BPF Map Vulnerability in Linux Kernel

CVE-2025-21853

Summary

A design flaw in the Linux kernel related to BPF maps has been identified. The issue arises from holding the freeze_mutex during the entire mmap operation, which is unnecessary and can lead to potential deadlocks. By only holding the mutex during writeability checks and then proceeding with the mmap logic allows for better performance and reduces the risk of deadlocks. Proper handling of the 'write active' count ensures that any errors encountered during mmap can be managed effectively.

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