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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 12900C2D0DB for ; Wed, 29 Jan 2020 17:46:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC591206F0 for ; Wed, 29 Jan 2020 17:46:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="D37nBQNH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727290AbgA2RqV (ORCPT ); Wed, 29 Jan 2020 12:46:21 -0500 Received: from mail-lj1-f169.google.com ([209.85.208.169]:43543 "EHLO mail-lj1-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726679AbgA2RqV (ORCPT ); Wed, 29 Jan 2020 12:46:21 -0500 Received: by mail-lj1-f169.google.com with SMTP id a13so244189ljm.10; Wed, 29 Jan 2020 09:46:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=QS9r6Pw3kjijpdm49BCeHOyhsA9XNtzwCyIFlvRSyMA=; b=D37nBQNH5impZ1FUQu16DzoaBYe3rJPpMMnFn99HZRX9UW0t4Mrd1bcrtwe0/KcQAn +cwe+VQ1cu66lN4Fvw9sZOITgrNIWmH6zHRjvQJZkpZlLhrzmLlZohn5cSmRYCg6fvjc /6I0ZX3OfvEJCUSVb6WveDRs7BkVSuaNbTLcFyqtyUFCj026BvIi/DuZlD0n1gIss3KI JDhY3TaxASaScAVqOsEfAXmuSZ4qEeB9GIT6Ui2njBRRL3fMwVQv7b1oDo87JtccNMeA dGC85wS+dRCXQe45uZBhy61Chwj+WsoJdOOB2FL7yHSDD65kg+L24jY+9B7Z91fGWv4E NLZQ== 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=QS9r6Pw3kjijpdm49BCeHOyhsA9XNtzwCyIFlvRSyMA=; b=TeUID1nHpgxZcSsc67Qp0XIRak+WGJUSIFr+qjll2UBM3feXz5qNj8nNbu6zU993Uo I9MnrusdZ/J/8au5EhD8EJGlaQvg+udb5sUqPgJ2jfFplZDuJWCE37urfyGASLwp6atz KLre0ZCWaJEspc1YjenwSdOMosp2t5fx0PW35sGUbV752RojCu7V0di8NUPa7XgQ8kQi NbGdV4l9JoygFpOG4DWVXfsGci/LDzoaRQ8MfYrhVHscmP0wlHLBWotHCVOjfyNFd08f +fvUzmih8kHlqGwrX7bKzS64GA0wawyyY2azTyMrRioEolsLyMX/VaGfpJkTCLYhKcHY VY5w== X-Gm-Message-State: APjAAAXWdTr7lppT0sfL4zJ73iiwj3wXnrCHPJU5h8vyqnDb2QVFtSww KlWk7HaW4LaD7uqL/WUB99m3FgEl5Fs= X-Google-Smtp-Source: APXvYqxCiKlvgF9UCVjzi1PsVxKNsiV6KSf8cb1GHAGKwOUPpNLNULgLRDS2kJ+Pc/xrYP0X5atHwQ== X-Received: by 2002:a2e:3504:: with SMTP id z4mr145824ljz.273.1580319978398; Wed, 29 Jan 2020 09:46:18 -0800 (PST) Received: from [172.31.190.83] ([86.57.146.226]) by smtp.gmail.com with ESMTPSA id z205sm1366096lfa.52.2020.01.29.09.46.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Jan 2020 09:46:17 -0800 (PST) Subject: Re: IORING_REGISTER_CREDS[_UPDATE]() and credfd_create()? To: Jens Axboe , Stefan Metzmacher Cc: io-uring , Linux API Mailing List References: <688e187a-75dd-89d9-921c-67de228605ce@samba.org> <1ac31828-e915-6180-cdb4-36685442ea75@kernel.dk> <0d4f43d8-a0c4-920b-5b8f-127c1c5a3fad@kernel.dk> <2d7e7fa2-e725-8beb-90b9-6476d48bdb33@gmail.com> <6c401e23-de7c-1fc1-4122-33d53fcf9700@kernel.dk> <35eebae7-76dd-52ee-58b2-4f9e85caee40@kernel.dk> <6e5ab6bf-6ff1-14df-1988-a80a7c6c9294@gmail.com> <2019e952-df2a-6b57-3571-73c525c5ba1a@kernel.dk> <0df4904f-780b-5d5f-8700-41df47a1b470@kernel.dk> <5406612e-299d-9d6e-96fc-c962eb93887f@gmail.com> <821243e7-b470-ad7a-c1a5-535bee58e76d@samba.org> <9a419bc5-4445-318d-87aa-1474b49266dd@gmail.com> <40d52623-5f9c-d804-cdeb-b7da6b13cb4f@samba.org> <3e1289de-8d8e-49cf-cc9f-fb7bc67f35d5@gmail.com> <9aef3b3b-7e71-f7f1-b366-2517b4d52719@kernel.dk> From: Pavel Begunkov Message-ID: Date: Wed, 29 Jan 2020 20:46:16 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.4.2 MIME-Version: 1.0 In-Reply-To: <9aef3b3b-7e71-f7f1-b366-2517b4d52719@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 1/29/2020 8:34 PM, Jens Axboe wrote: > On 1/29/20 7:23 AM, Pavel Begunkov wrote: >>>>> The override_creds(personality_creds) has changed current->cred >>>>> and get_current_cred() will just pick it up as in the default case. >>>>> >>>>> This would make the patch much simpler and allows put_cred() to be >>>>> in io_put_work() instead of __io_req_aux_free() as explained above. >>>>> >>>> >>>> It's one extra get_current_cred(). I'd prefer to find another way to >>>> clean this up. >>> >>> As far as I can see it avoids a get_cred() in the IOSQE_PERSONALITY case >>> and the if (!req->work.creds) for both cases. >> >> Great, that you turned attention to that! override_creds() is already >> grabbing a ref, so it shouldn't call get_cred() there. >> So, that's a bug. > > It's not though - one is dropped in that function, the other when the > request is freed. So we do need two references to it. With the proposed > change to keep the override_creds() variable local for that spot we > don't, and the get_cred() can then go. You're right here. It seems, it was too much looking at the same code :) > >> It could be I'm wrong with the statement above, need to recheck all this >> code to be sure. > > I think you are :-) Considering above, there shouldn't be much difference indeed. One extra rcu_dereference() in get_current_creds() instead of get_cred(), but that's nothing. Later we can hide one get by using submission state from the long patchset, I sent a while ago. > >> BTW, io_req_defer_prep() may be called twice for a req, so you will >> reassign it without putting a ref. It's safer to leave NULL checks. At >> least, until I've done reworking and fixing preparation paths. > > Agree, the NULL checks are safer and we should keep them. > > Going through the rest of this thread, I'm making the following changes: > > - ID must be > 0. I like that change, as we don't need an sqe flag to > select personality then, and it also makes it obvious that id == 0 is > just using current creds. > > - Fixed the missing put_cred() in the teardown > > - Use a local variable in io_submit_sqe() instead of assigning the > creds to req->work.creds there > > - Use cyclic idr allocation > > I'm going to fold in as appropriate. If there are fixes needed on top of > that, let's do them separately. > -- Pavel Begunkov