The problem occurs in the f2fs_put_super() function where the kernel attempts to perform sanity checks on dirty and I/O reference counts. When an I/O error occurs during f2fs_wait_on_all_pages() execution, the system fails to properly truncate the meta_inode's page cache, resulting in an inconsistent state that triggers a kernel panic at line 1639 of fs/f2fs/super.c. This vulnerability represents a classic case of improper error handling in resource cleanup operations, where failure to execute cleanup steps under error conditions leads to system instability.
The technical flaw stems from inadequate error handling in the F2FS unmount sequence, specifically when dealing with I/O operations that may fail during page cache management. The kernel's f2fs_put_super() function performs essential cleanup duties including checking reference counts and managing page cache for meta_inodes. When f2fs_wait_on_all_pages() encounters an I/O error, the subsequent code path fails to properly truncate the meta_inode's page cache, leaving the system in an inconsistent state. This error condition causes the kernel to trigger a panic as a safety measure, preventing further operation on a potentially corrupted filesystem state. The vulnerability demonstrates a failure in the principle of defensive programming where error conditions should be handled gracefully rather than causing system-wide crashes. According to CWE-459, this represents a partial cleanup vulnerability where resources are not properly released, and aligns with ATT&CK technique T1489 which covers system shutdown/reboot to disrupt services.
The operational impact of CVE-2023-52848 extends beyond simple system crashes, as it can lead to complete system instability during filesystem unmount operations. This vulnerability particularly affects systems using F2FS filesystems that experience I/O errors during shutdown or unmount procedures, potentially causing denial of service conditions for applications relying on these filesystems. The panic occurs during the generic_shutdown_super() sequence, which is part of the standard filesystem unmount process, making this issue relevant to any system utilizing F2FS that may encounter I/O failures. The vulnerability affects kernel versions including 6.5.0 and potentially earlier versions that implement the problematic f2fs_put_super() function, with the specific code path being triggered by the interaction between f2fs_wait_on_all_pages() and meta_inode page cache management. System administrators and developers should be aware that this vulnerability can be triggered during normal unmount operations when I/O errors occur, potentially affecting embedded systems, mobile devices, or any platform using F2FS that may experience storage layer issues.
Mitigation strategies for CVE-2023-52848 focus on ensuring proper error handling in the F2FS unmount process, particularly when I/O operations fail during page cache management. The fix requires implementing proper cleanup procedures that ensure meta_inode page cache truncation regardless of whether I/O operations succeed or fail during f2fs_wait_on_all_pages(). System administrators should ensure their kernels are updated to versions containing the patched f2fs_put_super() implementation that correctly handles error conditions in the page cache management sequence. Monitoring for I/O errors during filesystem operations becomes crucial, as these errors trigger the vulnerability path. Additionally, implementing robust filesystem health checks and ensuring adequate storage layer reliability can reduce the likelihood of triggering this vulnerability. The fix aligns with security best practices by ensuring that all resource cleanup paths properly execute even under error conditions, preventing resource leaks that could lead to system instability. Organizations should prioritize kernel updates to address this vulnerability, particularly in environments where F2FS filesystems are actively used and where system reliability is critical.