From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: disablenetwork (v5): Simplify the disablenetwork sendmsg hook. Date: Sun, 17 Jan 2010 20:04:06 +0200 Message-ID: <20100117180405.GA32339@redhat.com> References: <20100117161053.GG3420@redhat.com> <20100117170431.GA2949@heat> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Anthony Liguori , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-security-module@vger.kernel.org To: Michael Stone Return-path: Content-Disposition: inline In-Reply-To: <20100117170431.GA2949@heat> Sender: linux-security-module-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Sun, Jan 17, 2010 at 12:04:32PM -0500, Michael Stone wrote: > Michael Tsirkin wrote: >> On Fri, Jan 15, 2010 at 03:12:46AM -0500, Michael Stone wrote: >>> The idea is that calls like >>> >>> sendto(fd, buffer, len, 0, NULL, 0); >>> send(fd, buffer, len, 0) >>> write(fd, buffer, len) >>> >>> are all to be permitted but that calls like >>> >>> sendto(fd, buffer, len, 0, (struct sockadr *) &addr, sizeof(addr)); >>> >>> are to be rejected when the current task's network is disabled on the grounds >>> that the former calls must use previously connected sockets but that the latter >>> socket need not have been previously connected. >>> >>> Signed-off-by: Michael Stone >> >> Michael, if I understand correctly, with this patch one could use >> disablenetwork to pass an af_packet socket bound to a device to a >> task, and make sure that the task does not use it to inject packets into >> another device? > > Michael, > > Thanks for writing. If I understand you correctly, you're asking: > > May a network-disabled process use recvmsg() with SCM_RIGHTS control messages > to receive a file descriptor pointing to previously connected or bound > AF_PACKET socket and, having received such an fd, may the network-disabled > process use the socket normally? > > If I've understood correctly, then the answer is "yes, to the extent that you > can't do stupid things with sendmsg(), fnctl(), ioctl(), and friends." > > I intend to look more carefully at the ability to use those calls to do stupid > things in coming weeks. > > Does this help? > > Regards, > > Michael > > P.S. - Incidentally, what is the nature of your interest? We discussed using af_packet sockets for networking in qemu. qemu is a large project so it might not be a great idea to run it as root all the time: a better idea is to e.g. get fd from a priveledged server. However, we'd like to limit qemu even more, so that it can only use the fd for send/receive. > (And was your question intentionally or accidentally off-list?) Oops. Adding it back. -- MST