sendfile

This article explains how Go's io.Copy automatically uses sendfile and splice for zero-copy file transfers over TCP, and demonstrates how wrapping a file in a plain io.Reader—e.g., for logging—quietly disables this optimization, causing a significant performance drop. Benchmarks and strace output illustrate the impact.

A critical local privilege escalation vulnerability in FreeBSD (CVE-2026-45257) allows an unprivileged user to write arbitrary data into the page cache of any readable file, bypassing file permissions and flags, leading to full root compromise. The bug affects default installations of FreeBSD 13.0 and later via unsafe composition of sendfile, KTLS, and in-kernel AES-GCM decryption.