ioctl CAP_LINUX_IMMUTABLE is checked in the wrong namespace

[Andy Lutomirski]

On Tue, Apr 29, 2014 at 5:32 PM, Theodore Ts'o <tytso at mit.edu> wrote:
> 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 at init_user_ns is allowed to use mknod....

I haven't read the code, but I tried it the other day, and I got
-EPERM.  So we're okay for now.  (Well, other than the issue I just
sent to security at kernel.org, but that's not quite the same thing.)

--Andy