CVE-2026-97534
Received Received - Intake

F2FS Filesystem Free Section Accounting Error in Linux Kernel

Publication date: 2026-09-25

Last updated on: 2026-09-25

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: f2fs: accurately adjust free_sections during free_segment_range In free_segment_range(), MAIN_SECS(sbi) is temporarily reduced by `secs` to restrict block allocation to the safe remaining main area while valid blocks in the truncated range are evacuated by GC. However, FREE_I(sbi)->free_sections tracks the total number of free sections across the whole filesystem. If any sections within the truncated range were already free upon entering free_segment_range(), failing to deduct them from free_sections causes the filesystem to overestimate available free sections in the active, reduced main area. This leads to inconsistent free section accounting during GC data migration and can trigger unexpected allocation failures or assertion errors when space is tight. Fix this by calculating the number of already-free sections in the truncated range, deducting them from free_sections upon entering free_segment_range(), and restoring them on exit.

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Meta Information

Published
2026-09-25
Last Modified
2026-09-25
Generated
2026-09-25
AI Q&A
2026-09-25
EPSS Evaluated
N/A
NVD
CVE-2026-97534
EUVD
EUVD-2026-86842

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel's F2FS filesystem involves incorrect accounting of free sections during segment range operations. When truncating a file, the system temporarily reduces the main area for safe block allocation but fails to adjust the free_sections counter properly. If sections in the truncated range were already free, the counter overestimates available space, leading to inconsistent accounting during garbage collection and potential allocation failures or errors.

Detection Guidance

This vulnerability is specific to the Linux kernel's F2FS filesystem implementation and does not have direct network detection methods. Detection involves checking kernel logs for filesystem errors or assertion failures related to F2FS operations. Monitor logs with commands like dmesg | grep f2fs or journalctl -k | grep f2fs. If you suspect exploitation, verify filesystem consistency using fsck.f2fs /dev/your_device.

Impact Analysis

This vulnerability could cause filesystem corruption or data loss if the kernel incorrectly handles space allocation during file operations. Users might experience crashes, failed writes, or filesystem errors when disk space is low, particularly during file truncation or garbage collection.

Mitigation Strategies

Immediate mitigation requires updating the Linux kernel to a patched version that includes the fix for this F2FS vulnerability. Check your distribution's security updates or kernel release notes for the corrected version. If updating is not immediately possible, avoid filesystem operations that could trigger the vulnerable code path, such as resizing or truncating F2FS partitions.

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