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=-5.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 512A9C388F7 for ; Thu, 5 Nov 2020 20:38:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DF0B72073A for ; Thu, 5 Nov 2020 20:38:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Tgw7tRDa" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728137AbgKEUi3 (ORCPT ); Thu, 5 Nov 2020 15:38:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46098 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726729AbgKEUi3 (ORCPT ); Thu, 5 Nov 2020 15:38:29 -0500 Received: from mail-wm1-x329.google.com (mail-wm1-x329.google.com [IPv6:2a00:1450:4864:20::329]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0FD55C0613CF for ; Thu, 5 Nov 2020 12:38:29 -0800 (PST) Received: by mail-wm1-x329.google.com with SMTP id h22so2903974wmb.0 for ; Thu, 05 Nov 2020 12:38:28 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:references:from:autocrypt:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=uk52j9FM+zh7xdAxAamDg1vHHwbAVzJovEsR/zqEKe0=; b=Tgw7tRDao2/+JYbNdsL1ogUR8McWKfkCiQyw+LogECW8vVwnwtSkrDaRdVjW2rDrSC CVVPTD7O1DeLPMD3yG9+tB/HJGHOEaIiV5Eap4HZq829T98f3hJavxgQyvi6GI2K0BcZ HktZdt0wAdXgNnJpetT6hFRt7xv4HPzTOSx4UrW+76pTO/a4Cs0iMKlgSizYn8uB8QoU IBsxWMvjgEXDRkF3XjJtI63SEdg87eb5GsrL4qmmwMZTqI3AmIIloutIaspBCSRGGyAp xDiuMxeqeQWfpbumKMflYKSmewFTw0maesd/9CgZPKgJd4hR4WftTkSy+/nBc3jG+Yh7 N0Mw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:autocrypt:message-id :date:user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=uk52j9FM+zh7xdAxAamDg1vHHwbAVzJovEsR/zqEKe0=; b=Xw14G65K6WTlm3bUg1jiYJggat0Zo3L4ubrMOlWVrC1eBr4JgPYuQZg2LUiCEP2QEk m1e/ri16Mnxal7T8qnJsfG5YYVo2jdBPg9I0NHtaF2fYeBBdViY1hoI4qd9DcAxbXz6V Un2WCClmNd2hXlieU7zuBTCQiQlCgRGHoTObqW2jaMW1IvFFikWepYPiBn5qUCiWy3Kr d6VHfxBvQvEuyHll0F2pBq8TIAMJHbqVm6/m5/ZNuZeKDunGMBCm+p79WsQuGnto/WKA HQjxzdOgubci56uJcfZhCc8pF+vgYMLL2PQNsCU86VQ5kDpjxdouxexhOooUL0g9p05c FkOw== X-Gm-Message-State: AOAM530VCyObvklDjB6tCCPTEy2L+u2DQcwAy8qx1OqOnYCh+IfNglTf n2qj+5l6B3q6cda7WiFGX/9iHElQ/Zc= X-Google-Smtp-Source: ABdhPJwRfG3l1oE5brzYvE6tm2tRPQY8XkBXGCyCAxpcHKauR2ImWI8ad6HQMQNvOEfar7yU+4oGOQ== X-Received: by 2002:a1c:f20d:: with SMTP id s13mr4844852wmc.156.1604608707489; Thu, 05 Nov 2020 12:38:27 -0800 (PST) Received: from [192.168.1.47] (host109-152-100-228.range109-152.btcentralplus.com. [109.152.100.228]) by smtp.gmail.com with ESMTPSA id g131sm4099106wma.35.2020.11.05.12.38.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Nov 2020 12:38:26 -0800 (PST) Subject: Re: Use of disowned struct filename after 3c5499fa56f5? To: Jens Axboe , Dmitry Kadashev , io-uring@vger.kernel.org References: <1c1cd326-d99a-b15b-ab73-d5ee437db0fa@gmail.com> <7db39583-8839-ac9e-6045-5f6e2f4f9f4b@gmail.com> <97810ccb-2f85-9547-e7c1-ce1af562924d@kernel.dk> <38141659-e902-73c6-a320-33b8bf2af0a5@gmail.com> <361ab9fb-a67b-5579-3e7b-2a09db6df924@kernel.dk> From: Pavel Begunkov Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Message-ID: <9b52b4b1-a243-4dc0-99ce-d6596ca38a58@gmail.com> Date: Thu, 5 Nov 2020 20:35:26 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <361ab9fb-a67b-5579-3e7b-2a09db6df924@kernel.dk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 05/11/2020 20:26, Jens Axboe wrote: > On 11/5/20 1:04 PM, Pavel Begunkov wrote: >> On 05/11/2020 19:37, Jens Axboe wrote: >>> On 11/5/20 7:55 AM, Pavel Begunkov wrote: >>>> On 05/11/2020 14:22, Pavel Begunkov wrote: >>>>> On 05/11/2020 12:36, Dmitry Kadashev wrote: >>>> Hah, basically filename_parentat() returns back the passed in filename if not >>>> an error, so @oldname and @from are aliased, then in the end for retry path >>>> it does. >>>> >>>> ``` >>>> put(from); >>>> goto retry; >>>> ``` >>>> >>>> And continues to use oldname. The same for to/newname. >>>> Looks buggy to me, good catch! >>> >>> How about we just cleanup the return path? We should only put these names >>> when we're done, not for the retry path. Something ala the below - untested, >>> I'll double check, test, and see if it's sane. >> >> Retry should work with a comment below because it uses @oldname >> knowing that it aliases to @from, which still have a refcount, but I >> don't like this implicit ref passing. If someone would change >> filename_parentat() to return a new filename, that would be a nasty >> bug. > > Not a huge fan of how that works either, but I'm not in this to rewrite > namei.c... There are 6 call sites including do_renameat2(), a separate patch would change just ~15-30 lines, doesn't seem like a big rewrite. > >> options I see >> 1. take a reference on old/newname in the beginning. >> >> 2. don't return a filename from filename_parentat(). >> struct filename *name = ...; >> int ret = filename_parentat(name, ...); >> // use @name >> >> 3. (also ugly) >> retry: >> oldname = from; > > Not sure I follow - oldname == from, unless there's an error. Yes, this > depends on filename_parentat() returning oldname or IS_ERR(), but that's > how all the callers currently deal with it. I think it's more explicit but still ugly, let's forget about the third -- Pavel Begunkov