mac80211: fix remain-on-channel cancel crash

If a ROC item is canceled just as it expires, the work
struct may be scheduled while it is running (and waiting
for the mutex). This results in it being run after being
freed, which obviously crashes.

To fix this don't free it when aborting is requested but
instead mark it as "to be freed", which makes the work a
no-op and allows freeing it outside.

Cc: stable@vger.kernel.org [3.6+]
Reported-by: Jouni Malinen <j@w1.fi>
Tested-by: Jouni Malinen <j@w1.fi>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 388580a1bada..7bdefd901f9d 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -309,6 +309,7 @@ struct ieee80211_roc_work {
         struct ieee80211_channel *chan;
 
         bool started, abort, hw_begun, notified;
+        bool to_be_freed;
 
         unsigned long hw_start_time;
 
@@ -1347,7 +1348,7 @@ void ieee80211_offchannel_return(struct ieee80211_local *local);
 void ieee80211_roc_setup(struct ieee80211_local *local);
 void ieee80211_start_next_roc(struct ieee80211_local *local);
 void ieee80211_roc_purge(struct ieee80211_sub_if_data *sdata);
-void ieee80211_roc_notify_destroy(struct ieee80211_roc_work *roc);
+void ieee80211_roc_notify_destroy(struct ieee80211_roc_work *roc, bool free);
 void ieee80211_sw_roc_work(struct work_struct *work);
 void ieee80211_handle_roc_started(struct ieee80211_roc_work *roc);