Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752956Ab3HOFAE (ORCPT ); Thu, 15 Aug 2013 01:00:04 -0400 Received: from mail-qa0-f45.google.com ([209.85.216.45]:36622 "EHLO mail-qa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751140Ab3HOFAA (ORCPT ); Thu, 15 Aug 2013 01:00:00 -0400 MIME-Version: 1.0 X-Originating-IP: [86.59.245.170] In-Reply-To: <87a9kkax0j.fsf@xmission.com> References: <87a9kkax0j.fsf@xmission.com> Date: Thu, 15 Aug 2013 06:59:59 +0200 Message-ID: Subject: Re: DoS with unprivileged mounts From: Miklos Szeredi To: "Eric W. Biederman" Cc: "Serge E. Hallyn" , Al Viro , Linux-Fsdevel , Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1215 Lines: 32 On Wed, Aug 14, 2013 at 9:32 PM, Eric W. Biederman wrote: >> The solution is also theoretically simple: mounts in unpriv namespaces >> are marked "volatile" and are dissolved on an unlink type operation. >> >> Such volatile mounts would be useful in general too. > > Agreed. > > This is a problem that is a general pain with mount namespaces in > general. > > I think the real technical hurdle is finding the mounts t in some random > mount namespace. Once we can do that relatively efficiently the rest > becomes simple. We already have a "struct mountpoint" hashed on the dentry. Chaining mounts on that mountpoint would be trivial. And we need a MNT_VOLATILE flag and that's it. If we fear that traversing the list of mounts on the dentry to check for non-volatile ones then we could also add a separate volatile counter to struct mountpoint and a matching flag to the dentry. But I don't think that's really necessary. Thanks, Miklos -- 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/