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 06F6DC2D0DB for ; Thu, 30 Jan 2020 15:29:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CE36620707 for ; Thu, 30 Jan 2020 15:29:33 +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="Z55DQngx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727208AbgA3P3d (ORCPT ); Thu, 30 Jan 2020 10:29:33 -0500 Received: from mail-io1-f67.google.com ([209.85.166.67]:33477 "EHLO mail-io1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727217AbgA3P3d (ORCPT ); Thu, 30 Jan 2020 10:29:33 -0500 Received: by mail-io1-f67.google.com with SMTP id z8so4493255ioh.0 for ; Thu, 30 Jan 2020 07:29:32 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=OhK06CA3YzAzN+bOzkkl05V2NgQ7hdpBskjx0RBNIgQ=; b=Z55DQngxsnsYFCrXpbLkjaQWg9zQ2oQh+VqVKZMRkvOs4l/cTBL11kQ24AUyR/5WHU yk0lC3J2Z9vrq8qOuxnRe61SytIgq3TojUu3D0vhvRoUrdEWjkpsgVJTQcdlw5EJ/ki+ 1qONJ/mGwUH85kFbV6sWZhXtQXfhENCGg01lZgRWdy9Z1Op6QyyUlp9G/jKC8o59SxP6 yajsgVIMrQ2o+1+knBHMT06mycCPkjWu3GnemFRownkDe48nn8M7i0fN48ARxXJHtf5Y rmT4zVTvxqwtpTTx13LJ5kU7tTTPSRnOoqjdvgha8NLSZV8oTgXflYKado4+vSoqu84K B69Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=OhK06CA3YzAzN+bOzkkl05V2NgQ7hdpBskjx0RBNIgQ=; b=KnvK+kvk3dpHw3oOKm7nsmssS+r7ZAGvNdjPIT+5hlFiIIPLMo2nAXJF2qOf4+22vG HJFvzF86sPDzIyUnF4sCd56eXDet4Wkmi/ahOoy3jxm/sHyHP2kPppyGVBq4MKeFohLN se9vkXffORTpe7B6oXlOaOmqJymSNFFv4dRIj60IEt72I2IeBk/IvDWMVizNFDhsiwG5 oLXoX8v8/D2TR3VchcPU6NnGA8Tz4xUulr8CGM0bH4JpxJC+rwQKPCKIOXDCSfZuL8TH qh1O0Y1EmVhZWvHANzS9OqHIAZYTb95Lf4Rpb274mpmOk9ImXhqXRWF+veCHNS4TJDNr L8CQ== X-Gm-Message-State: APjAAAX+u8+eRMzaDTAswQaeJGMrJ1KHDNgNcCa93rCiJMzjnyMgNqkg EWm68+TXcp870pHPnZXoRiv3ZA== X-Google-Smtp-Source: APXvYqyIMDoQlsl43QCNsVhRYXpoYITg5VIfY+O2wLl8i+CLi7wPBZ/xxHMFQvzgoHS6cWZ48vXyxQ== X-Received: by 2002:a5e:8417:: with SMTP id h23mr4407052ioj.17.1580398171787; Thu, 30 Jan 2020 07:29:31 -0800 (PST) Received: from [192.168.1.159] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id z8sm1958345ilk.9.2020.01.30.07.29.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 30 Jan 2020 07:29:31 -0800 (PST) Subject: Re: IORING_REGISTER_CREDS[_UPDATE]() and credfd_create()? To: Christian Brauner Cc: Jann Horn , Stefan Metzmacher , io-uring , Linux API Mailing List , Pavel Begunkov References: <1ac31828-e915-6180-cdb4-36685442ea75@kernel.dk> <0d4f43d8-a0c4-920b-5b8f-127c1c5a3fad@kernel.dk> <4f833fc5-b4c0-c304-c3c2-f63c050b90a2@kernel.dk> <9ce2e571-ed84-211a-4e99-d830ecdaf0e2@kernel.dk> <20200130102635.ar2bohr7n4li2hyd@wittgenstein> <20200130151342.u554shnaliau42jq@wittgenstein> From: Jens Axboe Message-ID: Date: Thu, 30 Jan 2020 08:29:30 -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: <20200130151342.u554shnaliau42jq@wittgenstein> 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 1/30/20 8:13 AM, Christian Brauner wrote: > On Thu, Jan 30, 2020 at 07:11:08AM -0700, Jens Axboe wrote: >> On 1/30/20 3:26 AM, Christian Brauner wrote: >>> On Thu, Jan 30, 2020 at 11:11:58AM +0100, Jann Horn wrote: >>>> On Thu, Jan 30, 2020 at 2:08 AM Jens Axboe wrote: >>>>> On 1/29/20 10:34 AM, Jens Axboe wrote: >>>>>> On 1/29/20 7:59 AM, Jann Horn wrote: >>>>>>> On Tue, Jan 28, 2020 at 8:42 PM Jens Axboe wrote: >>>>>>>> On 1/28/20 11:04 AM, Jens Axboe wrote: >>>>>>>>> On 1/28/20 10:19 AM, Jens Axboe wrote: >>>>>>> [...] >>>>>>>>>> #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 didn't like it becoming a bit too complicated, both in terms of >>>>>>>> implementation and use. And the fact that we'd have to jump through >>>>>>>> hoops to make this work for a full chain. >>>>>>>> >>>>>>>> So I punted and just added sqe->personality and IOSQE_PERSONALITY. >>>>>>>> This makes it way easier to use. Same branch: >>>>>>>> >>>>>>>> https://git.kernel.dk/cgit/linux-block/log/?h=for-5.6/io_uring-vfs-creds >>>>>>>> >>>>>>>> I'd feel much better with this variant for 5.6. >>>>>>> >>>>>>> Some general feedback from an inspectability/debuggability perspective: >>>>>>> >>>>>>> At some point, it might be nice if you could add a .show_fdinfo >>>>>>> handler to the io_uring_fops that makes it possible to get a rough >>>>>>> overview over the state of the uring by reading /proc/$pid/fdinfo/$fd, >>>>>>> just like e.g. eventfd (see eventfd_show_fdinfo()). It might be >>>>>>> helpful for debugging to be able to see information about the fixed >>>>>>> files and buffers that have been registered. Same for the >>>>>>> personalities; that information might also be useful when someone is >>>>>>> trying to figure out what privileges a running process actually has. >>>>>> >>>>>> Agree, that would be a very useful addition. I'll take a look at it. >>>>> >>>>> Jann, how much info are you looking for? Here's a rough start, just >>>>> shows the number of registered files and buffers, and lists the >>>>> personalities registered. We could also dump the buffer info for >>>>> each of them, and ditto for the files. Not sure how much verbosity >>>>> is acceptable in fdinfo? >>>> >>>> At the moment, I personally am just interested in this from the >>>> perspective of being able to audit the state of personalities, to make >>>> important information about the security state of processes visible. >>>> >>>> Good point about verbosity in fdinfo - I'm not sure about that myself either. > > Afaik, there's no rule here. I would expect that it shouldn't exceed > 4096kb just because that is the limit that seems to be enforced for > writes to proc files atm; other than that it should be the wild west. > The fdinfo files are mostly interesting for anon_inode fds imho and the > ones that come to mind right now simply don't have a lot of information > to provide: > > eventfd > timerfd > seccomp_notify_fd > > Potentially, the mount fds from David could be extended in the future. 4MB is huge, I'd not get anywhere near that. So I'd say the current format is probably fine. I honed it a little bit to be prettier, looks good to me. I'll send it out for review. > (Side note: One thing that comes to mind is that we should probably > enforce^Wdocument that all fdinfo files use CamelCase?) Fine with me, seems to already be the norm, would be nice to have it documented. -- Jens Axboe