From 0ff6ce7b36199f67f709c750e9a2a66659a4babe Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Mon, 17 Aug 2009 12:25:37 +0200 Subject: [PATCH 1/1] cfg80211: fix deadlock When removing an interface with nl80211, cfg80211 will deadlock in the netdev notifier because we're already holding rdev->mtx and try to acquire it again to verify the scan has been done. This bug was introduced by my patch "cfg80211: check for and abort dangling scan requests". To fix this, move the dangling scan request check into wiphy_unregister(). This will not be able to catch all cases right away, but if the scan problem happens with a manual ifdown or so it will be possible to remedy it by removing the module/device. Additionally, add comments about the deadlock scenario. Reported-by: Christian Lamparter Signed-off-by: Johannes Berg Tested-by: Christian Lamparter Tested-by: Kalle Valo Signed-off-by: John W. Linville --- net/wireless/core.c | 30 ++++++++++++++++++------------ 1 file changed, 18 insertions(+), 12 deletions(-) diff --git a/net/wireless/core.c b/net/wireless/core.c index bc99e4ec7463..69a185ba9ff1 100644 --- a/net/wireless/core.c +++ b/net/wireless/core.c @@ -586,9 +586,14 @@ void wiphy_unregister(struct wiphy *wiphy) * get to lock contention here if userspace issues a command * that identified the hardware by wiphy index. */ - mutex_lock(&rdev->mtx); - /* unlock again before freeing */ - mutex_unlock(&rdev->mtx); + cfg80211_lock_rdev(rdev); + + if (WARN_ON(rdev->scan_req)) { + rdev->scan_req->aborted = true; + ___cfg80211_scan_done(rdev); + } + + cfg80211_unlock_rdev(rdev); cfg80211_debugfs_rdev_del(rdev); @@ -605,7 +610,6 @@ void wiphy_unregister(struct wiphy *wiphy) flush_work(&rdev->scan_done_wk); cancel_work_sync(&rdev->conn_work); - kfree(rdev->scan_req); flush_work(&rdev->event_work); } EXPORT_SYMBOL(wiphy_unregister); @@ -653,6 +657,11 @@ static int cfg80211_netdev_notifier_call(struct notifier_block * nb, switch (state) { case NETDEV_REGISTER: + /* + * NB: cannot take rdev->mtx here because this may be + * called within code protected by it when interfaces + * are added with nl80211. + */ mutex_init(&wdev->mtx); INIT_LIST_HEAD(&wdev->event_list); spin_lock_init(&wdev->event_lock); @@ -730,13 +739,11 @@ static int cfg80211_netdev_notifier_call(struct notifier_block * nb, #endif break; case NETDEV_UNREGISTER: - cfg80211_lock_rdev(rdev); - - if (WARN_ON(rdev->scan_req && rdev->scan_req->dev == dev)) { - rdev->scan_req->aborted = true; - ___cfg80211_scan_done(rdev); - } - + /* + * NB: cannot take rdev->mtx here because this may be + * called within code protected by it when interfaces + * are removed with nl80211. + */ mutex_lock(&rdev->devlist_mtx); /* * It is possible to get NETDEV_UNREGISTER @@ -755,7 +762,6 @@ static int cfg80211_netdev_notifier_call(struct notifier_block * nb, #endif } mutex_unlock(&rdev->devlist_mtx); - cfg80211_unlock_rdev(rdev); break; case NETDEV_PRE_UP: if (!(wdev->wiphy->interface_modes & BIT(wdev->iftype))) -- 2.30.2