The Linux kernel developers have switched links in the documentation over to HTTPS. The move aims to prevent man-in-the-middle attacks against kernel developers, luckily no such attacks have occurred.
Several commits have been made to the Linux kernel in recent days and weeks which switch links in the kernel’s documentation from HTTP to the more secure HTTPS protocol. According to commit logs made by Alexander Klimov, the switch to HTTPS should reduce the likelihood of man-in-the-middle attacks against kernel developers.