Writeback Vulnerability in Btrfs RAID5 Metadata Handling for Linux Kernel

CVE-2025-40303

What is CVE-2025-40303?

A vulnerability in the Btrfs filesystem affects RAID5 metadata handling in the Linux kernel. When the filesystem encounters an error, it enters an error state where new transactions are disallowed. However, certain dirty metadata modifications may still reside in the page cache, leading to potential data corruption. If these are not handled correctly during the writeback process, it can result in a use-after-free condition when invoking write operations. This issue occurs without code modification, specifically when running workloads that trigger worker tasks in the kernel. The vulnerability has been addressed by implementing a special condition in the writeback process, ensuring that if the filesystem is flagged with errors, any pending metadata writes are marked as failures to prevent further corruption.

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