From 666d707450eff6cc2946eba8edf67420f87ad11e Mon Sep 17 00:00:00 2001
From: Jan Grulich <grulja@gmail.com>
Date: Mon, 24 Jul 2023 15:29:11 +0200
Subject: [PATCH] Video capture PipeWire: guard callback to avoid concurrent
 access

Make sure the callback is reset when tearing down the PipeWireSession
and that there is no concurrent access to it, which can potentially lead
to a crash.

Bug: webrtc:15386
Change-Id: I0b09002fe0479dc1cd946c80684bcc5d8754d54a
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/311546
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Commit-Queue: Jan Grulich <grulja@gmail.com>
Cr-Commit-Position: refs/heads/main@{#40464}
---
 modules/video_capture/linux/pipewire_session.cc | 10 +++++++++-
 modules/video_capture/linux/pipewire_session.h  |  5 ++++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/modules/video_capture/linux/pipewire_session.cc b/modules/video_capture/linux/pipewire_session.cc
index 2adb1cdb50..3f52b3dd61 100644
--- a/modules/video_capture/linux/pipewire_session.cc
+++ b/modules/video_capture/linux/pipewire_session.cc
@@ -232,7 +232,10 @@ PipeWireSession::~PipeWireSession() {
 }
 
 void PipeWireSession::Init(VideoCaptureOptions::Callback* callback, int fd) {
-  callback_ = callback;
+  {
+    webrtc::MutexLock lock(&callback_lock_);
+    callback_ = callback;
+  }
 
   if (fd != kInvalidPipeWireFd) {
     InitPipeWire(fd);
@@ -374,6 +377,8 @@ void PipeWireSession::OnRegistryGlobalRemove(void* data, uint32_t id) {
 }
 
 void PipeWireSession::Finish(VideoCaptureOptions::Status status) {
+  webrtc::MutexLock lock(&callback_lock_);
+
   if (callback_) {
     callback_->OnInitialized(status);
     callback_ = nullptr;
@@ -381,6 +386,9 @@ void PipeWireSession::Finish(VideoCaptureOptions::Status status) {
 }
 
 void PipeWireSession::Cleanup() {
+  webrtc::MutexLock lock(&callback_lock_);
+  callback_ = nullptr;
+
   StopPipeWire();
 }
 
diff --git a/modules/video_capture/linux/pipewire_session.h b/modules/video_capture/linux/pipewire_session.h
index 982b468838..fdc06a6b2a 100644
--- a/modules/video_capture/linux/pipewire_session.h
+++ b/modules/video_capture/linux/pipewire_session.h
@@ -24,6 +24,7 @@
 #include "modules/video_capture/linux/camera_portal.h"
 #include "modules/video_capture/video_capture.h"
 #include "modules/video_capture/video_capture_options.h"
+#include "rtc_base/synchronization/mutex.h"
 
 namespace webrtc {
 namespace videocapturemodule {
@@ -117,7 +118,9 @@ class PipeWireSession : public rtc::RefCountedNonVirtual<PipeWireSession> {
   void Finish(VideoCaptureOptions::Status status);
   void Cleanup();
 
-  VideoCaptureOptions::Callback* callback_ = nullptr;
+  webrtc::Mutex callback_lock_;
+  VideoCaptureOptions::Callback* callback_ RTC_GUARDED_BY(&callback_lock_) =
+      nullptr;
 
   VideoCaptureOptions::Status status_;