From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932097AbcFJJJJ (ORCPT ); Fri, 10 Jun 2016 05:09:09 -0400 Received: from mail-lf0-f43.google.com ([209.85.215.43]:33383 "EHLO mail-lf0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752173AbcFJJJB (ORCPT ); Fri, 10 Jun 2016 05:09:01 -0400 From: Mikael Pettersson X-Google-Original-From: "Mikael Pettersson" MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <22362.33704.293079.558345@gargle.gargle.HOWL> Date: Fri, 10 Jun 2016 11:08:56 +0200 To: Andy Lutomirski Cc: Kees Cook , "linux-kernel\@vger.kernel.org" Subject: Re: SIGSYS annoyance In-Reply-To: References: X-Mailer: VM 8.1.2 under 24.5.1 (x86_64-redhat-linux-gnu) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andy Lutomirski writes: > On Mon, Jun 6, 2016 at 9:03 AM, Kees Cook wrote: > > On Fri, Jun 3, 2016 at 10:16 PM, Andy Lutomirski wrote: > >> https://bugzilla.mozilla.org/show_bug.cgi?id=1176099 > >> > >> Should SIGSYS be delivered to the handler even if blocked? What, if > >> anything, does POSIX say? All I can find is in pthread_sigmask(3p): > >> > >> If any of the SIGFPE, SIGILL, SIGSEGV, or SIGBUS signals are generated > >> while they are blocked, the result is undefined, unless the signal was > >> generated by the action of another process, or by one of the functions > >> kill(), pthread_kill(), raise(), or sigqueue(). > >> > >> It would be easy enough to change our behavior so that we deliver the > >> signal even if it's blocked or to at least add a flag so that users > >> can request that behavior. > > > > I had trouble following that bug. It sounded like glib just needed a > > way to define its signal mask, and that's what they ended up > > implementing? > > > > I think the current behavior is correct. SIGSYS is being generated by > > the running process (i.e. the seccomp filter) and if it has a handler > > but the signal is blocked, we should treat it as uncaught and kill. On > > the other hand, it could be seen like "raise", in which case the > > blocking should be ignored? Is there an active problem somewhere here? > > It seems like the referenced bug has been fixed already. > > Agreed. > > It could make sense to have a new sigaction flag SA_FORCE: when set, > if a non-default handler is installed, the signal is blocked, and the > signal is triggered synchronously (forced), then the handler will be > called. But that isn't specific to seccomp. Blocking a signal is a very deliberate act. If some piece of code wants to force-deliver it, it can unblock it first. IOW, I don't see the need for this SA_FORCE thing.