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=-5.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 04170C43465 for ; Mon, 21 Sep 2020 15:12:45 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A691E2075E for ; Mon, 21 Sep 2020 15:12:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Cf0cwSkw" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A691E2075E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=SDQIkEnjs85LPB9GadpckmNp5IzDPjQJVF2Hk4zKw7M=; b=Cf0cwSkw+VckL88iqoW8PDU1R a5lfIZ4UMyB8Dye3+LNRrJTSbVhAqm0G8Le/yV9OaJ9Ca4GWmZ3kH/GHUTaggtOH2w745NWnujLnd fpwVzBhNLOs7XAsQvyIcOyadur+IGiJ45Wam5vS1185dJ7LrZ/cvkWaK7t23nR/jr/fP8/ZNQ8Evt +Aq0g4WIaTZfpIJiEWZpWQbfPrhsv0wx2dQOFOjRjL0ZsxUhRso7DGGplbeVNzyKS3Qg6FoHPet3d N/H4+m/KExQNyHGWUEuzDShhItY/pvXbdraAvJQRL10poaHuOq1OO+Lsd4A+z8Hsjqe42KPpDaGWZ RtZfkWGsw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kKNTS-000635-3Z; Mon, 21 Sep 2020 15:11:26 +0000 Received: from [2002:c35c:fd02::1] (helo=ZenIV.linux.org.uk) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kKNTO-000627-VE for linux-arm-kernel@lists.infradead.org; Mon, 21 Sep 2020 15:11:23 +0000 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kKNTL-003Byz-4d; Mon, 21 Sep 2020 15:11:19 +0000 Date: Mon, 21 Sep 2020 16:11:19 +0100 From: Al Viro To: David Laight Subject: Re: [PATCH 04/11] iov_iter: explicitly check for CHECK_IOVEC_ONLY in rw_copy_check_uvector Message-ID: <20200921151119.GU3421308@ZenIV.linux.org.uk> References: <20200921143434.707844-1-hch@lst.de> <20200921143434.707844-5-hch@lst.de> <7336624280b8444fb4cb00407317741b@AcuMS.aculab.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <7336624280b8444fb4cb00407317741b@AcuMS.aculab.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200921_111123_352031_2897AE0A X-CRM114-Status: GOOD ( 14.29 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "linux-aio@kvack.org" , "linux-mips@vger.kernel.org" , David Howells , "linux-mm@kvack.org" , "keyrings@vger.kernel.org" , "sparclinux@vger.kernel.org" , 'Christoph Hellwig' , "linux-arch@vger.kernel.org" , "linux-s390@vger.kernel.org" , "linux-scsi@vger.kernel.org" , Arnd Bergmann , "linux-block@vger.kernel.org" , "io-uring@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Jens Axboe , "linux-parisc@vger.kernel.org" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-security-module@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , Andrew Morton , "linuxppc-dev@lists.ozlabs.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Sep 21, 2020 at 03:05:32PM +0000, David Laight wrote: > I've actually no idea: > 1) Why there is an access_ok() check here. > It will be repeated by the user copy functions. Early sanity check. > 2) Why it isn't done when called from mm/process_vm_access.c. > Ok, the addresses refer to a different process, but they > must still be valid user addresses. > > Is 2 a legacy from when access_ok() actually checked that the > addresses were mapped into the process's address space? It never did. 2 is for the situation when a 32bit process accesses 64bit one; addresses that are perfectly legitimate for 64bit userland (and fitting into the first 4Gb of address space, so they can be represented by 32bit pointers just fine) might be rejected by access_ok() if the caller is 32bit. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel