[PATCH 0/6] File Sealing & memfd_create()

[Andy Lutomirski]

On Thu, Apr 10, 2014 at 3:57 PM, David Herrmann <dh.herrmann at gmail.com> wrote:
> Hi
>
> On Thu, Apr 10, 2014 at 11:16 PM, Andy Lutomirski <luto at amacapital.net> wrote:
>> Would it make sense for the initial mode on a memfd inode to be 000?
>> Anyone who finds this to be problematic could use fchmod to fix it.
>
> memfd_create() should be subject to umask() just like anything else.
> That should solve any possible race here, right?

Yes, but how many people will actually think about umask when doing
things that don't really look like creating files?

/proc/pid/fd is a really weird corner case in which the mode of an
inode that doesn't have a name matters.  I suspect that almost no one
will ever want to open one of these things out of /proc/self/fd, and
those who do should be made to think about it.

It also avoids odd screwups where things are secure until someone runs
them with umask 000.

--Andy