From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [PATCH] net:ppp: replace too strict capability restriction on opening /dev/ppp Date: Sun, 19 Jun 2016 22:02:02 -0700 Message-ID: <87wplkihbp.fsf@tassilo.jf.intel.com> References: <44A9BDB8-754B-4402-BD09-6381229C07C5@tuna.tsinghua.edu.cn> Mime-Version: 1.0 Content-Type: text/plain Cc: netdev@vger.kernel.org, Hannes Frederic Sowa , Richard Weinberger , Guillaume Nault , Miao Wang To: Shanker Wang Return-path: Received: from mga02.intel.com ([134.134.136.20]:38220 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751701AbcFTFCG (ORCPT ); Mon, 20 Jun 2016 01:02:06 -0400 In-Reply-To: <44A9BDB8-754B-4402-BD09-6381229C07C5@tuna.tsinghua.edu.cn> (Shanker Wang's message of "Sun, 19 Jun 2016 01:38:55 +0200") Sender: netdev-owner@vger.kernel.org List-ID: Shanker Wang writes: > This patch removes the check for CAP_NET_ADMIN in the initial namespace > when opening /dev/open. Instead, CAP_NET_ADMIN is checked in the user > namespace the net namespace was created so that /dev/ppp cat get opened > in a unprivileged container. Seems dangerous. From a quick look at the PPP ioctl there is no limit how many PPP devices this can create. So a container having access to this would be able to fill all kernel memory. Probably needs more auditing and hardening first. In general there seems to be a lot of attack surface for root in PPP. -Andi -- ak@linux.intel.com -- Speaking for myself only