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=-5.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 38FA7C433EA for ; Mon, 20 Jul 2020 17:02:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0FE95206E9 for ; Mon, 20 Jul 2020 17:02:24 +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="VcHZcngk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733033AbgGTRCX (ORCPT ); Mon, 20 Jul 2020 13:02:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51744 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730871AbgGTRCW (ORCPT ); Mon, 20 Jul 2020 13:02:22 -0400 Received: from mail-il1-x144.google.com (mail-il1-x144.google.com [IPv6:2607:f8b0:4864:20::144]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 18856C0619D2 for ; Mon, 20 Jul 2020 10:02:22 -0700 (PDT) Received: by mail-il1-x144.google.com with SMTP id t27so13899601ill.9 for ; Mon, 20 Jul 2020 10:02:22 -0700 (PDT) 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=lLa51XHV19pSn8dCau2GuTKu0LZrcXv1DrhKxMQG6SQ=; b=VcHZcngkwm/n7gdBFYMeUsSdh5uZvMVcDjIBV3ECeQR8GAZCLzW/ix7cDJDD4mkw8j XvXBGxCga3mtMWCHZyakDM16MKnA20qLojDjxmaMOM2hAQFo3xkfcuygPVr3do95FJzw /iXRZJCdZkPfSkB027sq0tDcY4+Y38vvKTW4YXISYUWJRLtYsTQuEP1+Oc87ev80laL2 G+ZPldX2GCPKQ3LR3oUw2d1qiycFNcp19R40LW3VYX2NPOi3FQI7ZWFNsRui/BDnepP8 mnc7/F2Cq94AzCvhFEBa3icJeg/Eox3xAjWyP1BRBrgbuMzqTYQIPa05G9ZF9RHUN9aI BGqg== 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=lLa51XHV19pSn8dCau2GuTKu0LZrcXv1DrhKxMQG6SQ=; b=prh3OmOkJ6XkuZcW7hurVkNv5EsM7VTE9CMdMi9ZkuhMD/nFBL6IHfGaoHIRVTQXGi j7R8lRFKB7yoo9TlQP4SC9lb4/qKYycXPo9Ms58t21KXusrxnq2Nus133/kxcHtlXDLK 4a41cl2mINZs37MOFT/pxSSfqW2U2T/doK+MrOoP+j6rp68uXdRCm6RoDDBAA2eYAeAO yYBFMva2l/xnP66AGojUcyj3sJdAuTDcqKSvnAz8yOso7eXHWFEiKFK+/P68T6Gm2qEP YkKvfVvDZTa8gWeVc4jacZvGpUhQf4vR0gvVr1ZmVL8dCkZjMQ6yrzkFp13mSAGhtUXR gQZg== X-Gm-Message-State: AOAM532CacdwDj1EHQMeXz1dufYePMCe3rzcDY9FRUwjbSNoiDsKeJ8d MAPO1OOlyREmKS324IDiCYRIGQ== X-Google-Smtp-Source: ABdhPJz5zLxNXcsTdxphGCNjFI0YjQ5J7FtVKPPcrF4sltl8mBBoIBkKciDhL+q4GYsjdYBiefx/jQ== X-Received: by 2002:a92:c689:: with SMTP id o9mr24384488ilg.302.1595264541233; Mon, 20 Jul 2020 10:02:21 -0700 (PDT) Received: from [192.168.1.58] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id m2sm9126349iln.1.2020.07.20.10.02.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Jul 2020 10:02:20 -0700 (PDT) Subject: Re: io_uring vs in_compat_syscall() To: Andy Lutomirski Cc: Christoph Hellwig , linux-arch@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, io-uring@vger.kernel.org References: From: Jens Axboe Message-ID: Date: Mon, 20 Jul 2020 11:02:19 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On 7/20/20 10:58 AM, Andy Lutomirski wrote: > >> On Jul 20, 2020, at 9:37 AM, Jens Axboe wrote: >> >> On 7/20/20 12:10 AM, Christoph Hellwig wrote: >>> Hi Jens, >>> >>> I just found a (so far theoretical) issue with the io_uring submission >>> offloading to workqueues or threads. We have lots of places using >>> in_compat_syscall() to check if a syscall needs compat treatmenet. >>> While the biggest users is iocttl(), we also have a fair amount of >>> places using in_compat_task() in read and write methods, and these >>> will not do the wrong thing when used with io_uring under certain >>> conditions. I'm not sure how to best fix this, except for making sure >>> in_compat_syscall() returns true one way or another for these cases. >> >> We can probably propagate this information in the io_kiocb via a flag, >> and have the io-wq worker set TS_COMPAT if that's the case. >> > > Is TS_COMPAT actually a cross-arch concept for which this is safe? > Having a real arch helper for “set the current syscall arch for the > current kernel thread” seems more sensible to me. Sure, I'd consider that implementation detail for the actual patch(es) for this issue. -- Jens Axboe