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=-8.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, 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 4CB05C4727F for ; Tue, 22 Sep 2020 06:32:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 06EC523A9C for ; Tue, 22 Sep 2020 06:32:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="HaQCQALG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729176AbgIVGco (ORCPT ); Tue, 22 Sep 2020 02:32:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48616 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726898AbgIVGcn (ORCPT ); Tue, 22 Sep 2020 02:32:43 -0400 Received: from mail-wr1-x444.google.com (mail-wr1-x444.google.com [IPv6:2a00:1450:4864:20::444]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 85CE8C061755; Mon, 21 Sep 2020 23:32:43 -0700 (PDT) Received: by mail-wr1-x444.google.com with SMTP id s12so15689127wrw.11; Mon, 21 Sep 2020 23:32:43 -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=eDOz/JMLknkTw9g+y5dhApSm97qkVUEs/ZHTL0gz2fw=; b=HaQCQALGHVNQEMfZjWIQPSNwZdZYY918PSJxIKXBtHGREzrfZs14l3A7EVqs2FMev/ IJEb11WYJ0Io7OvlAVv0yN7wti4dY6131+xDOqnq33+mYC8No5DoDKBA0p28miZblzSh iNg4UEEi1t4FGDg7qM28k8HJWOiayhzucNTCXz50wqRizN5pQgGXudx9Eg67GPANhr56 mEa26Q61i7gAReMjuCfJwAh+HVaTrMT52kQoueu+Kbqdewu6qCadAh37ghukc7GFxD1C O0B5pJecQysUZMJL8izt5QrVScpa7C7bG8FE9jy6GPyeF/acFygKkym3brbq6FgSx5HG wh1w== 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=eDOz/JMLknkTw9g+y5dhApSm97qkVUEs/ZHTL0gz2fw=; b=Axole8VmCQWtxzHLCme95aa2gjvpwCeAqQ/XplPdXWi9n9Fq8DufMbCjLqXf5ZfTtO Ch8tlHpb2sL1gQXm58m21ZO/davJUmJDN0xo7DerDQBFswX3WiLct+Wkv6EFgFETfPRe ELQ5iaTNhTj/TCCYdsvYubqWqMZ1EUMopOMgcxeLLrt9uNa95+0rAA1Bf685XRPVKlRz q/gzLtocacn9F8pNtAvlwDQ+8XvEn0tydk+QGFiCejguPN7WJbLJfqPUNvjQm95wkaTc enrT+GO9dL/RT3RD3IFYoFdFjWhDyCPjq/KyBtycJKFYE9JC2YRNUT6uVFYGlfgNwkPY HaDg== X-Gm-Message-State: AOAM5319ax/wOO1qbckVBBZwPS6hA56KhtDH0tdIUbSZsXuL+6nVvtbY kRevcHEenz3p2xAxeUBBOG08goVq8kIyog== X-Google-Smtp-Source: ABdhPJzC1rbzyPo53+fNSxXWPDaZOzMzgC1GT/88osu+za3TOCt7+Tr5Ya9aJiKtMy5iRtpQZlj3MQ== X-Received: by 2002:adf:fa52:: with SMTP id y18mr3532704wrr.264.1600756361855; Mon, 21 Sep 2020 23:32:41 -0700 (PDT) Received: from [192.168.43.240] ([5.100.192.97]) by smtp.gmail.com with ESMTPSA id d83sm3167538wmf.23.2020.09.21.23.32.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Sep 2020 23:32:41 -0700 (PDT) To: Andy Lutomirski Cc: Arnd Bergmann , Christoph Hellwig , Al Viro , Andrew Morton , Jens Axboe , David Howells , linux-arm-kernel , X86 ML , LKML , "open list:MIPS" , Parisc List , linuxppc-dev , linux-s390 , sparclinux , linux-block , Linux SCSI List , Linux FS Devel , linux-aio , io-uring@vger.kernel.org, linux-arch , Linux-MM , Network Development , keyrings@vger.kernel.org, LSM List References: <563138b5-7073-74bc-f0c5-b2bad6277e87@gmail.com> <486c92d0-0f2e-bd61-1ab8-302524af5e08@gmail.com> 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: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag Message-ID: Date: Tue, 22 Sep 2020 09:30:09 +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: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 22/09/2020 03:58, Andy Lutomirski wrote: > On Mon, Sep 21, 2020 at 5:24 PM Pavel Begunkov wrote: >>>>>>> Ah, so reading /dev/input/event* would suffer from the same issue, >>>>>>> and that one would in fact be broken by your patch in the hypothetical >>>>>>> case that someone tried to use io_uring to read /dev/input/event on x32... >>>>>>> >>>>>>> For reference, I checked the socket timestamp handling that has a >>>>>>> number of corner cases with time32/time64 formats in compat mode, >>>>>>> but none of those appear to be affected by the problem. >>>>>>> >>>>>>>> Aside from the potentially nasty use of per-task variables, one thing >>>>>>>> I don't like about PF_FORCE_COMPAT is that it's one-way. If we're >>>>>>>> going to have a generic mechanism for this, shouldn't we allow a full >>>>>>>> override of the syscall arch instead of just allowing forcing compat >>>>>>>> so that a compat syscall can do a non-compat operation? >>>>>>> >>>>>>> The only reason it's needed here is that the caller is in a kernel >>>>>>> thread rather than a system call. Are there any possible scenarios >>>>>>> where one would actually need the opposite? >>>>>>> >>>>>> >>>>>> I can certainly imagine needing to force x32 mode from a kernel thread. >>>>>> >>>>>> As for the other direction: what exactly are the desired bitness/arch semantics of io_uring? Is the operation bitness chosen by the io_uring creation or by the io_uring_enter() bitness? >>>>> >>>>> It's rather the second one. Even though AFAIR it wasn't discussed >>>>> specifically, that how it works now (_partially_). >>>> >>>> Double checked -- I'm wrong, that's the former one. Most of it is based >>>> on a flag that was set an creation. >>>> >>> >>> Could we get away with making io_uring_enter() return -EINVAL (or >>> maybe -ENOTTY?) if you try to do it with bitness that doesn't match >>> the io_uring? And disable SQPOLL in compat mode? >> >> Something like below. If PF_FORCE_COMPAT or any other solution >> doesn't lend by the time, I'll take a look whether other io_uring's >> syscalls need similar checks, etc. >> >> >> diff --git a/fs/io_uring.c b/fs/io_uring.c >> index 0458f02d4ca8..aab20785fa9a 100644 >> --- a/fs/io_uring.c >> +++ b/fs/io_uring.c >> @@ -8671,6 +8671,10 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit, >> if (ctx->flags & IORING_SETUP_R_DISABLED) >> goto out; >> >> + ret = -EINVAl; >> + if (ctx->compat != in_compat_syscall()) >> + goto out; >> + > > This seems entirely reasonable to me. Sharing an io_uring ring > between programs with different ABIs seems a bit nutty. > >> /* >> * For SQ polling, the thread will do all submissions and completions. >> * Just return the requested submit count, and wake the thread if >> @@ -9006,6 +9010,10 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p, >> if (ret) >> goto err; >> >> + ret = -EINVAL; >> + if (ctx->compat) >> + goto err; >> + > > I may be looking at a different kernel than you, but aren't you > preventing creating an io_uring regardless of whether SQPOLL is > requested? I diffed a not-saved file on a sleepy head, thanks for noticing. As you said, there should be an SQPOLL check. ... if (ctx->compat && (p->flags & IORING_SETUP_SQPOLL)) goto err; -- Pavel Begunkov