Return-path: Received: from mail-ig0-f181.google.com ([209.85.213.181]:50171 "EHLO mail-ig0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759833AbaEMJJt (ORCPT ); Tue, 13 May 2014 05:09:49 -0400 Received: by mail-ig0-f181.google.com with SMTP id h3so132206igd.8 for ; Tue, 13 May 2014 02:09:49 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20140513090056.GA31546@qca.qualcomm.com> References: <1399447378-31503-1-git-send-email-dh.herrmann@gmail.com> <20140507195435.GF20432@tuxdriver.com> <536A9479.8010201@openwrt.org> <20140512174910.GM17022@tuxdriver.com> <53711646.1030909@openwrt.org> <20140513090056.GA31546@qca.qualcomm.com> Date: Tue, 13 May 2014 11:09:48 +0200 Message-ID: (sfid-20140513_110957_930539_187BA736) Subject: Re: [ath9k-devel] [PATCH] ath9k: fix NULL-deref in hw_per_calibration() for ar9002 From: David Herrmann To: Rajkumar Manoharan Cc: Felix Fietkau , "John W. Linville" , Vasanthakumar Thiagarajan , ath9k-devel@venema.h4ckr.net, linux-wireless , Jouni Malinen , "Luis R. Rodriguez" , Senthil Balasubramanian Content-Type: text/plain; charset=UTF-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: Hi On Tue, May 13, 2014 at 11:00 AM, Rajkumar Manoharan wrote: > On Tue, May 13, 2014 at 08:50:00AM +0200, David Herrmann wrote: >> Hi >> >> On Mon, May 12, 2014 at 8:43 PM, Felix Fietkau wrote: >> > I looked into it again, the scenario where I assumed that this problem >> > could occur didn't turn out to be true. I have no idea how this crash >> > can occur. >> >> The only path that can set ah->caldata to NULL is through: >> >> ieee80211_hw_config() >> ath9k_htc_config() >> ath9k_htc_set_channel() >> ath9k_hw_reset() >> >> This happens whenever IEEE80211_CONF_OFFCHANNEL is set. >> >> Now mac80211 is way to big for me to review right now and >> ieee80211_hw_config() is used quite often. Given that the described >> call-path does no synchronization against ath9k_htc_ani_work(), all >> the callers of mac80211_hw_config(OFFCHANNEL) must guarantee that no >> ani-work is running. Is that intentional? I cannot see any of those >> functions calling into ath9k_htc_stop_ani(). This might of course be >> implicit. >> >> One call-path I see is: >> ieee80211_scan_cancel() >> cancel_delayed_work() >> >> We cannot use cancel_delayed_work_sync() here due to locking issues. >> However, this obviously races against any following >> set_channel(OFFCHANNEL) request. >> >> If there's anything I can do to debug this, let me know. I tried >> adding some printk()'s into the hot-path and it turns out to no longer >> fail then. So this really seems to be a quite small race (given that a >> bunch of simple printk()s is slow enough to work around it). > > David, > > Are you using USB devices? What is the PID/VID? I have not looked at > HTC driver perspective. Yes, I'm using the htc driver. I thought that was clear by pointing at ar9002, but I was wrong, sorry. lsusb information is: 'Bus 003 Device 056: ID 0411:017f BUFFALO INC. (formerly MelCo., Inc.) Sony UWA-BR100 802.11abgn Wireless Adapter [Atheros AR7010+AR9280]' Thanks David