CVE-2025-21853

Summary

CVE-2025-21853 is a vulnerability affecting the Linux kernel. This issue involves the BPF (Berkeley Packet Filter) subsystem, where holding the freeze_mutex mutex during mmap (memory mapping) operations is unnecessary and can potentially lead to deadlocks. The vulnerability was reported by syzbot, and the issue has been resolved by holding freeze_mutex only during writeability checks, proactively bumping the "write active" counter for the map, and unlocking the mutex before proceeding with the mmap logic. If any issues arise during the mmap logic, the "write active" counter increment will be undone.

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