CVE-2025-21853
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk11th percentile - higher than 11% of all known CVEs
Summary
In the Linux kernel, a vulnerability in BPF was found where the freeze_mutex was held during the entire mmap operation, potentially leading to deadlocks. The fix reduces the lock hold time to only the necessary write permission checks.
Risk Assessment
This vulnerability could allow an attacker to cause a system deadlock when attempting to freeze a BPF map while simultaneously mapping its memory, resulting in a denial of service (DoS).
Recommendation
Immediately update the Linux kernel to a version containing the fix (commit that removes holding freeze_mutex during mmap).
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: bpf: avoid holding freeze_mutex during mmap operation We use map->freeze_mutex to prevent races between map_freeze() and memory mapping BPF map contents with writable permissions. The way we naively do this means we'll hold freeze_mutex for entire duration of all the mm and VMA manipulations, which is completely unnecessary. This can potentially also lead to deadlocks, as reported by syzbot in [0]. So, instead, hold freeze_mutex only during writeability checks, bump (proactively) "write active" count for the map, unlock the mutex and proceed with mmap logic. And only if something went wrong during mmap logic, then undo that "write active" counter increment. [0] https://lore.kernel.org/bpf/[email protected]/