From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755447AbaIDUOL (ORCPT ); Thu, 4 Sep 2014 16:14:11 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:55269 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755314AbaIDUOJ (ORCPT ); Thu, 4 Sep 2014 16:14:09 -0400 Date: Thu, 4 Sep 2014 13:14:08 -0700 From: Andrew Morton To: Scotty Bauer Cc: linux-kernel@vger.kernel.org, clemens@ladisch.de Subject: Re: [PATCH] kern/sys: Compat sysinfo syscall fix undefined behavior Message-Id: <20140904131408.5b50c44315263c497ac7d818@linux-foundation.org> In-Reply-To: <5408B39D.4030400@eng.utah.edu> References: <5408B39D.4030400@eng.utah.edu> X-Mailer: Sylpheed 3.2.0beta5 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 04 Sep 2014 12:46:53 -0600 Scotty Bauer wrote: > Fix undefined behavior and compiler warning by replacing right > shift 32 with upper_32_bits macro > > Signed-off-by: Scotty Bauer > --- > kernel/sys.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/sys.c b/kernel/sys.c > index ce81291..c78530b 100644 > --- a/kernel/sys.c > +++ b/kernel/sys.c > @@ -2135,7 +2135,7 @@ COMPAT_SYSCALL_DEFINE1(sysinfo, struct compat_sysinfo __user *, info) > /* Check to see if any memory value is too large for 32-bit and scale > * down if needed > */ > - if ((s.totalram >> 32) || (s.totalswap >> 32)) { > + if (upper_32_bits(s.totalram) || upper_32_bits(s.totalswap)) { > int bitcount = 0; > > while (s.mem_unit < PAGE_SIZE) { Fair enough. If I'm reading it correctly, this is all dead code because si_meminfo() unconditionally sets sysinfo.mem_unit to PAGE_SIZE. It could all do with a bit of a cleanup, I suspect.