Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751439AbdFZIGT (ORCPT ); Mon, 26 Jun 2017 04:06:19 -0400 Received: from mail-vk0-f54.google.com ([209.85.213.54]:35627 "EHLO mail-vk0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751353AbdFZIGQ (ORCPT ); Mon, 26 Jun 2017 04:06:16 -0400 MIME-Version: 1.0 In-Reply-To: References: <20170616174556.2358-1-fransklaver@gmail.com> <1497653077.10546.23.camel@perches.com> From: Frans Klaver Date: Mon, 26 Jun 2017 10:06:14 +0200 Message-ID: Subject: Re: endian bitshift defects [ was: staging: fusb302: don't bitshift __le16 type ] To: Julia Lawall Cc: Joe Perches , Greg Kroah-Hartman , kernel-janitors , Guenter Roeck , Yueyao Zhu , Rui Miguel Silva , Guru Das Srinagesh , Javier Martinez Canillas , devel@driverdev.osuosl.org, "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1559 Lines: 36 On Sat, Jun 24, 2017 at 1:37 AM, Julia Lawall wrote: > > > On Sat, 24 Jun 2017, Frans Klaver wrote: > >> Hm. For some reason the great mail filtering scheme decided to push >> this past my inbox :-/ >> >> On Sat, Jun 17, 2017 at 12:44 AM, Joe Perches wrote: >> > On Fri, 2017-06-16 at 19:45 +0200, Frans Klaver wrote: >> >> The header field in struct pd_message is declared as an __le16 type. The >> >> data in the message is supposed to be little endian. This means we don't >> >> have to go and shift the individual bytes into position when we're >> >> filling the buffer, we can just copy the contents right away. As an >> >> added benefit we don't get fishy results on big endian systems anymore. >> > >> > Thanks for pointing this out. >> > >> > There are several instances of this class of error. >> >> There are other smells around __(le|be) types that show up in staging >> that might be worth checking in the rest of the kernel as well. e.g. >> converting to cpu and storing it back into itself (possibly with its >> bytes reversed), direct assignments without conversion and what else >> you might have. sparse obviously already flags anything fishy going on >> with these types, but cannot distinguish between the classes of >> errors. I'll need to acquaint myself with spatch a bit more to be able >> to track that down. > > If you have concrete code examples, even fake ones, illustrating a class > of problem, then that would be great. I'll see if I can produce some somewhere this week. Thanks, Frans