Re: ioctl CAP_LINUX_IMMUTABLE is checked in the wrong namespace

Serge Hallyn
2014-04-30T00:40:07Z

Quoting Theodore Ts'o (tytso@mit.edu):
> On Wed, Apr 30, 2014 at 12:16:41AM +0000, Serge Hallyn wrote:
> > I forget the details, but there was another case where I wanted to
> > have the userns which 'owns' the whole fs available. I guess we'd
> > have to check against that instead of using inode_capable.
>
> Yes, that sounds right.
>
> And *please* tell me that that under no circumstances can anyone other
> than root@init_user_ns is allowed to use mknod....

That's the case. We've considered making exceptions for things like
/dev/null, but in practice bind-mounting devices from the host has
worked out just fine.