From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]:36084 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754710AbdDDSxp (ORCPT ); Tue, 4 Apr 2017 14:53:45 -0400 Subject: Re: [PATCH] staging: Add rtl8723bs sdio wifi driver To: Larry Finger References: <20170329174751.13184-1-hdegoede@redhat.com> <4d1d3c02-eff6-0410-cee0-9360ec645e13@lwfinger.net> Cc: Bastien Nocera , Jes Sorensen , linux-wireless@vger.kernel.org From: Hans de Goede Message-ID: (sfid-20170404_205351_427988_EAF09808) Date: Tue, 4 Apr 2017 20:53:41 +0200 MIME-Version: 1.0 In-Reply-To: <4d1d3c02-eff6-0410-cee0-9360ec645e13@lwfinger.net> Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: Hi, On 04/04/2017 08:31 PM, Larry Finger wrote: > On 03/29/2017 12:47 PM, Hans de Goede wrote: >> The rtl8723bs is found on quite a few systems used by Linux users, >> such as on Atom systems (Intel Computestick and various other >> Atom based devices) and on many (budget) ARM boards such as >> the CHIP. >> >> The plan moving forward with this is for the new clean, >> written from scratch, rtl8xxxu driver to eventually gain >> support for sdio devices. But there is no clear timeline >> for that, so lets add this driver included in staging for now. > > Hans, > > I started looking at the Smatch errors. This one may be the result of a serious problem: > > CHECK drivers/staging/rtl8723bs/core/rtw_debug.c > drivers/staging/rtl8723bs/core/rtw_debug.c:454 proc_get_survey_info() error: we previously assumed 'phead' could be null (see line 453) > drivers/staging/rtl8723bs/core/rtw_debug.c:455 proc_get_survey_info() warn: variable dereferenced before check 'phead' (see line 454) > > A snippet of the code in question is as follows: > > spin_lock_bh(&(pmlmepriv->scanned_queue.lock)); > phead = get_list_head(queue); > plist = phead ? get_next(phead) : NULL; > plist = get_next(phead); > if ((!phead) || (!plist)) { > spin_unlock_bh(&(pmlmepriv->scanned_queue.lock)); > return 0; > } > > This code comes directly from the hadess repo, but I am suspicious of the double call to get_next(phead). I cannot imagine any valid reason to skip every other entry on that list. If you look closer and simplify the first getnext line what is written is: plist = get_next(phead); plist = get_next(phead); Which indeed looks like it could use improvement, but I don't think it is seriously broken. Regards, Hans