Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752487AbbGPNYh (ORCPT ); Thu, 16 Jul 2015 09:24:37 -0400 Received: from emvm-gh1-uea08.nsa.gov ([63.239.67.9]:62725 "EHLO emvm-gh1-uea08.nsa.gov" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751122AbbGPNYf (ORCPT ); Thu, 16 Jul 2015 09:24:35 -0400 X-TM-IMSS-Message-ID: <1802e2220003328b@nsa.gov> Message-ID: <55A7B055.4050809@tycho.nsa.gov> Date: Thu, 16 Jul 2015 09:23:33 -0400 From: Stephen Smalley Organization: National Security Agency User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Seth Forshee , "Eric W. Biederman" , Alexander Viro , Paul Moore , Eric Paris CC: Serge Hallyn , James Morris , linux-kernel@vger.kernel.org, Andy Lutomirski , linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 6/7] selinux: Ignore security labels on user namespace mounts References: <1436989569-69582-1-git-send-email-seth.forshee@canonical.com> <1436989569-69582-7-git-send-email-seth.forshee@canonical.com> In-Reply-To: <1436989569-69582-7-git-send-email-seth.forshee@canonical.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2075 Lines: 58 On 07/15/2015 03:46 PM, Seth Forshee wrote: > Unprivileged users should not be able to supply security labels > in filesystems, nor should they be able to supply security > contexts in unprivileged mounts. For any mount where s_user_ns is > not init_user_ns, force the use of SECURITY_FS_USE_NONE behavior > and return EPERM if any contexts are supplied in the mount > options. > > Signed-off-by: Seth Forshee I think this is obsoleted by the subsequent discussion, but just for the record: this patch would cause the files in the userns mount to be left with the "unlabeled" label, and therefore under typical policies, completely inaccessible to any process in a confined domain. > --- > security/selinux/hooks.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > index 459e71ddbc9d..eeb71e45ab82 100644 > --- a/security/selinux/hooks.c > +++ b/security/selinux/hooks.c > @@ -732,6 +732,19 @@ static int selinux_set_mnt_opts(struct super_block *sb, > !strcmp(sb->s_type->name, "pstore")) > sbsec->flags |= SE_SBGENFS; > > + /* > + * If this is a user namespace mount, no contexts are allowed > + * on the command line and security labels mus be ignored. > + */ > + if (sb->s_user_ns != &init_user_ns) { > + if (context_sid || fscontext_sid || rootcontext_sid || > + defcontext_sid) > + return -EPERM; > + sbsec->behavior = SECURITY_FS_USE_NONE; > + goto out_set_opts; > + } > + > + > if (!sbsec->behavior) { > /* > * Determine the labeling behavior to use for this > @@ -813,6 +826,7 @@ static int selinux_set_mnt_opts(struct super_block *sb, > sbsec->def_sid = defcontext_sid; > } > > +out_set_opts: > rc = sb_finish_set_opts(sb); > out: > mutex_unlock(&sbsec->lock); > -- 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/