On Fri, Feb 28, 2020 at 4:09 PM James Bottomley
[off-list ref] wrote:

Containers are file based entities, so file descriptors are their most
natural thing and they have full ACL protection within the container
(can't open the file, can't then get the fd).  The other reason
container people like file descriptors (all the Xat system calls that
have been introduced) is that if we do actually need to break the
boundaries or privileges of the container, we can do so by getting the
orchestration system to pass in a fd the interior of the container
wouldn't have access to.

Yeah, agreed about the simplicity of fd based access.   Then again a
filesystem access would allow immediate access to all scripts,
languages, etc.  That, I think is a huge bonus compared to the
ioctl-like mess that the current proposal is, which would require
library, utility, language binding updates on all changes.  Ugh.

One way to resolve that is to have the mount information
magic-symlinked from /proc/PID/fdmount/FD directly to the mountinfo
dir, which would then have a link into the sbinfo dir.  With other
access denied to all except sysadmin.

Would that work?

Thanks,
Miklos