Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755848AbaDPSlJ (ORCPT ); Wed, 16 Apr 2014 14:41:09 -0400 Received: from mail-la0-f54.google.com ([209.85.215.54]:36796 "EHLO mail-la0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755548AbaDPSlG (ORCPT ); Wed, 16 Apr 2014 14:41:06 -0400 MIME-Version: 1.0 In-Reply-To: <20140416183614.GH31074@redhat.com> References: <20140416002010.GA5035@redhat.com> <20140416.085743.1614257692560892039.davem@davemloft.net> <1397664837.19767.410.camel@willson.li.ssimo.org> <1397667766.19767.440.camel@willson.li.ssimo.org> <20140416183614.GH31074@redhat.com> From: Andy Lutomirski Date: Wed, 16 Apr 2014 11:40:44 -0700 Message-ID: Subject: Re: [PATCH 2/2] net: Implement SO_PASSCGROUP to enable passing cgroup path To: Vivek Goyal Cc: Simo Sorce , David Miller , Tejun Heo , Daniel Walsh , "linux-kernel@vger.kernel.org" , lpoetter@redhat.com, cgroups@vger.kernel.org, kay@redhat.com, Network Development Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 16, 2014 at 11:36 AM, Vivek Goyal wrote: > On Wed, Apr 16, 2014 at 10:29:08AM -0700, Andy Lutomirski wrote: > > [..] >> >> Admittedly cgroups aren't currently as important as uid, but if this >> >> changes, then SO_PASSCGROUP, as currently written, will have *exactly* >> >> the same problem. >> > >> > Which is easy to foil by using SO_PEERCGROUP and find out who originally >> > opened the socket, which is why that is also available! >> >> Then please remove SO_PASSCGROUP. > > SO_PASSCGROUP is important because SO_PEERCGROUP does not work with unix > datagram sockets. Right. I forgot about that. > > Again going back to logging example, if some clients are logging to unix > datagram sockets, SO_PASSCGROUP is the only option to figure out cgroup > of client. Hmm. I think that, in your patch, the cgroup that is sent is the cgroup of the caller of write/send/sendmsg. What if you changed it to use the same cgroup that SO_PEERCRED would use? Would that still work? >> >> I still haven't seen any explanation for what's wrong with requiring >> senders to ask the kernel to transmit their cgroup. > > If nothing else, additional complexity and ovhead. Extra pair of messages > need to be exchanged to request and then provide the information. > > How would it work in logging example? Every time logger receives a > message, is it supposed to send another message to client to send > SCM_CGROUP? That does not sound right. No -- just have the logger send the cgroup with every message. Yes, it seems silly, but it's probably barely more expensive than with the code in your patch. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/