Re: [PATCH 14/19] fs: Permit FIBMAP for users with CAP_SYS_RAWIO in s_user_ns

Serge E. Hallyn
2015-12-04T23:43:49Z

On Fri, Dec 04, 2015 at 06:11:52PM -0500, Theodore Ts'o wrote:
> On Fri, Dec 04, 2015 at 02:45:32PM -0600, Seth Forshee wrote:
> > On Fri, Dec 04, 2015 at 02:07:36PM -0600, Serge E. Hallyn wrote:
> > > Heh, I was looking over http://www.gossamer-threads.com/lists/linux/kernel/103611
> > > a little while ago :) The same question was asked 16 years ago. Apparently
> > > the answer then was that it was easier than fixing the code.
> >
> > So it seems then that either it still isn't safe and so unprivileged
> > users shouldn't be allowed to do it at all, or else it's safe and we
> > should drop the requirement completely. I can't say which is right,
> > unfortunately.
>
> It may not have been safe 16 years agoo, but giving invalid arguments
> to FIBMAP is safe for ext4 and ext2. This is the sort of thing that
> tools like trinity should and does test for, so I think it should be
> fine to remove the root check for FIBMAP.

Seth, can I tempt you into sending a standalone patch to remove that? :)

-serge