mac80211: clean up remain-on-channel on interface stop

When any interface goes down, it could be the one that we
were doing a remain-on-channel with. We therefore need to
cancel the remain-on-channel and flush the related work
structs so they don't run after the interface has been
removed or even destroyed.

It's also possible in this case that an off-channel SKB
was never transmitted, so free it if this is the case.
Note that this can also happen if the driver finishes
the off-channel period without ever starting it.

Cc: [email protected]
Reported-by: Nirav Shah <[email protected]>
Signed-off-by: Johannes Berg <[email protected]>
Signed-off-by: John W. Linville <[email protected]>

net/mac80211/iface.c

@@ -637,6 +637,18 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
 		ieee80211_configure_filter(local);
 		break;
 	default:
+		mutex_lock(&local->mtx);
+		if (local->hw_roc_dev == sdata->dev &&
+		    local->hw_roc_channel) {
+			/* ignore return value since this is racy */
+			drv_cancel_remain_on_channel(local);
+			ieee80211_queue_work(&local->hw, &local->hw_roc_done);
+		}
+		mutex_unlock(&local->mtx);
+
+		flush_work(&local->hw_roc_start);
+		flush_work(&local->hw_roc_done);
+
 		flush_work(&sdata->work);
 		/*
 		 * When we get here, the interface is marked down.

net/mac80211/offchannel.c

@@ -234,6 +234,22 @@ static void ieee80211_hw_roc_done(struct work_struct *work)
 		return;
 	}
 
+	/* was never transmitted */
+	if (local->hw_roc_skb) {
+		u64 cookie;
+
+		cookie = local->hw_roc_cookie ^ 2;
+
+		cfg80211_mgmt_tx_status(local->hw_roc_dev, cookie,
+					local->hw_roc_skb->data,
+					local->hw_roc_skb->len, false,
+					GFP_KERNEL);
+
+		kfree_skb(local->hw_roc_skb);
+		local->hw_roc_skb = NULL;
+		local->hw_roc_skb_for_status = NULL;
+	}
+
 	if (!local->hw_roc_for_tx)
 		cfg80211_remain_on_channel_expired(local->hw_roc_dev,
 						   local->hw_roc_cookie,