From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751701AbaKUSir (ORCPT ); Fri, 21 Nov 2014 13:38:47 -0500 Received: from mail-lb0-f171.google.com ([209.85.217.171]:48251 "EHLO mail-lb0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751218AbaKUSip (ORCPT ); Fri, 21 Nov 2014 13:38:45 -0500 MIME-Version: 1.0 In-Reply-To: <87ppcgju9w.fsf@x220.int.ebiederm.org> References: <1414013060-137148-1-git-send-email-seth.forshee@canonical.com> <1414013060-137148-3-git-send-email-seth.forshee@canonical.com> <20141111140454.GD333@tucsk> <87mw7xd9zt.fsf@x220.int.ebiederm.org> <20141112130915.GG333@tucsk> <20141112162254.GB31775@ubuntu-hedt> <20141118152156.GA21726@ubuntu-mba51> <20141119140911.GA27009@mail.hallyn.com> <20141121164441.GA1730@ubuntu-mba51> <87ppcgju9w.fsf@x220.int.ebiederm.org> From: Andy Lutomirski Date: Fri, 21 Nov 2014 10:38:23 -0800 Message-ID: Subject: Re: [PATCH v5 2/4] fuse: Support fuse filesystems outside of init_user_ns To: "Eric W. Biederman" Cc: Seth Forshee , Miklos Szeredi , "Serge E. Hallyn" , "Serge H. Hallyn" , Michael j Theall , fuse-devel , Kernel Mailing List , Linux-Fsdevel 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 Fri, Nov 21, 2014 at 10:14 AM, Eric W. Biederman wrote: > - Tweak the file capability code to look at s_user_ns and treat it > properly. > > - Tweak the security checks to allow setting file capabilities and > other security xattrs if we have the appropriate capabilities in > s_user_ns. > Thinking about this some more, what do you mean by tweaking the file capability code to look at s_user_ns and treat it properly? I think that the semantics should be that cap_inode_setxattr should check ns_capable wrt s_user_ns, but that the fscap *consumer* should check the mount as in my may_suid patch (and maybe also check s_user_ns). There is legacy code that starts a FUSE server as global root, mounts the thing in a mount namespace belonging to an unprivileged user ns, and (I think) hands the /dev/fuse fd to that unprivileged code. Without the mount ns check, that FUSE server can take over the system. With the mount ns check, it's safe. --Andy > > When those bits are done we can tweak the fuse patches to also set > s_user_ns. > > As for MNT_NO_SUID if fuse wants to enforce that in some way. I don't > particularly care, but I don't think that makes sense as a vfs property. > > Eric -- Andy Lutomirski AMA Capital Management, LLC