Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933403AbaJVVtN (ORCPT ); Wed, 22 Oct 2014 17:49:13 -0400 Received: from mail-lb0-f181.google.com ([209.85.217.181]:56440 "EHLO mail-lb0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932981AbaJVVtL (ORCPT ); Wed, 22 Oct 2014 17:49:11 -0400 MIME-Version: 1.0 In-Reply-To: <1414013060-137148-4-git-send-email-seth.forshee@canonical.com> References: <1414013060-137148-1-git-send-email-seth.forshee@canonical.com> <1414013060-137148-4-git-send-email-seth.forshee@canonical.com> From: Andy Lutomirski Date: Wed, 22 Oct 2014 14:48:48 -0700 Message-ID: Subject: Re: [PATCH v5 3/4] fuse: Restrict allow_other to the superblock's namespace or a descendant To: Seth Forshee Cc: Miklos Szeredi , "Eric W. Biederman" , "Serge H. Hallyn" , Michael j Theall , fuse-devel@lists.sourceforge.net, "linux-kernel@vger.kernel.org" , Linux FS Devel 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 Wed, Oct 22, 2014 at 2:24 PM, Seth Forshee wrote: > 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. Therefore access with allow_other should be > restricted to users in the userns as the superblock or a > descendant of that namespace. Looks good to me. Reviewed-by: Andy Lutomirski > > Cc: Eric W. Biederman > Cc: Serge H. Hallyn > Cc: Andy Lutomirski > 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 123db1e06c78..b23ec5c1ff18 100644 > --- a/fs/fuse/dir.c > +++ b/fs/fuse/dir.c > @@ -1091,8 +1091,14 @@ 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; > + } > + return 0; > + } > > cred = current_cred(); > if (uid_eq(cred->euid, fc->user_id) && > -- > 1.9.1 > -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/