From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932452Ab1CEBA4 (ORCPT ); Fri, 4 Mar 2011 20:00:56 -0500 Received: from kroah.org ([198.145.64.141]:50441 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760507Ab1CEBAu (ORCPT ); Fri, 4 Mar 2011 20:00:50 -0500 X-Mailbox-Line: From gregkh@clark.kroah.org Fri Mar 4 16:56:40 2011 Message-Id: <20110305005640.246381576@clark.kroah.org> User-Agent: quilt/0.48-11.2 Date: Fri, 04 Mar 2011 16:56:03 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Daniel J Blueman , Johannes Berg , "John W. Linville" Subject: [58/73] fix cfg80211_wext_siwfreq lock ordering... In-Reply-To: <20110305005720.GA16162@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.37-stable review patch. If anyone has any objections, please let us know. ------------------ From: Daniel J Blueman commit 4f919a3bc54da01db829c520ce4b1fabfde1c3f7 upstream. I previously managed to reproduce a hang while scanning wireless channels (reproducible with airodump-ng hopping channels); subsequent lockdep instrumentation revealed a lock ordering issue. Without knowing the design intent, it looks like the locks should be taken in reverse order; please comment. ======================================================= [ INFO: possible circular locking dependency detected ] 2.6.38-rc5-341cd #4 ------------------------------------------------------- airodump-ng/15445 is trying to acquire lock: (&rdev->devlist_mtx){+.+.+.}, at: [] cfg80211_wext_siwfreq+0xc6/0x100 but task is already holding lock: (&wdev->mtx){+.+.+.}, at: [] cfg80211_wext_siwfreq+0xbc/0x100 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&wdev->mtx){+.+.+.}: [] lock_acquire+0xc6/0x280 [] mutex_lock_nested+0x6e/0x4b0 [] cfg80211_netdev_notifier_call+0x430/0x5f0 [] notifier_call_chain+0x8b/0x100 [] raw_notifier_call_chain+0x11/0x20 [] call_netdevice_notifiers+0x32/0x60 [] __dev_notify_flags+0x34/0x80 [] dev_change_flags+0x40/0x70 [] do_setlink+0x1fc/0x8d0 [] rtnl_setlink+0xf2/0x140 [] rtnetlink_rcv_msg+0x163/0x270 [] netlink_rcv_skb+0xa1/0xd0 [] rtnetlink_rcv+0x20/0x30 [] netlink_unicast+0x2ba/0x300 [] netlink_sendmsg+0x267/0x3e0 [] sock_sendmsg+0xe4/0x110 [] sys_sendmsg+0x253/0x3b0 [] system_call_fastpath+0x16/0x1b -> #0 (&rdev->devlist_mtx){+.+.+.}: [] __lock_acquire+0x1622/0x1d10 [] lock_acquire+0xc6/0x280 [] mutex_lock_nested+0x6e/0x4b0 [] cfg80211_wext_siwfreq+0xc6/0x100 [] ioctl_standard_call+0x5d/0xd0 [] T.808+0x163/0x170 [] wext_handle_ioctl+0x3a/0x90 [] dev_ioctl+0x6f2/0x830 [] sock_ioctl+0xfd/0x290 [] do_vfs_ioctl+0x9d/0x590 [] sys_ioctl+0x4a/0x80 [] system_call_fastpath+0x16/0x1b other info that might help us debug this: 2 locks held by airodump-ng/15445: #0: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x12/0x20 #1: (&wdev->mtx){+.+.+.}, at: [] cfg80211_wext_siwfreq+0xbc/0x100 stack backtrace: Pid: 15445, comm: airodump-ng Not tainted 2.6.38-rc5-341cd #4 Call Trace: [] ? print_circular_bug+0xfa/0x100 [] ? __lock_acquire+0x1622/0x1d10 [] ? trace_hardirqs_off_caller+0x29/0xc0 [] ? lock_acquire+0xc6/0x280 [] ? cfg80211_wext_siwfreq+0xc6/0x100 [] ? mark_held_locks+0x67/0x90 [] ? mutex_lock_nested+0x6e/0x4b0 [] ? cfg80211_wext_siwfreq+0xc6/0x100 [] ? mark_held_locks+0x67/0x90 [] ? cfg80211_wext_siwfreq+0xc6/0x100 [] ? cfg80211_wext_siwfreq+0xc6/0x100 [] ? ioctl_standard_call+0x5d/0xd0 [] ? __dev_get_by_name+0x9b/0xc0 [] ? ioctl_standard_call+0x0/0xd0 [] ? T.808+0x163/0x170 [] ? might_fault+0x72/0xd0 [] ? wext_handle_ioctl+0x3a/0x90 [] ? might_fault+0xbb/0xd0 [] ? dev_ioctl+0x6f2/0x830 [] ? put_lock_stats+0xe/0x40 [] ? lock_release_holdtime+0xac/0x150 [] ? sock_ioctl+0xfd/0x290 [] ? do_vfs_ioctl+0x9d/0x590 [] ? fget_light+0x1df/0x3c0 [] ? sys_ioctl+0x4a/0x80 [] ? system_call_fastpath+0x16/0x1b Signed-off-by: Daniel J Blueman Acked-by: Johannes Berg Signed-off-by: John W. Linville Signed-off-by: Greg Kroah-Hartman --- net/wireless/wext-compat.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/net/wireless/wext-compat.c +++ b/net/wireless/wext-compat.c @@ -802,11 +802,11 @@ int cfg80211_wext_siwfreq(struct net_dev return freq; if (freq == 0) return -EINVAL; - wdev_lock(wdev); mutex_lock(&rdev->devlist_mtx); + wdev_lock(wdev); err = cfg80211_set_freq(rdev, wdev, freq, NL80211_CHAN_NO_HT); - mutex_unlock(&rdev->devlist_mtx); wdev_unlock(wdev); + mutex_unlock(&rdev->devlist_mtx); return err; default: return -EOPNOTSUPP;