cfg80211: fix deadlock with rfkill/sched_scan by adding new mutex
There was a deadlock when rfkill-blocking a wireless interface,
because we were locking the rdev mutex on NETDEV_GOING_DOWN to stop
sched_scans that were eventually running. The rfkill block code was
already holding a mutex under rdev:
kernel: =======================================================
kernel: [ INFO: possible circular locking dependency detected ]
kernel: 3.0.0-rc1-00049-g1fa7b6a #57
kernel: -------------------------------------------------------
kernel: kworker/0:1/4525 is trying to acquire lock:
kernel: (&rdev->mtx){+.+.+.}, at: [<ffffffff8164c831>] cfg80211_netdev_notifier_call+0x131/0x5b0
kernel:
kernel: but task is already holding lock:
kernel: (&rdev->devlist_mtx){+.+.+.}, at: [<ffffffff8164dcef>] cfg80211_rfkill_set_block+0x4f/0xa0
kernel:
kernel: which lock already depends on the new lock.
To fix this, add a new mutex specifically for sched_scan, to protect
the sched_scan_req element in the rdev struct, instead of using the
global rdev mutex.
Reported-by: Duane Griffin <duaneg@dghda.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/wireless/core.c b/net/wireless/core.c
index c22ef34..880dbe2 100644
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -366,6 +366,7 @@
mutex_init(&rdev->mtx);
mutex_init(&rdev->devlist_mtx);
+ mutex_init(&rdev->sched_scan_mtx);
INIT_LIST_HEAD(&rdev->netdev_list);
spin_lock_init(&rdev->bss_lock);
INIT_LIST_HEAD(&rdev->bss_list);
@@ -701,6 +702,7 @@
rfkill_destroy(rdev->rfkill);
mutex_destroy(&rdev->mtx);
mutex_destroy(&rdev->devlist_mtx);
+ mutex_destroy(&rdev->sched_scan_mtx);
list_for_each_entry_safe(scan, tmp, &rdev->bss_list, list)
cfg80211_put_bss(&scan->pub);
cfg80211_rdev_free_wowlan(rdev);
@@ -737,12 +739,16 @@
___cfg80211_scan_done(rdev, true);
}
+ cfg80211_unlock_rdev(rdev);
+
+ mutex_lock(&rdev->sched_scan_mtx);
+
if (WARN_ON(rdev->sched_scan_req &&
rdev->sched_scan_req->dev == wdev->netdev)) {
__cfg80211_stop_sched_scan(rdev, false);
}
- cfg80211_unlock_rdev(rdev);
+ mutex_unlock(&rdev->sched_scan_mtx);
mutex_lock(&rdev->devlist_mtx);
rdev->opencount--;
@@ -830,9 +836,9 @@
break;
case NL80211_IFTYPE_P2P_CLIENT:
case NL80211_IFTYPE_STATION:
- cfg80211_lock_rdev(rdev);
+ mutex_lock(&rdev->sched_scan_mtx);
__cfg80211_stop_sched_scan(rdev, false);
- cfg80211_unlock_rdev(rdev);
+ mutex_unlock(&rdev->sched_scan_mtx);
wdev_lock(wdev);
#ifdef CONFIG_CFG80211_WEXT