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=-3.8 required=3.0 tests=BAYES_00, 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 1076AC388F7 for ; Thu, 22 Oct 2020 20:06:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 91F282462E for ; Thu, 22 Oct 2020 20:06:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S370874AbgJVUGo (ORCPT ); Thu, 22 Oct 2020 16:06:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57484 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S370843AbgJVUGn (ORCPT ); Thu, 22 Oct 2020 16:06:43 -0400 Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [IPv6:2002:c35c:fd02::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4F9B1C0613CE; Thu, 22 Oct 2020 13:06:43 -0700 (PDT) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kVgqz-006SmZ-1W; Thu, 22 Oct 2020 20:06:29 +0000 Date: Thu, 22 Oct 2020 21:06:29 +0100 From: Al Viro To: Nick Desaulniers Cc: Arnd Bergmann , David Laight , Christoph Hellwig , David Hildenbrand , Greg KH , "kernel-team@android.com" , Andrew Morton , Jens Axboe , David Howells , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-mips@vger.kernel.org" , "linux-parisc@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-s390@vger.kernel.org" , "sparclinux@vger.kernel.org" , "linux-block@vger.kernel.org" , "linux-scsi@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-aio@kvack.org" , "io-uring@vger.kernel.org" , "linux-arch@vger.kernel.org" , "linux-mm@kvack.org" , "netdev@vger.kernel.org" , "keyrings@vger.kernel.org" , "linux-security-module@vger.kernel.org" Subject: Re: Buggy commit tracked to: "Re: [PATCH 2/9] iov_iter: move rw_copy_check_uvector() into lib/iov_iter.c" Message-ID: <20201022200629.GX3576660@ZenIV.linux.org.uk> References: <5fd6003b-55a6-2c3c-9a28-8fd3a575ca78@redhat.com> <20201022132342.GB8781@lst.de> <8f1fff0c358b4b669d51cc80098dbba1@AcuMS.aculab.com> <20201022192458.GV3576660@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201022192458.GV3576660@ZenIV.linux.org.uk> Sender: Al Viro Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Thu, Oct 22, 2020 at 08:24:58PM +0100, Al Viro wrote: > Depending upon the calling conventions, compiler might do truncation in caller or > in a callee, but it must be done _somewhere_. Unless I'm misreading AAPCS64, "Unlike in the 32-bit AAPCS, named integral values must be narrowed by the callee rather than the caller" in 6.4.2 means that callee must not _not_ expect the upper 32 bits of %x0..%x7 to contain anything valid for 32bit arguments and it must zero-extend %w0..%w7 when passing that to something that expects a 64bit argument. On inlining it should be the same situation as storing unsigned int argument into unsigned long local variable and working with that - if void f(unsigned int w) { unsigned long x = w; printf("%lx\n", x); } ends up passing %x0 to printf, it's an obvious bug - it must do something like uxtw x0, w0 first. What am I missing here?