Re: [patch 07/10] unprivileged mounts: add sysctl tunable for "safe" property

[Miklos Szeredi <miklos@szeredi.hu>]

> > Maybe sysctls just need to check capabilities, instead of uids.  I
> > think that would make a lot of sense anyway.
> 
> Would it be as simple as tagging the inodes with capability sets?  One
> set for writing, or one each for reading and writing?

Yes, or something even simpler, like mapping the owner permission bits
to CAP_SYS_ADMIN.  There seem to be very few different permissions
under /proc/sys:

--w-------
-r--r--r--
-rw-------
-rw-r--r--

As long as the group and other bits are always the same, and we accept
that the owner bits really mean CAP_SYS_ADMIN and not something else,
then the permission check would not need to look at uids or gids at
all.

Miklos