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=-2.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 BCF4FC2D0DB for ; Tue, 28 Jan 2020 18:04:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9594D2173E for ; Tue, 28 Jan 2020 18:04:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="j0snadR+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726066AbgA1SEo (ORCPT ); Tue, 28 Jan 2020 13:04:44 -0500 Received: from mail-il1-f193.google.com ([209.85.166.193]:34622 "EHLO mail-il1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726318AbgA1SEo (ORCPT ); Tue, 28 Jan 2020 13:04:44 -0500 Received: by mail-il1-f193.google.com with SMTP id l4so11504551ilj.1 for ; Tue, 28 Jan 2020 10:04:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:from:to:cc:references:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=QkOPikTFWGd6EkDEB6d3CyXk7VJdtAlQAyhbj1b204Q=; b=j0snadR+nkaKoJfQhsezQp18UioFNFqQVsSyabvZV8ZJsyFd9vsHZC2ndYR+8na2BF uMxravMg1HvOCWq+ic2F3nCum664c8LEo5mOSLWH6Siq6MV1bNPFpIIGyog7GHSRRm9x 8eARGGfltWId/7vOlLjbGZLAg6xVkN+uRDaTJ8eXEsKOJjoAtMUs7NR5jlFJVjXZCGFz ioK3YOVjGDg5oecj2+c6ch7AElIz4KzL7eXICu1Xh5L/F8x0N437Q3ZUjIiNjXrnNRyW a8o95C8ch22Y4kwEL8fc7iCRna39BpVXOykrHoJ7aogWXGp7zR/3kQ1e6TyDIl/WKpwC Caog== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:from:to:cc:references:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=QkOPikTFWGd6EkDEB6d3CyXk7VJdtAlQAyhbj1b204Q=; b=YGVb0NfYbmhPTVCBbg5LVAaHUkJW4R2gMCiyAg1UTZzzjWs0hA66raLtcFO4DJHrGx RJvqqvAf1kl2d2Tutsl3PGjEIxz1iYcxRKH5l7D7hPE0a6OLcPUz/mc8yrR0WO7+0TtR BQdcRLKRHCITCN0CDvt33aR1tH3Nkfeuyul+XVAChVVTqVsEDBPIFbiUYK3/5QZNwXS+ crVCDrQ4ybEGIlX+4jY7Y10aGzBASPpqapQWEW0yA0aIMZlQumlUH4VPg/sAg+QxmYkC 07rLTHZJUSOX0+l2I1cSdr2X91ShwLJe5iXpKl2f5lxl/Jm4GBuYm87QdMwtzAXP/3ed 9MzA== X-Gm-Message-State: APjAAAWHd0LBuago5UYjPTVpuxp3bEN2ImHdlVJcJqHNQYo9SM31kmyW +hvPh+wsvaOzFizDPqtLw4RBfw== X-Google-Smtp-Source: APXvYqwjjoCWsyM81+VMManfxYXzhJz0ZT/2FhMUAyABNm4cJLUjAKeiswdJsdyAjbGP2lksjrtKmg== X-Received: by 2002:a92:7509:: with SMTP id q9mr19964501ilc.67.1580234683021; Tue, 28 Jan 2020 10:04:43 -0800 (PST) Received: from [192.168.1.159] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id n12sm4611657ion.25.2020.01.28.10.04.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 28 Jan 2020 10:04:42 -0800 (PST) Subject: Re: IORING_REGISTER_CREDS[_UPDATE]() and credfd_create()? From: Jens Axboe To: Stefan Metzmacher Cc: io-uring , Linux API Mailing List , Pavel Begunkov References: <688e187a-75dd-89d9-921c-67de228605ce@samba.org> <1ac31828-e915-6180-cdb4-36685442ea75@kernel.dk> Message-ID: <0d4f43d8-a0c4-920b-5b8f-127c1c5a3fad@kernel.dk> Date: Tue, 28 Jan 2020 11:04:40 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <1ac31828-e915-6180-cdb4-36685442ea75@kernel.dk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 1/28/20 10:19 AM, Jens Axboe wrote: > On 1/28/20 9:19 AM, Jens Axboe wrote: >> On 1/28/20 9:17 AM, Stefan Metzmacher wrote: >>> Am 28.01.20 um 17:10 schrieb Jens Axboe: >>>> On 1/28/20 3:18 AM, Stefan Metzmacher wrote: >>>>> Hi Jens, >>>>> >>>>> now that we have IORING_FEAT_CUR_PERSONALITY... >>>>> >>>>> How can we optimize the fileserver case now, in order to avoid the >>>>> overhead of always calling 5 syscalls before io_uring_enter()?: >>>>> >>>>> /* gain root again */ >>>>> setresuid(-1,0,-1); setresgid(-1,0,-1) >>>>> /* impersonate the user with groups */ >>>>> setgroups(num, grps); setresgid(-1,gid,-1); setresuid(-1,uid,-1); >>>>> /* trigger the operation */ >>>>> io_uring_enter(); >>>>> >>>>> I guess some kind of IORING_REGISTER_CREDS[_UPDATE] would be >>>>> good, together with a IOSQE_FIXED_CREDS in order to specify >>>>> credentials per operation. >>>>> >>>>> Or we make it much more generic and introduce a credsfd_create() >>>>> syscall in order to get an fd for a credential handle, maybe >>>>> together with another syscall to activate the credentials of >>>>> the current thread (or let a write to the fd trigger the activation >>>>> in order to avoid an additional syscall number). >>>>> >>>>> Having just an fd would allow IORING_REGISTER_CREDS[_UPDATE] >>>>> to be just an array of int values instead of a more complex >>>>> structure to define the credentials. >>>> >>>> I'd rather avoid having to add more infrastructure for this, even if >>>> credsfd_create() would be nifty. >>>> >>>> With that in mind, something like: >>>> >>>> - Application does IORING_REGISTER_CREDS, which returns some index >>>> >>>> - Add a IORING_OP_USE_CREDS opcode, which sets the creds associated >>>> with dependent commands >>>> - Actual request is linked to the IORING_OP_USE_CREDS command, any >>>> link off IORING_OP_USE_CREDS will use those credentials >>> >>> Using links for this sounds ok. >> >> Great! I'll try and hack this up and see how it turns out. >> >>>> - IORING_UNREGISTER_CREDS removes the registered creds >>>> >>>> Just throwing that out there, definitely willing to entertain other >>>> methods that make sense for this. Trying to avoid needing to put this >>>> information in the SQE itself, hence the idea to use a chain of links >>>> for it. >>>> >>>> The downside is that we'll need to maintain an array of key -> creds, >>>> but that's probably not a big deal. >>>> >>>> What do you think? >>> >>> So IORING_REGISTER_CREDS would be a simple operation that just takes a >>> snapshot of the current_cred() and returns an id that can be passed to >>> IORING_OP_USE_CREDS or IORING_UNREGISTER_CREDS? >> >> Right, you would not pass in any arguments, it'd have to be run from the >> personality you wish to register. It simply returns an integer, which is >> a key to use for IORING_OP_USE_CREDS, or at the end for >> IORING_UNREGISTER_CREDS when you no longer wish to use this personality. >> >>>> Ideally I'd like to get this done for 5.6 even if we >>>> are a bit late, so you'll have everything you need with that release. >>> >>> That would be great! >> >> Crossing fingers... > > OK, so here are two patches for testing: > > https://git.kernel.dk/cgit/linux-block/log/?h=for-5.6/io_uring-vfs-creds > > #1 adds support for registering the personality of the invoking task, > and #2 adds support for IORING_OP_USE_CREDS. Right now it's limited to > just having one link, it doesn't support a chain of them. > > I'll try and write a test case for this just to see if it actually works, > so far it's totally untested. > > Adding Pavel to the CC. Minor tweak to ensuring we do the right thing for async offload as well, and it tests fine for me. Test case is: - Run as root - Register personality for root - create root only file - check we can IORING_OP_OPENAT the file - switch to user id test - check we cannot IORING_OP_OPENAT the file - check that we can open the file with IORING_OP_USE_CREDS linked -- Jens Axboe