This call is what is used to implement `dmesg` to get kernel messages about the host. This can leak substantial information about the host. It is normally available to unprivileged users on the host, unless the sysctl `kernel.dmesg_restrict = 1` is set, but this is not set by standard on the majority of distributions. Blocking this to restrict leaks about the configuration seems correct. Relates to docker/docker#37897 "docker exposes dmesg to containers by default" See also https://googleprojectzero.blogspot.com/2018/09/a-cache-invalidation-bug-in-linux.html Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
contrib
The contrib directory contains packages that do not belong in the core containerd packages but still contribute to overall containerd usability.
Package such as Apparmor or Selinux are placed in contrib because they are platform dependent and often require higher level tools and profiles to work.
Packaging and other built tools can be added to contrib to aid in packaging containerd for various distributions.
Testing
Code in the contrib directory may or may not have been tested in the normal test pipeline for core components.