CVE-2024-34027 – Resolving Linux Kernel Vulnerability, f2fs: compress, Covering {reserve,release}_compress_blocks() w/ cp_rwsem Lock

A new vulnerability, registered as CVE-2024-34027, was discovered in the Linux kernel that affects the f2fs (Flash-Friendly File System) component. This vulnerability could potentially corrupt the file system metadata in specific scenarios. In this post, we will dive deep into the details of this vulnerability, provide the code snippets and the links to the original references, and discuss the implications of this vulnerability.

CVE-2024-34027 – The Vulnerability Explained

In the Linux kernel, the f2fs: compress component has a specific vulnerability that requires addressing in order to prevent possible corruption of the filesystem metadata. The primary issue revolves around the need to cover the {reserve,release}_compress_blocks() functions with the cp_rwsem lock. Without properly addressing this, it could ultimately lead to races with checkpoint, which might cause the filesystem metadata, including blkaddr in dnode, inode fields, and .total_valid_block_count, to become corrupted after an SPO (Sudden Power Off) case.

Here is a snippet of the code fix to address the vulnerability in the Linux kernel

-   if (do_claim_space(inode, cc))
-       goto release_blocks;
+  down_write(&sbi->cp_rwsem);
+       if (do_claim_space(inode, cc))
+               goto release_blocks;
+   up_write(&sbi->cp_rwsem);

Original References and Links

For more information, check out the original report and patch details submitted to the Linux kernel mailing list:

- Report: Link to mailing list report
- Patch: Link to mailing list patch

Exploit Details

The exploit's main concern is the possible corruption of the filesystem metadata due to the failure to cover the {reserve,release}_compress_blocks() functions with the cp_rwsem lock. An attacker might make use of this vulnerability to purposely cause a race with checkpoint, ultimately leading to corrupted filesystem metadata in specific cases. Although this vulnerability might not have a direct security impact, it can cause data loss and system instability.

Conclusion

CVE-2024-34027 is an important vulnerability in the Linux kernel that could lead to corrupted filesystem metadata if not addressed. The patch has been submitted to the Linux kernel mailing list and should be applied in order to prevent possible unauthorized exploitation of this vulnerability. It is important for system administrators and developers to keep their environments up to date to avoid such issues and ensure the overall security and stability of their systems.

In conclusion, understanding the details of the CVE-2024-34027 vulnerability, including its scope, the code snippet of the fix, and the original references, can help provide a deeper understanding of the issue and aid in keeping the Linux kernel more secure.

Timeline

Published on: 06/24/2024 14:15:11 UTC
Last modified on: 07/15/2024 06:46:46 UTC