From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751426AbcFXOqQ (ORCPT ); Fri, 24 Jun 2016 10:46:16 -0400 Received: from mail-oi0-f65.google.com ([209.85.218.65]:35669 "EHLO mail-oi0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750988AbcFXOqO (ORCPT ); Fri, 24 Jun 2016 10:46:14 -0400 Subject: Re: [ldv-project] [net] rtl8188ee: a potential race condition To: Vaishali Thakkar , Pavel Andrianov References: <575A788C.5020509@ispras.ru> <576D40F1.9040009@oracle.com> Cc: Chaoming Li , Kalle Valo , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, ldv-project@linuxtesting.org From: Larry Finger Message-ID: <576D47B3.60808@lwfinger.net> Date: Fri, 24 Jun 2016 09:46:11 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0 MIME-Version: 1.0 In-Reply-To: <576D40F1.9040009@oracle.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/24/2016 09:17 AM, Vaishali Thakkar wrote: > > > On Friday 10 June 2016 01:51 PM, Pavel Andrianov wrote: >> Hi! >> >> There is a potential data race in drivers/net/wireless/realtek/rtlwifi/rtl8188ee/rtl8188ee.ko. >> >> In the function rtl88ee_gpio_radio_on_off_checking the flag ppsc->rfchange_inprogress is set with a spinlock protection. In the function rtl_ps_set_rf_state the flag is read also under a spinlock. But the function rtl88e_dm_watchdog read it without any locks. As a result rtl88e_dm_watchdog may execute the succeeding code while changing (with the flag rfchange_inprogress == true). I do not exactly determine the consequences, but likely they are not good if there exists such check. Could anybody more confident confirm this? >> >> The function rtl_ps_set_rf_state is always called with its parameter [protect_or_not == false]. Is this flag really necessary, if the value 'true' is never used? The function is also set the flag ppsc->rfchange_inprogress and may affect the rtl88e_dm_watchdog as in the previous case. > > I think the patch was sent sometime ago for removing the parameter. But I am not sure why it's not applied. > May be Larry can have better idea about this. > > Here, is link to the patch: http://linux-wireless.vger.kernel.narkive.com/mu4t9xxr/patch-3-4-rtlwifi-rtl8192cu-remove-unused-parameter The patch for rtl8192cu was applied as commit 4b9d8d67b44a on Jun 20 2011, but the unused parameter was reintroduced as part of an update of the power-save code with commit d3feae41a347 on Sep 22 2014. My recollection is that Realtek envisioned a driver that needed this parameter to be true. As none has yet been introduced, I will prepare a patch to remove it again. I am also testing a patch to remove the race condition in rtl8188ee. Larry