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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 6C560C432C3 for ; Mon, 25 Nov 2019 00:43:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 404D420748 for ; Mon, 25 Nov 2019 00:43:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727085AbfKYAnl convert rfc822-to-8bit (ORCPT ); Sun, 24 Nov 2019 19:43:41 -0500 Received: from smtpbg505.qq.com ([203.205.250.114]:53409 "EHLO smtpbg.qq.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726865AbfKYAnk (ORCPT ); Sun, 24 Nov 2019 19:43:40 -0500 X-QQ-mid: Xesmtp2t1574642607tdv42jxil Received: from [172.16.31.194] (unknown [218.76.23.26]) by esmtp4.qq.com (ESMTP) with id ; Mon, 25 Nov 2019 08:43:25 +0800 (CST) X-QQ-SSF: 00000000000000B0SF101F00000000K X-QQ-FEAT: WLyAQnF3LFnjUUHz7YtoXaubmctqYYApjTsU/aMmSXVABhv/nKTQIM97PHLrd xws7umg3B2+XaIrSziC2jg/n0ZdDsG25VcUjNtxi2SQo2P+dkb4kk+SRe7mihArNt/2DAp0 RAfWkAQ/KqkL+wtKArBfbrSNg4Hi8Mu1IfjsbxYDsz0ji4oVyUSXrHsMcEQF6EZVTbeLwch +iGdKPsrq/N0gyF1VdbrBubErP9Gqv5cI2kKJVyEAfFGhvB1awtAoR1xVYBHAa4cwmE8Hjb WvVOZSRQrIKvvKZeTHHb1bR5ZvIAn5qnoC1DFnd1k9Xng3W48joTm7Ph4= X-QQ-GoodBg: 0 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 13.0 \(3601.0.10\)) Subject: Re: [PATCH v2] io_uring: fix dead-hung for non-iter fixed rw From: Jackie Liu In-Reply-To: Date: Mon, 25 Nov 2019 08:43:23 +0800 Cc: Jens Axboe , io-uring@vger.kernel.org Content-Transfer-Encoding: 8BIT Message-Id: References: <620023b272fef0fd76d0f91ff1876fa64864caa6.1574585281.git.asml.silence@gmail.com> <6a2fcf67-1267-a02a-98ce-435bbb2ca9bb@kernel.dk> To: Pavel Begunkov X-Mailer: Apple Mail (2.3601.0.10) X-QQ-SENDSIZE: 520 Feedback-ID: Xesmtp:byteisland.com:bgweb:bgweb1 Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org > 2019年11月25日 01:52，Pavel Begunkov 写道： > > On 24/11/2019 20:10, Jens Axboe wrote: >> On 11/24/19 1:58 AM, Pavel Begunkov wrote: >>> Read/write requests to devices without implemented read/write_iter >>> using fixed buffers causes general protection fault, which totally >>> hangs a machine. >>> >>> io_import_fixed() initialises iov_iter with bvec, but loop_rw_iter() >>> accesses it as iovec, so dereferencing random address. >>> >>> kmap() page by page in this case >> >> This looks good to me, much cleaner/simpler. I've added a few pipe fixed >> buffer tests to liburing as well. Didn't crash for me, but obvious >> garbage coming out. I've flagged this for stable as well. >> > The problem I have is that __user pointer is meant to be checked > for not being a kernel address. I suspect, it could fail in some > device, which double checks the pointer after vfs (e.g. using access_ok()). > Am I wrong? Not a fault at least... > > #define access_ok(...) __range_not_ok(addr, user_addr_max()); > > BTW, is there anybody testing it for non x86-64 arch? > I have some aarch64 platform, What test do you want me to do? -- Jackie Liu