From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]:34596 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726342AbgKBSXQ (ORCPT ); Mon, 2 Nov 2020 13:23:16 -0500 From: David Laight Subject: RE: Buggy commit tracked to: "Re: [PATCH 2/9] iov_iter: move rw_copy_check_uvector() into lib/iov_iter.c" Date: Mon, 2 Nov 2020 18:23:11 +0000 Message-ID: References: <20201022121849.GA1664412@kroah.com> <98d9df88-b7ef-fdfb-7d90-2fa7a9d7bab5@redhat.com> <20201022125759.GA1685526@kroah.com> <20201022135036.GA1787470@kroah.com> <134f162d711d466ebbd88906fae35b33@AcuMS.aculab.com> <935f7168-c2f5-dd14-7124-412b284693a2@redhat.com> <999e2926-9a75-72fd-007a-1de0af341292@redhat.com> <35d0ec90ef4f4a35a75b9df7d791f719@AcuMS.aculab.com> <20201023144718.GA2525489@kroah.com> <0ab5ac71f28d459db2f350c2e07b88ca@AcuMS.aculab.com> <20201102135202.GA1016272@kroah.com> In-Reply-To: <20201102135202.GA1016272@kroah.com> MIME-Version: 1.0 Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT List-ID: To: 'Greg KH' Cc: 'David Hildenbrand' , Al Viro , Nick Desaulniers , Christoph Hellwig , "kernel-team@android.com" , Andrew Morton , Jens Axboe , Arnd Bergmann , 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" From: 'Greg KH' > Sent: 02 November 2020 13:52 > > On Mon, Nov 02, 2020 at 09:06:38AM +0000, David Laight wrote: > > From: 'Greg KH' > > > Sent: 23 October 2020 15:47 > > > > > > On Fri, Oct 23, 2020 at 02:39:24PM +0000, David Laight wrote: > > > > From: David Hildenbrand > > > > > Sent: 23 October 2020 15:33 > > > > ... > > > > > I just checked against upstream code generated by clang 10 and it > > > > > properly discards the upper 32bit via a mov w23 w2. > > > > > > > > > > So at least clang 10 indeed properly assumes we could have garbage and > > > > > masks it off. > > > > > > > > > > Maybe the issue is somewhere else, unrelated to nr_pages ... or clang 11 > > > > > behaves differently. > > > > > > > > We'll need the disassembly from a failing kernel image. > > > > It isn't that big to hand annotate. > > > > > > I've worked around the merge at the moment in the android tree, but it > > > is still quite reproducable, and will try to get a .o file to > > > disassemble on Monday or so... > > > > Did this get properly resolved? > > For some reason, 5.10-rc2 fixed all of this up. I backed out all of the > patches I had to revert to get 5.10-rc1 to work properly, and then did > the merge and all is well. > > It must have been something to do with the compat changes in this same > area that went in after 5.10-rc1, and something got reorganized in the > files somehow. I really do not know, and at the moment, don't have the > time to track it down anymore. So for now, I'd say it's all good, sorry > for the noise. Hopefully it won't appear again. Saved me spending a day off reading arm64 assembler. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)