Zerocopy is a performance technique that reduces data movement by letting the kernel access user memory directly, often by pinning user pages instead of copying buffers into new kernel-owned memory. This can lower CPU use and latency in high-throughput networking or storage paths, because large payloads do not need repeated memcpy operations.
In cybersecurity, zerocopy matters because it changes memory lifetime and cleanup rules. Once pages are pinned, the kernel must release them in the correct order and keep accounting accurate. Bugs in setup, failure handling, or teardown can lead to stale references, leaked resources, or privilege boundaries being crossed. Defenders pay attention to zerocopy code because optimization paths are often less exercised than common slow paths, yet they still run inside the kernel. In real systems, secure use depends on careful validation, feature auditing, and patching of the kernel subsystems that implement these fast paths.