On Mon, Oct 08, 2018 at 04:58:05PM +0200, Christian Brauner wrote: > On Thu, Sep 27, 2018 at 04:48:39PM -0600, Tycho Andersen wrote: > > On Thu, Sep 27, 2018 at 02:31:24PM -0700, Kees Cook wrote: > > > I have to say, I'm vaguely nervous about changing the semantics here > > > for passing back the fd as the return code from the seccomp() syscall. > > > Alternatives seem less appealing, though: changing the meaning of the > > > uargs parameter when SECCOMP_FILTER_FLAG_NEW_LISTENER is set, for > > > example. Hmm. > > > > From my perspective we can drop this whole thing. The only thing I'll > > ever use is the ptrace version. Someone at some point (I don't > > remember who, maybe stgraber) suggested this version would be useful > > as well. > > So I think we want to have the ability to get an fd via seccomp(). > Especially, if we all we worry about are weird semantics. When we > discussed this we knew the whole patchset was going to be weird. :) > > This is a seccomp feature so seccomp should - if feasible - equip you > with everything to use it in a meaningful way without having to go > through a different kernel api. I know ptrace and seccomp are > already connected but I still find this cleaner. :) > > Another thing is that the container itself might be traced for some > reason while you still might want to get an fd out. Sure, I don't see the problem here. > Also, I wonder what happens if you want to filter the ptrace() syscall > itself? Then you'd deadlock? No, are you confusing the tracee with the tracer here? Filtering ptrace() will happen just like any other syscall... what would you deadlock with? > Also, it seems that getting an fd via ptrace requires CAP_SYS_ADMIN in > the inital user namespace (which I just realized now) whereas getting > the fd via seccomp() doesn't seem to. Yep, I'll leave this discussion to the other thread. Tycho
