From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD643C43334 for ; Thu, 6 Sep 2018 15:45:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 69D712075B for ; Thu, 6 Sep 2018 15:45:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="aa57Wlz1" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 69D712075B Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730284AbeIFUV6 (ORCPT ); Thu, 6 Sep 2018 16:21:58 -0400 Received: from mail-oi0-f66.google.com ([209.85.218.66]:33854 "EHLO mail-oi0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728047AbeIFUV6 (ORCPT ); Thu, 6 Sep 2018 16:21:58 -0400 Received: by mail-oi0-f66.google.com with SMTP id 13-v6so21494064ois.1 for ; Thu, 06 Sep 2018 08:45:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=SCF/qGOGTlsPnERb2AnClt8bZvvrNKHSZvr5ZA3FL0k=; b=aa57Wlz1qcEqmNezU9oMI1c4IduE1+jZlS4oLQi3GhO8k0luazSwPnf/itreCnQuWC YvBc6yxiLs7EXup3uizv3vOekIITSlftGLa17iQXpH/qiqG8PCSvh50H5psGWi99LR+8 HdVivpK1pcFozuqMzOTsyJLdAwbSw2wl+Fwl9rgjvMvwi6qnDrzIFU/4D9dn2mrb2A/p d8ub7R/71qIZX92wWBLNURWs6h6la6dS2Z9YA+K1nEDJZeGtzLkRlMsi6mjS/u45g+MV rQo1QkOvTZXB2kqehGeOC85po2j8QsLDmBhXUy3mU/EfaRm5j1IJzNw+EYvwjymRwWuf ELxQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=SCF/qGOGTlsPnERb2AnClt8bZvvrNKHSZvr5ZA3FL0k=; b=RsnKFwaqAVN0XeEWjg9czWIMyxrb4PnCssH5kRlH0BMArKA8d4yx6GK4pY5Z9taKcL rtq61q8HrVExBAzripsdkPVxj8oQIvN+AP8eNX1exxWyO02L5voUUHet0rBeYaf6tX4Z Yn2X0M4Wq+A16SqQ7SjfW6lgH7YD1AYdpz36ffGwpBOz1Zu8KKQZRZ1/uiWozjpHUMom 1kdmkvKixpCDgT/CdBBYGrfLF2s/cE2YcDouEQcAkpcfT8nJNqvmN8knGgqmZ0PYUgsA T6DRS5xBt+BFaqL4yb+jG6BQyhsrM9jBoGRxPoVfoQ8G4eDLl7X6L7bnxVvs+3RbbMOu Ws2w== X-Gm-Message-State: APzg51C+EbS7qmB4WHx2v1Qi7TyIbXAwaGep5IdzSMc3fDChi9pZDt4z dptIgEuDIv2dWdothJwF9vIXOWnGFG7ohbdwSA9BYA== X-Google-Smtp-Source: ANB0VdZnZ5IzqRwr29PPnWagZEt+JFJXf5cTrL0IpHw6BbSWedX58v1ysRQWamQ8EcxSHrEvcuBHlE9kvBwZjJjZuIw= X-Received: by 2002:aca:4784:: with SMTP id u126-v6mr3501091oia.229.1536248751783; Thu, 06 Sep 2018 08:45:51 -0700 (PDT) MIME-Version: 1.0 References: <20180906152859.7810-1-tycho@tycho.ws> <20180906152859.7810-4-tycho@tycho.ws> In-Reply-To: <20180906152859.7810-4-tycho@tycho.ws> From: Jann Horn Date: Thu, 6 Sep 2018 17:45:25 +0200 Message-ID: Subject: Re: [PATCH v6 3/5] seccomp: add a way to get a listener fd from ptrace To: Tycho Andersen Cc: Kees Cook , kernel list , containers@lists.linux-foundation.org, Linux API , Andy Lutomirski , Oleg Nesterov , "Eric W. Biederman" , "Serge E. Hallyn" , Christian Brauner , Tyler Hicks , suda.akihiro@lab.ntt.co.jp Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 6, 2018 at 5:29 PM Tycho Andersen wrote: > > As an alternative to SECCOMP_FILTER_FLAG_GET_LISTENER, perhaps a ptrace() > version which can acquire filters is useful. There are at least two reasons > this is preferable, even though it uses ptrace: > > 1. You can control tasks that aren't cooperating with you > 2. You can control tasks whose filters block sendmsg() and socket(); if the > task installs a filter which blocks these calls, there's no way with > SECCOMP_FILTER_FLAG_GET_LISTENER to get the fd out to the privileged task. [...] > +long seccomp_new_listener(struct task_struct *task, > + unsigned long filter_off) > +{ > + struct seccomp_filter *filter; > + struct file *listener; > + int fd; > + > + if (!capable(CAP_SYS_ADMIN)) > + return -EACCES; > + > + filter = get_nth_filter(task, filter_off); > + if (IS_ERR(filter)) > + return PTR_ERR(filter); > + > + fd = get_unused_fd_flags(0); > + if (fd < 0) { > + __put_seccomp_filter(filter); > + return fd; > + } > + > + listener = init_listener(task, task->seccomp.filter); Did you mean to write something like `init_listener(task, filter)` here?