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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 7C24CC433DF for ; Fri, 12 Jun 2020 19:20:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 53404206D7 for ; Fri, 12 Jun 2020 19:20:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="DsUa9RpV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726384AbgFLTUd (ORCPT ); Fri, 12 Jun 2020 15:20:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44374 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726376AbgFLTUc (ORCPT ); Fri, 12 Jun 2020 15:20:32 -0400 Received: from mail-wr1-x441.google.com (mail-wr1-x441.google.com [IPv6:2a00:1450:4864:20::441]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4E79C03E96F; Fri, 12 Jun 2020 12:20:31 -0700 (PDT) Received: by mail-wr1-x441.google.com with SMTP id x14so10909165wrp.2; Fri, 12 Jun 2020 12:20:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=to:cc:references:from:autocrypt:subject:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=LuXcbBtMwnamBPCkX1sG4sng+tF/heSnrzHbTXFtj4s=; b=DsUa9RpV8L9CWdpiI+BPNTZXCePK54aFjub3ZKf2TOJchFwa9NIQGSb4JXdScKTrMk wjSwX+aoHiSrnvefxcN2UwsXmokYoj0xkPpbxs5rODMHjF9Z0+cgNs5LXqYWTI33NwAg NWDJSLVArr40a9ocogLX/KXzbHv6IML1V01voQM5iR8fB5LhW4Q0MbN9kfMBz4ipcUVv UT3QzwczIXoLeLXhW7/r8PRleQmlRBubOL0aXyBdaGHDLM2JlNow6dliuD1+Azr3dM4R xf4lmpRqobpOn6lYjF84tfLYVrRUjzpIFY6sEyO+GF690soLIoz9qUtqy6kqsGsV4tI5 rFuA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:cc:references:from:autocrypt:subject :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=LuXcbBtMwnamBPCkX1sG4sng+tF/heSnrzHbTXFtj4s=; b=rWOP1l5iisHaatoiixa2vrlbLW6u8YMp5qoqle2WAEWlw9IHCkILmlmYEahj+2LNuY 9Ab5Vf361a+OH4t7JsYxXnJXgzt8fh7lwpDaTIbO72gWgOaTi6rZAPtZR425bB95Ae/b OqmKWFH/4pGQZ7VJd2Q7hF1eXnvZAfBGUkcp3fdHrg/CpSrqW3fP4KO7Q3BW5C2ARd5h QuJ0snP+LMlDHn0dEQVCzD8OfJF07Panl9rLPokS6ywp56VZ9ukzKPcvQBVgK/dndif9 NlWacbN5qAkHMiAMUog0qgtfOdaFYPbKa6+65WliKdGuZG3HhELgJJ/kF6V2bTBsPof7 mo7w== X-Gm-Message-State: AOAM531rW8BS8wbI66TD/7hqmeJEp45qNvTT2wEMSJ1OWGZv8v/yjhga c0xFPlJUtEfTEaDGlxPmGz9CImEs X-Google-Smtp-Source: ABdhPJwv7pPerDrvRvRngvNqO7wz80usFRNkJwzS7W+COM5DR8YBEBuRwZ1OWHPx2+vIVGjUl6TQsg== X-Received: by 2002:a1c:b703:: with SMTP id h3mr385091wmf.81.1591989629779; Fri, 12 Jun 2020 12:20:29 -0700 (PDT) Received: from [192.168.43.114] ([5.100.193.151]) by smtp.gmail.com with ESMTPSA id e12sm11581250wro.52.2020.06.12.12.20.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 12 Jun 2020 12:20:28 -0700 (PDT) To: "Eric W. Biederman" , Jens Axboe Cc: linux-kernel@vger.kernel.org, io-uring@vger.kernel.org References: <87a71jjbzr.fsf@x220.int.ebiederm.org> 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== Subject: Re: io_wq_work task_pid is nonsense Message-ID: Date: Fri, 12 Jun 2020 22:19:05 +0300 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: <87a71jjbzr.fsf@x220.int.ebiederm.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 04/06/2020 14:39, Eric W. Biederman wrote: > I was looking at something else and I happened to come across the > task_pid field in struct io_wq_work. The field is initialized with > task_pid_vnr. Then it is used for cancelling pending work. > > The only appropriate and safe use of task_pid_vnr is for sending > a pid value to userspace and that is not what is going on here. > > This use is particularly bad as it looks like I can start a pid > namespace create an io work queue and create threads that happen to have > the userspace pid in question and then terminate them, or close their > io_work_queue file descriptors, and wind up closing someone else's work. > > There is also pid wrap around, and the craziness of de_thread to contend > with as well. Thanks reporting about this. It's not as bad because it's limited to a single io_uring instance and is more like precautions. False positives should be handled in userspace. > Perhaps since all the task_pid field is used for is cancelling work for > an individual task you could do something like the patch below. I am > assuming no reference counting is necessary as the field can not live > past the life of a task. > > Of cource the fact that you don't perform this work for file descriptors > that are closed just before a task exits makes me wonder. > > Can you please fix this code up to do something sensible? > Maybe like below? I'll deal with it. Needs a bit extra to not screw work->task refcounting, but the idea looks right. > > Eric > > diff --git a/fs/io-wq.h b/fs/io-wq.h > index 5ba12de7572f..bef29fff7403 100644 > --- a/fs/io-wq.h > +++ b/fs/io-wq.h > @@ -91,7 +91,7 @@ struct io_wq_work { > const struct cred *creds; > struct fs_struct *fs; > unsigned flags; > - pid_t task_pid; > + struct task_struct *task; > }; > > #define INIT_IO_WORK(work, _func) \ > @@ -129,7 +129,7 @@ static inline bool io_wq_is_hashed(struct io_wq_work *work) > > void io_wq_cancel_all(struct io_wq *wq); > enum io_wq_cancel io_wq_cancel_work(struct io_wq *wq, struct io_wq_work *cwork); > -enum io_wq_cancel io_wq_cancel_pid(struct io_wq *wq, pid_t pid); > +enum io_wq_cancel io_wq_cancel_task(struct io_wq *wq, struct task_struct *task); > > typedef bool (work_cancel_fn)(struct io_wq_work *, void *); > > diff --git a/fs/io-wq.c b/fs/io-wq.c > index 4023c9846860..2139a049d548 100644 > --- a/fs/io-wq.c > +++ b/fs/io-wq.c > @@ -1004,18 +1004,16 @@ enum io_wq_cancel io_wq_cancel_work(struct io_wq *wq, struct io_wq_work *cwork) > return io_wq_cancel_cb(wq, io_wq_io_cb_cancel_data, (void *)cwork); > } > > -static bool io_wq_pid_match(struct io_wq_work *work, void *data) > +static bool io_wq_task_match(struct io_wq_work *work, void *data) > { > - pid_t pid = (pid_t) (unsigned long) data; > + struct task_struct *task = data; > > - return work->task_pid == pid; > + return work->task == task; > } > > -enum io_wq_cancel io_wq_cancel_pid(struct io_wq *wq, pid_t pid) > +enum io_wq_cancel io_wq_cancel_task(struct io_wq *wq, struct task_struct *task) > { > - void *data = (void *) (unsigned long) pid; > - > - return io_wq_cancel_cb(wq, io_wq_pid_match, data); > + return io_wq_cancel_cb(wq, io_wq_task_match, task); > } > > struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data) > diff --git a/fs/io_uring.c b/fs/io_uring.c > index c687f57fb651..b9d557a21a26 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -1031,8 +1031,8 @@ static inline void io_req_work_grab_env(struct io_kiocb *req, > } > spin_unlock(¤t->fs->lock); > } > - if (!req->work.task_pid) > - req->work.task_pid = task_pid_vnr(current); > + if (!req->work.task) > + req->work.task = current; > } > > static inline void io_req_work_drop_env(struct io_kiocb *req) > @@ -7421,7 +7421,7 @@ static int io_uring_flush(struct file *file, void *data) > * If the task is going away, cancel work it may have pending > */ > if (fatal_signal_pending(current) || (current->flags & PF_EXITING)) > - io_wq_cancel_pid(ctx->io_wq, task_pid_vnr(current)); > + io_wq_cancel_task(ctx->io_wq, current); > > return 0; > } > -- Pavel Begunkov