From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id A7A54B92 for ; Tue, 24 Jan 2017 21:01:20 +0000 (UTC) Received: from mail-vk0-f54.google.com (mail-vk0-f54.google.com [209.85.213.54]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id D8B58214 for ; Tue, 24 Jan 2017 21:01:19 +0000 (UTC) Received: by mail-vk0-f54.google.com with SMTP id x75so120959839vke.2 for ; Tue, 24 Jan 2017 13:01:19 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <87tw8oojv2.fsf@xmission.com> References: <87tw8oojv2.fsf@xmission.com> From: Andy Lutomirski Date: Tue, 24 Jan 2017 13:00:58 -0800 Message-ID: To: "Eric W. Biederman" Content-Type: text/plain; charset=UTF-8 Cc: Josh Armour , Greg KH , Djalal Harouni , "ksummit-discuss@lists.linuxfoundation.org" Subject: Re: [Ksummit-discuss] security-related TODO items? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, Jan 24, 2017 at 2:03 AM, Eric W. Biederman wrote: > Andy Lutomirski writes: > >> On Fri, Jan 20, 2017 at 2:38 PM, Kees Cook wrote: >>> Hi, >>> >>> I've already got various Kernel Self-Protection Project TODO items >>> collected[1] (of varying size and complexity), but recently Google's >>> Patch Reward Program[2] is trying to expand by helping create a bounty >>> program for security-related TODOs. KSPP is just one corner of >>> interest in the kernel, and I'd love to know if any other maintainers >>> have TODO items that they'd like to see get done (and Google would >>> potentially provide bounty money for). >>> >>> Let me know your security wish-lists, and I'll collect them all into a >>> single place. And if there is a better place than ksummit-discuss to >>> reach maintainers, I'm all ears. LKML tends to mostly just serve as a >>> public archive. :) >>> >> >> Here's another one: split up and modernize /proc. >> >> I'm imagining a whole series of changes: >> >> - Make a sysctlfs. You could mount it and get all the sysctls if you >> have global privilege. If you only have privilege relative to some >> namespace, you could pass a mount option like -o scope=net to get just >> sysctls that belong to the mounting process' netns. If done >> carefully, this should be safe for unprivileged mounting without the >> fs_fully_visible() checks. > > Nope. Because the fs_fully_visible checks are there to support a root > policy of what can be used. Any filesystem with content needs > fs_fully_visible or another way for root to say no you can't access > these files. > > cgroupfs gets a pass from me because we can set the number of cgroup > namespaces to 0, and because changing it will break userspace. > > Besides bind if you split up proc into pieces bind mounts should be > sufficient and you should not need to allow unprivileged users to mount > any of the pieces of proc. > Let me clarify what I meant. Currently, IIUC there are a large number of sysctls that are global to the system and a smaller number that only affect a single namespace. If you have global privilege, you could do: # mount -t sysctlfs -o scope=global none /whatever This would be disallowed entirely if you don't have global privilege. You could also do: # mount -t sysctlfs -o scope=net none /whatever This would *not* require global privilege or fs_fully_visible, but it would require ns_capable(current->nsproxy->net_ns, CAP_NET_ADMIN). You would get a limited syctlfs that only shows sysctls that are local to the network namespace of the mounter. Does that make sense? --Andy