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=-5.3 required=3.0 tests=BAYES_00, 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 B6A34C49EA5 for ; Thu, 24 Jun 2021 03:53:01 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1A633613C5 for ; Thu, 24 Jun 2021 03:53:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1A633613C5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 0D7118D0007; Wed, 23 Jun 2021 23:53:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0878B6B0099; Wed, 23 Jun 2021 23:53:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E6D638D0007; Wed, 23 Jun 2021 23:52:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0115.hostedemail.com [216.40.44.115]) by kanga.kvack.org (Postfix) with ESMTP id AF9686B0098 for ; Wed, 23 Jun 2021 23:52:59 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id E275718144D26 for ; Thu, 24 Jun 2021 03:52:59 +0000 (UTC) X-FDA: 78287246478.07.BF63838 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by imf30.hostedemail.com (Postfix) with ESMTP id EF117E000243 for ; Thu, 24 Jun 2021 03:52:58 +0000 (UTC) Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4G9R3P4xY6zZhXR; Thu, 24 Jun 2021 11:49:53 +0800 (CST) Received: from dggema756-chm.china.huawei.com (10.1.198.198) by dggemv704-chm.china.huawei.com (10.3.19.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Thu, 24 Jun 2021 11:52:55 +0800 Received: from [10.174.177.134] (10.174.177.134) by dggema756-chm.china.huawei.com (10.1.198.198) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Thu, 24 Jun 2021 11:52:54 +0800 Subject: Re: [BUG] arm64: an infinite loop in generic_perform_write() To: Matthew Wilcox CC: Mark Rutland , Andrew Morton , Stephen Rothwell , Al Viro , Randy Dunlap , "Catalin Marinas" , Will Deacon , Linux ARM , linux-mm , "open list" References: <20210623132223.GA96264@C02TD0UTHF1T.local> <1c635945-fb25-8871-7b34-f475f75b2caf@huawei.com> From: Chen Huang Message-ID: Date: Thu, 24 Jun 2021 11:52:53 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="gbk" X-Originating-IP: [10.174.177.134] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggema756-chm.china.huawei.com (10.1.198.198) X-CFilter-Loop: Reflected Authentication-Results: imf30.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=huawei.com; spf=pass (imf30.hostedemail.com: domain of chenhuang5@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=chenhuang5@huawei.com X-Stat-Signature: hoa9dch6o4nmk11s9aa9nhkruzgmgzdw X-Rspamd-Queue-Id: EF117E000243 X-Rspamd-Server: rspam06 X-HE-Tag: 1624506778-241597 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: =D4=DA 2021/6/24 11:24, Matthew Wilcox =D0=B4=B5=C0: > On Thu, Jun 24, 2021 at 11:10:41AM +0800, Chen Huang wrote: >> In userspace, I perform such operation: >> >> fd =3D open("/tmp/test", O_RDWR | O_SYNC); >> access_address =3D (char *)mmap(NULL, uio_size, PROT_READ, MAP= _SHARED, uio_fd, 0); >> ret =3D write(fd, access_address + 2, sizeof(long)); >=20 > ... you know that accessing this at unaligned offsets isn't going to > work. It's completely meaningless. Why are you trying to do it? > . >=20 Yeah, it's a wrong usage of access. But maybe it's still a problem an userspace operation makes the kernel crash.