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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 C45EAC433DF for ; Wed, 20 May 2020 16:09:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AB98D2075F for ; Wed, 20 May 2020 16:09:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726839AbgETQJS (ORCPT ); Wed, 20 May 2020 12:09:18 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:60054 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726439AbgETQJR (ORCPT ); Wed, 20 May 2020 12:09:17 -0400 Received: from in01.mta.xmission.com ([166.70.13.51]) by out02.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jbRHM-0002da-JB; Wed, 20 May 2020 10:09:12 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in01.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1jbRHL-00070A-LM; Wed, 20 May 2020 10:09:12 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Rob Landley Cc: linux-kernel@vger.kernel.org, Linus Torvalds , Oleg Nesterov , Jann Horn , Kees Cook , Greg Ungerer , Bernd Edlinger , linux-fsdevel@vger.kernel.org, Al Viro , Alexey Dobriyan , Andrew Morton , Casey Schaufler , linux-security-module@vger.kernel.org, James Morris , "Serge E. Hallyn" , Andy Lutomirski References: <87h7wujhmz.fsf@x220.int.ebiederm.org> <87sgga6ze4.fsf@x220.int.ebiederm.org> <87v9l4zyla.fsf_-_@x220.int.ebiederm.org> <877dx822er.fsf_-_@x220.int.ebiederm.org> <87y2poyd91.fsf_-_@x220.int.ebiederm.org> Date: Wed, 20 May 2020 11:05:29 -0500 In-Reply-To: (Rob Landley's message of "Tue, 19 May 2020 16:59:06 -0500") Message-ID: <874ksaioc6.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1jbRHL-00070A-LM;;;mid=<874ksaioc6.fsf@x220.int.ebiederm.org>;;;hst=in01.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX19NAyurH9iGPP/ahHUMxq6hKHYaPv0QJ5Y= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH v2 7/8] exec: Generic execfd support X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Rob Landley writes: > On 5/18/20 7:33 PM, Eric W. Biederman wrote: >> >> Most of the support for passing the file descriptor of an executable >> to an interpreter already lives in the generic code and in binfmt_elf. >> Rework the fields in binfmt_elf that deal with executable file >> descriptor passing to make executable file descriptor passing a first >> class concept. > > I was reading this to try to figure out how to do execve(NULL, argv[], envp) to > re-exec self after a vfork() in a chroot with no /proc, and hit the most trivial > quibble ever: We have /proc/self/exe today. If I understand you correctly you would like to do the equivalent of 'execve("/proc/self/exe", argv[], envp[])' without having proc mounted. The file descriptor is stored in mm->exe_file. Probably the most straight forward implementation is to allow execveat(AT_EXE_FILE, ...). You can look at binfmt_misc for how to reopen an open file descriptor. >> --- a/fs/exec.c >> +++ b/fs/exec.c >> @@ -1323,7 +1323,10 @@ int begin_new_exec(struct linux_binprm * bprm) >> */ >> set_mm_exe_file(bprm->mm, bprm->file); >> >> + /* If the binary is not readable than enforce mm->dumpable=0 */ > > then It took me a minute yes good catch. Eric