Return-path: Received: from bues.ch ([80.190.117.144]:56748 "EHLO bues.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751554Ab1H0VbU convert rfc822-to-8bit (ORCPT ); Sat, 27 Aug 2011 17:31:20 -0400 Date: Sat, 27 Aug 2011 23:31:11 +0200 From: Michael =?UTF-8?B?QsO8c2No?= To: Larry Finger Cc: wireless Subject: Re: [PATCH] b43: Fix smatch warning Message-ID: <20110827233111.6480df17@milhouse> (sfid-20110827_233126_188746_74F19B38) In-Reply-To: <4E59426F.1050401@lwfinger.net> References: <1314469560-28255-1-git-send-email-Larry.Finger@lwfinger.net> <20110827205404.62de7b31@milhouse> <4E59426F.1050401@lwfinger.net> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Sat, 27 Aug 2011 14:15:59 -0500 Larry Finger wrote: > On 08/27/2011 01:54 PM, Michael Büsch wrote: > > On Sat, 27 Aug 2011 13:26:00 -0500 > > Larry Finger wrote: > > > >> CHECK drivers/net/wireless/b43/main.c > >> drivers/net/wireless/b43/main.c +4115 b43_wireless_core_stop(7) warn: variable dereferenced before check 'dev' > > > >> This is next material. > > > > -next, just because the bug is not in the current kernel? > > Or because you think this is harmless? > > > > I'm not sure whether this is harmless. It effectively is that kind > > of bug that triggers dangerous compiler optimizations. > > I think the compiler has some freedom to assume dev can not be NULL when > > the function is entered and thus optimize out the !dev check. > > No, the check has to be left in due to the changing of dev in the routine > followed by a 'goto redo'. I think the compiler is still free to emit the !dev check twice. Or the other way around: Emit it correctly for the "goto" case and don't emit it for the function-enter case (and directly check dev->status). > In fact, a bug in the original code is unlikely, but my patch did add one. I > think the code should be > > if (!dev) > return NULL; > wl = dev->wl; > redo: yes -- Greetings, Michael.