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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 819E2C49EA6 for ; Thu, 24 Jun 2021 11:17:32 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2B62D611CE for ; Thu, 24 Jun 2021 11:17:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2B62D611CE Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 0AECF6B0036; Thu, 24 Jun 2021 07:17:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0864C6B005D; Thu, 24 Jun 2021 07:17:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E90116B006C; Thu, 24 Jun 2021 07:17:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0033.hostedemail.com [216.40.44.33]) by kanga.kvack.org (Postfix) with ESMTP id ABB5D6B0036 for ; Thu, 24 Jun 2021 07:17:30 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id D90578249980 for ; Thu, 24 Jun 2021 11:17:30 +0000 (UTC) X-FDA: 78288366660.26.DFEC2D2 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf17.hostedemail.com (Postfix) with ESMTP id A85B240002C1 for ; Thu, 24 Jun 2021 11:17:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=cfReeu0dJKzIeg2BgFYSOkZyK6s3mc3KPP/KhBuenyY=; b=lO3x15aO+H8qwI+t//6WYC7WHl RiKchv9n3r6OLd5/pgJ7D1tuZ6EQApIuH0qxL3ElTsS81IwkLNx4341XVBmK43GYpKP7whoRHJ+SS VDW2/x4doJcJ9mfCRUAeo4scbtDPzG907T41Vt6iegiLQXukyblzsQV8giGHeMCDDL3hZBtuzbhgy dguiNavnzYMI1cLmqywlC9+t5nN3m3Y7iuXVWkLofYfv033zhDCA0zbqTTF/ysSBEpySjbCfysbtV HOZXC1NkeT8x/38WqchMcFMR7Q7WUuN/cAtcDy6ZxxA27aUsymihPDj9ICe65lumVAl/fjAsB/wEf uQbf292w==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1lwNKl-00GVCu-09; Thu, 24 Jun 2021 11:15:59 +0000 Date: Thu, 24 Jun 2021 12:15:46 +0100 From: Matthew Wilcox To: Christoph Hellwig Cc: Chen Huang , Mark Rutland , Andrew Morton , Stephen Rothwell , Al Viro , Randy Dunlap , Catalin Marinas , Will Deacon , Linux ARM , linux-mm , open list Subject: Re: [BUG] arm64: an infinite loop in generic_perform_write() Message-ID: References: <20210623132223.GA96264@C02TD0UTHF1T.local> <1c635945-fb25-8871-7b34-f475f75b2caf@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=lO3x15aO; spf=none (imf17.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none X-Stat-Signature: uxbzhdp9md9q149jeksi5hggys4pyjcq X-Rspamd-Queue-Id: A85B240002C1 X-Rspamd-Server: rspam06 X-HE-Tag: 1624533449-787502 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: On Thu, Jun 24, 2021 at 08:04:07AM +0100, Christoph Hellwig wrote: > On Thu, Jun 24, 2021 at 04:24:46AM +0100, Matthew Wilcox wrote: > > On Thu, Jun 24, 2021 at 11:10:41AM +0800, Chen Huang wrote: > > > In userspace, I perform such operation: > > > > > > fd = open("/tmp/test", O_RDWR | O_SYNC); > > > access_address = (char *)mmap(NULL, uio_size, PROT_READ, MAP_SHARED, uio_fd, 0); > > > ret = write(fd, access_address + 2, sizeof(long)); > > > > ... you know that accessing this at unaligned offsets isn't going to > > work. It's completely meaningless. Why are you trying to do it? > > We still should not cause an infinite loop in kernel space due to a > a userspace programmer error. They're running as root and they've mapped some device memory. We can't save them from themself. Imagine if they'd done this to the NVMe BAR.