On Wed, Aug 22, 2018 at 06:19:16PM +0200, Marc-André Lureau wrote: > Hi > > On Wed, Aug 22, 2018 at 6:07 PM, Eric Blake <ebl...@redhat.com> wrote: > > On 08/22/2018 10:58 AM, Marc-André Lureau wrote: > > > >>> At this point you might as well not bother using seccomp at all. The > >>> thread that is confined merely needs to scribble something into the > >>> stack of the unconfined thread and now it can do whatever it wants. > >> > >> > >> Actually, that message is incorrect, it should rather be "not all > >> threads will be filtered" (as described in commit message). > >> > >>> IMHO we need to find a way to get the policy to apply to those other > >>> threads. > >> > >> > >> That's what the patch is about ;) > > > > > > In other words, this patch is patching the gaping security hole that already > > exists, but... > > > >>>> +++ b/qemu-options.hx > >>>> @@ -3864,6 +3864,8 @@ Disable set*uid|gid system calls > >>>> Disable *fork and execve > >>>> @item resourcecontrol=@var{string} > >>>> Disable process affinity and schedular priority > >>>> +@item tsync=@var{bool} > >>>> +Apply seccomp filter to all threads (default is auto, and will warn if > >>>> fail) > >>> > >>> > >>> IMHO this should never exist, as setting "tsync" to anything other > >>> than "yes", is akin to just running without any sandbox. > >> > >> > >> Then we should just fail -sandbox on those systems. > > > > > > ...leaving the backdoor open. Yes, we should instead fix things to hard > > fail when -sandbox cannot fully protect the process, rather than adding a > > tsync=off backdoor to permit execution in spite of the insecurity. > > Ok, -sandbox will now require libseccomp 2.2.0 (not available in > Debian oldstable - so it will fail at configure time) and kernel >= > 3.17 (error during start). If that sounds ok, I'll update the series.
Hmm, that will cause seccomp to be unusable for RHEL-7, prior to the 7.5 kernel, which has complications wrt libvirt using -sandbox by default. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|