From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:47693 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756149AbbGDDFm (ORCPT ); Fri, 3 Jul 2015 23:05:42 -0400 Subject: Patch "mac80211: fix locking in update_vlan_tailroom_need_count()" has been added to the 4.1-stable tree To: johannes.berg@intel.com, davem@davemloft.net, gregkh@linuxfoundation.org Cc: , From: Date: Fri, 03 Jul 2015 20:05:18 -0700 Message-ID: <143597911815728@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled mac80211: fix locking in update_vlan_tailroom_need_count() to the 4.1-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mac80211-fix-locking-in-update_vlan_tailroom_need_count.patch and it can be found in the queue-4.1 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From foo@baz Fri Jul 3 20:00:25 PDT 2015 From: Johannes Berg Date: Wed, 17 Jun 2015 13:54:54 +0200 Subject: mac80211: fix locking in update_vlan_tailroom_need_count() From: Johannes Berg [ Upstream commit 51f458d9612177f69c2e2c437034ae15f93078e7 ] Unfortunately, Michal's change to fix AP_VLAN crypto tailroom caused a locking issue that was reported by lockdep, but only in a few cases - the issue was a classic ABBA deadlock caused by taking the mtx after the key_mtx, where normally they're taken the other way around. As the key mutex protects the field in question (I'm adding a few annotations to make that clear) only the iteration needs to be protected, but we can also iterate the interface list with just RCU protection while holding the key mutex. Fixes: f9dca80b98ca ("mac80211: fix AP_VLAN crypto tailroom calculation") Signed-off-by: Johannes Berg Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/mac80211/key.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) --- a/net/mac80211/key.c +++ b/net/mac80211/key.c @@ -66,12 +66,15 @@ update_vlan_tailroom_need_count(struct i if (sdata->vif.type != NL80211_IFTYPE_AP) return; - mutex_lock(&sdata->local->mtx); + /* crypto_tx_tailroom_needed_cnt is protected by this */ + assert_key_lock(sdata->local); - list_for_each_entry(vlan, &sdata->u.ap.vlans, u.vlan.list) + rcu_read_lock(); + + list_for_each_entry_rcu(vlan, &sdata->u.ap.vlans, u.vlan.list) vlan->crypto_tx_tailroom_needed_cnt += delta; - mutex_unlock(&sdata->local->mtx); + rcu_read_unlock(); } static void increment_tailroom_need_count(struct ieee80211_sub_if_data *sdata) @@ -95,6 +98,8 @@ static void increment_tailroom_need_coun * http://mid.gmane.org/1308590980.4322.19.camel@jlt3.sipsolutions.net */ + assert_key_lock(sdata->local); + update_vlan_tailroom_need_count(sdata, 1); if (!sdata->crypto_tx_tailroom_needed_cnt++) { @@ -109,6 +114,8 @@ static void increment_tailroom_need_coun static void decrease_tailroom_need_count(struct ieee80211_sub_if_data *sdata, int delta) { + assert_key_lock(sdata->local); + WARN_ON_ONCE(sdata->crypto_tx_tailroom_needed_cnt < delta); update_vlan_tailroom_need_count(sdata, -delta); Patches currently in stable-queue which might be from johannes.berg@intel.com are queue-4.1/mac80211-fix-locking-in-update_vlan_tailroom_need_count.patch