From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f181.google.com ([209.85.213.181]:33629 "EHLO mail-ig0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754252AbbLDUou (ORCPT ); Fri, 4 Dec 2015 15:44:50 -0500 Received: by igcmv3 with SMTP id mv3so44120843igc.0 for ; Fri, 04 Dec 2015 12:44:50 -0800 (PST) Date: Fri, 4 Dec 2015 14:43:19 -0600 From: Seth Forshee To: "Serge E. Hallyn" Cc: "Eric W. Biederman" , Miklos Szeredi , Alexander Viro , Serge Hallyn , Richard Weinberger , Austin S Hemmelgarn , linux-bcache@vger.kernel.org, dm-devel@redhat.com, linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org, fuse-devel@lists.sourceforge.net, linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov Subject: Re: [PATCH 18/19] fuse: Restrict allow_other to the superblock's namespace or a descendant Message-ID: <20151204204319.GF147214@ubuntu-hedt> References: <1449070821-73820-1-git-send-email-seth.forshee@canonical.com> <1449070821-73820-19-git-send-email-seth.forshee@canonical.com> <20151204200541.GI3624@mail.hallyn.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151204200541.GI3624@mail.hallyn.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Fri, Dec 04, 2015 at 02:05:41PM -0600, Serge E. Hallyn wrote: > Quoting Seth Forshee (seth.forshee@canonical.com): > > Unprivileged users are normally restricted from mounting with the > > allow_other option by system policy, but this could be bypassed > > for a mount done with user namespace root permissions. In such > > cases allow_other should not allow users outside the userns > > to access the mount as doing so would give the unprivileged user > > the ability to manipulate processes it would otherwise be unable > > to manipulate. Restrict allow_other to apply to users in the same > > userns used at mount or a descendant of that namespace. > > > > Signed-off-by: Seth Forshee > > --- > > fs/fuse/dir.c | 10 ++++++++-- > > 1 file changed, 8 insertions(+), 2 deletions(-) > > > > diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c > > index f67f4dd86b36..5b8edb1203b8 100644 > > --- a/fs/fuse/dir.c > > +++ b/fs/fuse/dir.c > > @@ -1018,8 +1018,14 @@ int fuse_allow_current_process(struct fuse_conn *fc) > > { > > const struct cred *cred; > > > > - if (fc->flags & FUSE_ALLOW_OTHER) > > - return 1; > > + if (fc->flags & FUSE_ALLOW_OTHER) { > > + struct user_namespace *ns; > > + for (ns = current_user_ns(); ns; ns = ns->parent) { > > + if (ns == fc->user_ns) > > + return 1; > > + } > > use current_in_userns() ? Yes, it should. I wrote this before I wrote the patch which adds that function and never thought to go back to change it here.