On Fri, Apr 5, 2019 at 12:36 PM Andrey Ignatov [off-list ref] wrote:

Containerized applications may run as root and it may create problems
for whole host. Specifically such applications may change a sysctl and
affect applications in other containers.

Furthermore in existing infrastructure it may not be possible to just
completely disable writing to sysctl, instead such a process should be
gradual with ability to log what sysctl are being changed by a
container, investigate, limit the set of writable sysctl to currently
used ones (so that new ones can not be changed) and eventually reduce
this set to zero.

Actual-root-in-a-container is pretty powerful. What about module
loading, or /dev files? Instead of sysctl-specific hooks, what about
VFS hooks, which would be able to cover all file-based APIs. This is
what, for example, Landlock was working on doing (also with eBPF).

-- 
Kees Cook