Return-path: Received: from gosford.compton.nu ([217.169.17.27]:42968 "EHLO gosford.compton.nu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753320AbbF2JUO (ORCPT ); Mon, 29 Jun 2015 05:20:14 -0400 Subject: Re: Null pointer dereference when station associates [introduced by 4.0.5?] To: Johannes Berg , linux-wireless@vger.kernel.org References: <558EC27A.60804@compton.nu> (sfid-20150627_181129_907073_7F8F41EE) <1435565678.2156.9.camel@sipsolutions.net> <55910222.8020906@compton.nu> Cc: stable@vger.kernel.org From: Tom Hughes Message-ID: <55910DC8.9040700@compton.nu> (sfid-20150629_112019_079235_734AF1AE) Date: Mon, 29 Jun 2015 10:20:08 +0100 MIME-Version: 1.0 In-Reply-To: <55910222.8020906@compton.nu> Content-Type: text/plain; charset=windows-1252 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 29/06/15 09:30, Tom Hughes wrote: > On 29/06/15 09:14, Johannes Berg wrote: >> On Sat, 2015-06-27 at 16:34 +0100, Tom Hughes wrote: >>> >>> Interestingly from what I can see this is trying to create a file >>> for the station at a path something like: >>> >>> ieee80211/phy0/netdev:XXXX/stations/XXXXXX >> >> indeed. >> >>> but in my (currently working) boot under 4.0.4 there is no netdev >>> directory under phy0 in debugfs... but then maybe that is the problem >>> as well if the inode pointer was null? >>> >> >> This is pretty strange - if the dentry pointer (sdata >> ->debugfs.subdir_stations) was NULL or an ERR_PTR(), the code would >> return pretty much immediately. >> >> So it looks like that pointer is valid, but it's ->d_inode was NULL? >> >> I'm not really sure how that could happen. > > Indeed I'm a bit puzzled... It looks like hostapd has something to do with it... If I stop hostapd and remove ath9k and then reprobe it then the netdev dir appears: gosford [~] % sudo modprobe ath9k gosford [~] % sudo ls /sys/kernel/debug/ieee80211/phy1 ath9k long_retry_limit reset user_power fragmentation_threshold netdev:wlp2s0 rts_threshold wep_iv ht40allow_map power short_retry_limit hwflags queues statistics keys rc total_ps_buffered Then I start hostapd and it vanishes: gosford [~] % sudo systemctl start hostapd gosford [~] % sudo ls /sys/kernel/debug/ieee80211/phy1 ath9k keys rc statistics fragmentation_threshold long_retry_limit reset total_ps_buffered ht40allow_map power rts_threshold user_power hwflags queues short_retry_limit wep_iv Tom -- Tom Hughes (tom@compton.nu) http://compton.nu/