lkml.org 
[lkml]   [2014]   [Jul]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: General flags to turn things off (getrandom, pid lookup, etc)
On Jul 27, 2014 5:06 PM, "Theodore Ts'o" <tytso@mit.edu> wrote:
>
> On Fri, Jul 25, 2014 at 11:30:48AM -0700, Andy Lutomirski wrote:
> >
> > There is recent interest in having a way to turn generally-available
> > kernel features off. Maybe we should add a good one so we can stop
> > bikeshedding and avoid proliferating dumb interfaces.
>
> I believe the seccomp infrastructure (which is already upstream)
> should be able to do most of what you want, at least with respect to
> features which are exposed via system calls (which was most of your
> list).

Seccomp can't really restrict lookups of non-self pids. In fact, this
feature idea started out as a response to a patch adding a kind of
nasty seccomp feature to make it sort of possible.

I agree that that seccomp can turn off GRND_RANDOM, but how is it
supposed to do it in such a way that the filtered software will fall
back to something sensible? -ENOSYS? -EPERM? Something else?

I think that -ENOSYS is clearly wrong, but standardizing this would be
nice. Admittedly, adding something fancy like this for GRND_RANDOM
may not be appropriate.

--Andy

>
> It won't cover x86 specific things like restricting RDTSC or CPUID
> (and as far as I know you can't intercept the CPUID instruction), but
> I'm not sure it matters. I don't really see the point, myself.
>
> - Ted


\
 
 \ /
  Last update: 2014-07-28 01:01    [W:0.158 / U:0.160 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site