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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 AE4EEC433DF for ; Wed, 20 May 2020 11:13:31 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 827E2207D3 for ; Wed, 20 May 2020 11:13:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 827E2207D3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1BA7C900003; Wed, 20 May 2020 07:13:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 16A71900002; Wed, 20 May 2020 07:13:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0A6DA900003; Wed, 20 May 2020 07:13:31 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0064.hostedemail.com [216.40.44.64]) by kanga.kvack.org (Postfix) with ESMTP id E76E5900002 for ; Wed, 20 May 2020 07:13:30 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id AD083583C for ; Wed, 20 May 2020 11:13:30 +0000 (UTC) X-FDA: 76836836580.25.cow97_1e97e83ddbd2b X-HE-Tag: cow97_1e97e83ddbd2b X-Filterd-Recvd-Size: 1983 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf22.hostedemail.com (Postfix) with ESMTP for ; Wed, 20 May 2020 11:13:30 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 7017168BEB; Wed, 20 May 2020 13:13:25 +0200 (CEST) Date: Wed, 20 May 2020 13:13:24 +0200 From: Christoph Hellwig To: Masami Hiramatsu Cc: Christoph Hellwig , x86@kernel.org, Alexei Starovoitov , Daniel Borkmann , Linus Torvalds , Andrew Morton , linux-parisc@vger.kernel.org, linux-um@lists.infradead.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 13/20] maccess: always use strict semantics for probe_kernel_read Message-ID: <20200520111324.GA16488@lst.de> References: <20200519134449.1466624-1-hch@lst.de> <20200519134449.1466624-14-hch@lst.de> <20200520201126.f37d3b1e46355199216404e2@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200520201126.f37d3b1e46355199216404e2@kernel.org> User-Agent: Mutt/1.5.17 (2007-11-01) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000250, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, May 20, 2020 at 08:11:26PM +0900, Masami Hiramatsu wrote: > > - ret = probe_kernel_read(&c, (u8 *)addr + len, 1); > > + if (IS_ENABLED(CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE) && > > + (unsigned long)addr < TASK_SIZE) { > > + ret = probe_user_read(&c, > > + (__force u8 __user *)addr + len, 1); > > + } else { > > + ret = probe_kernel_read(&c, (u8 *)addr + len, 1); > > + } > > len++; > > } while (c && ret == 0 && len < MAX_STRING_SIZE); > > To avoid redundant check in the loop, we can use strnlen_user_nofault() out of > the loop. Something like below. Yes, I've done something very similar in response to Linus' comment (just using an ifdef instead).