From a4888fcf8fada3aecfac42cfe2668514ea875c85 Mon Sep 17 00:00:00 2001
From: Raja Subramanian <raja.gobi@tutanota.com>
Date: Thu, 21 Dec 2023 16:02:10 +0530
Subject: [PATCH] Prevent unsafe access (hopefully). (#2332)

* Prevent unsafe access (hopefully).

Thank you @paulwe for catching it.

* prevent recursive locks
---
 pkg/rtc/mediatrackreceiver.go | 54 +++++++++++++++--------------------
 1 file changed, 23 insertions(+), 31 deletions(-)

diff --git a/pkg/rtc/mediatrackreceiver.go b/pkg/rtc/mediatrackreceiver.go
index b5fefa8a3..d04db1a02 100644
--- a/pkg/rtc/mediatrackreceiver.go
+++ b/pkg/rtc/mediatrackreceiver.go
@@ -133,13 +133,11 @@ func NewMediaTrackReceiver(params MediaTrackReceiverParams, ti *livekit.TrackInf
 }
 
 func (t *MediaTrackReceiver) Restart() {
-	t.lock.Lock()
-	receivers := t.receivers
-	ti := t.trackInfo
-	t.lock.Unlock()
+	t.lock.RLock()
+	hq := buffer.VideoQualityToSpatialLayer(livekit.VideoQuality_HIGH, t.trackInfo)
+	t.lock.RUnlock()
 
-	hq := buffer.VideoQualityToSpatialLayer(livekit.VideoQuality_HIGH, ti)
-	for _, receiver := range receivers {
+	for _, receiver := range t.Receivers() {
 		receiver.SetMaxExpectedSpatialLayer(hq)
 	}
 }
@@ -263,7 +261,6 @@ func (t *MediaTrackReceiver) ClearReceiver(mime string, willBeResumed bool) {
 			break
 		}
 	}
-
 	t.lock.Unlock()
 
 	t.removeAllSubscribersForMime(mime, willBeResumed)
@@ -271,14 +268,12 @@ func (t *MediaTrackReceiver) ClearReceiver(mime string, willBeResumed bool) {
 
 func (t *MediaTrackReceiver) ClearAllReceivers(willBeResumed bool) {
 	t.params.Logger.Debugw("clearing all receivers")
-	t.lock.Lock()
+	t.lock.RLock()
 	var mimes []string
 	for _, receiver := range t.receivers {
 		mimes = append(mimes, receiver.Codec().MimeType)
 	}
-
-	t.receivers = nil
-	t.lock.Unlock()
+	t.lock.RUnlock()
 
 	for _, mime := range mimes {
 		t.ClearReceiver(mime, willBeResumed)
@@ -418,9 +413,9 @@ func (t *MediaTrackReceiver) IsMuted() bool {
 func (t *MediaTrackReceiver) SetMuted(muted bool) {
 	t.lock.Lock()
 	t.trackInfo.Muted = muted
-	receivers := t.receivers
 	t.lock.Unlock()
-	for _, receiver := range receivers {
+
+	for _, receiver := range t.Receivers() {
 		receiver.SetUpTrackPaused(muted)
 	}
 
@@ -445,7 +440,7 @@ func (t *MediaTrackReceiver) AddSubscriber(sub types.LocalParticipant) (types.Su
 		return nil, ErrNotOpen
 	}
 
-	receivers := t.receivers
+	receivers := t.simulcastReceiversLocked()
 	potentialCodecs := make([]webrtc.RTPCodecParameters, len(t.potentialCodecs))
 	copy(potentialCodecs, t.potentialCodecs)
 	t.lock.RUnlock()
@@ -529,11 +524,10 @@ func (t *MediaTrackReceiver) RevokeDisallowedSubscribers(allowedSubscriberIdenti
 
 func (t *MediaTrackReceiver) updateTrackInfoOfReceivers() {
 	t.lock.RLock()
-	receivers := t.receivers
-	ti := t.trackInfo
+	ti := proto.Clone(t.trackInfo).(*livekit.TrackInfo)
 	t.lock.RUnlock()
 
-	for _, r := range receivers {
+	for _, r := range t.Receivers() {
 		r.UpdateTrackInfo(ti)
 	}
 }
@@ -821,10 +815,7 @@ func (t *MediaTrackReceiver) DebugInfo() map[string]interface{} {
 
 	info["DownTracks"] = t.MediaTrackSubscriptions.DebugInfo()
 
-	t.lock.RLock()
-	receivers := t.receivers
-	t.lock.RUnlock()
-	for _, receiver := range receivers {
+	for _, receiver := range t.Receivers() {
 		info[receiver.Codec().MimeType] = receiver.DebugInfo()
 	}
 
@@ -870,13 +861,17 @@ func (t *MediaTrackReceiver) Receivers() []sfu.TrackReceiver {
 	return receivers
 }
 
-func (t *MediaTrackReceiver) SetRTT(rtt uint32) {
-	t.lock.RLock()
-	receivers := t.receivers
-	t.lock.RUnlock()
+func (t *MediaTrackReceiver) simulcastReceiversLocked() []*simulcastReceiver {
+	receivers := make([]*simulcastReceiver, 0, len(t.receivers))
+	for _, r := range t.receivers {
+		receivers = append(receivers, r)
+	}
+	return receivers
+}
 
-	for _, r := range receivers {
-		if wr, ok := r.TrackReceiver.(*sfu.WebRTCReceiver); ok {
+func (t *MediaTrackReceiver) SetRTT(rtt uint32) {
+	for _, r := range t.Receivers() {
+		if wr, ok := r.(*sfu.WebRTCReceiver); ok {
 			wr.SetRTT(rtt)
 		}
 	}
@@ -906,10 +901,7 @@ func (t *MediaTrackReceiver) IsEncrypted() bool {
 }
 
 func (t *MediaTrackReceiver) GetTrackStats() *livekit.RTPStats {
-	t.lock.RLock()
-	receivers := t.receivers
-	t.lock.RUnlock()
-
+	receivers := t.Receivers()
 	stats := make([]*livekit.RTPStats, 0, len(receivers))
 	for _, receiver := range receivers {
 		receiverStats := receiver.GetTrackStats()