[ 35/64] mac80211: fix remain-on-channel cancel crash

[Greg Kroah-Hartman]

3.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johannes Berg <johannes.berg@xxxxxxxxx>

commit 3fbd45ca8d1c98f3c2582ef8bc70ade42f70947b upstream.

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.

Reported-by: Jouni Malinen <j@xxxxx>
Tested-by: Jouni Malinen <j@xxxxx>
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 net/mac80211/cfg.c         |    6 ++++--
 net/mac80211/ieee80211_i.h |    3 ++-
 net/mac80211/offchannel.c  |   23 +++++++++++++++++------
 3 files changed, 23 insertions(+), 9 deletions(-)

--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -2499,7 +2499,7 @@ static int ieee80211_cancel_roc(struct i
 			list_del(&dep->list);
 			mutex_unlock(&local->mtx);
 
-			ieee80211_roc_notify_destroy(dep);
+			ieee80211_roc_notify_destroy(dep, true);
 			return 0;
 		}
 
@@ -2539,7 +2539,7 @@ static int ieee80211_cancel_roc(struct i
 			ieee80211_start_next_roc(local);
 		mutex_unlock(&local->mtx);
 
-		ieee80211_roc_notify_destroy(found);
+		ieee80211_roc_notify_destroy(found, true);
 	} else {
 		/* work may be pending so use it all the time */
 		found->abort = true;
@@ -2549,6 +2549,8 @@ static int ieee80211_cancel_roc(struct i
 
 		/* work will clean up etc */
 		flush_delayed_work(&found->work);
+		WARN_ON(!found->to_be_freed);
+		kfree(found);
 	}
 
 	return 0;
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -346,6 +346,7 @@ struct ieee80211_roc_work {
 	struct ieee80211_channel *chan;
 
 	bool started, abort, hw_begun, notified;
+	bool to_be_freed;
 
 	unsigned long hw_start_time;
 
@@ -1363,7 +1364,7 @@ void ieee80211_offchannel_return(struct
 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);
 
--- a/net/mac80211/offchannel.c
+++ b/net/mac80211/offchannel.c
@@ -299,10 +299,13 @@ void ieee80211_start_next_roc(struct iee
 	}
 }
 
-void ieee80211_roc_notify_destroy(struct ieee80211_roc_work *roc)
+void ieee80211_roc_notify_destroy(struct ieee80211_roc_work *roc, bool free)
 {
 	struct ieee80211_roc_work *dep, *tmp;
 
+	if (WARN_ON(roc->to_be_freed))
+		return;
+
 	/* was never transmitted */
 	if (roc->frame) {
 		cfg80211_mgmt_tx_status(&roc->sdata->wdev,
@@ -318,9 +321,12 @@ void ieee80211_roc_notify_destroy(struct
 						   GFP_KERNEL);
 
 	list_for_each_entry_safe(dep, tmp, &roc->dependents, list)
-		ieee80211_roc_notify_destroy(dep);
+		ieee80211_roc_notify_destroy(dep, true);
 
-	kfree(roc);
+	if (free)
+		kfree(roc);
+	else
+		roc->to_be_freed = true;
 }
 
 void ieee80211_sw_roc_work(struct work_struct *work)
@@ -333,6 +339,9 @@ void ieee80211_sw_roc_work(struct work_s
 
 	mutex_lock(&local->mtx);
 
+	if (roc->to_be_freed)
+		goto out_unlock;
+
 	if (roc->abort)
 		goto finish;
 
@@ -372,7 +381,7 @@ void ieee80211_sw_roc_work(struct work_s
  finish:
 		list_del(&roc->list);
 		started = roc->started;
-		ieee80211_roc_notify_destroy(roc);
+		ieee80211_roc_notify_destroy(roc, !roc->abort);
 
 		if (started) {
 			drv_flush(local, false);
@@ -412,7 +421,7 @@ static void ieee80211_hw_roc_done(struct
 
 	list_del(&roc->list);
 
-	ieee80211_roc_notify_destroy(roc);
+	ieee80211_roc_notify_destroy(roc, true);
 
 	/* if there's another roc, start it now */
 	ieee80211_start_next_roc(local);
@@ -462,12 +471,14 @@ void ieee80211_roc_purge(struct ieee8021
 	list_for_each_entry_safe(roc, tmp, &tmp_list, list) {
 		if (local->ops->remain_on_channel) {
 			list_del(&roc->list);
-			ieee80211_roc_notify_destroy(roc);
+			ieee80211_roc_notify_destroy(roc, true);
 		} else {
 			ieee80211_queue_delayed_work(&local->hw, &roc->work, 0);
 
 			/* work will clean up etc */
 			flush_delayed_work(&roc->work);
+			WARN_ON(!roc->to_be_freed);
+			kfree(roc);
 		}
 	}
 


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