commit 48027d7bc5ec0968ac4c4874bbea55701da25e2f
author Jan Grulich <grulja@gmail.com> Thu Aug 04 11:45:19 2022 +0200
committer WebRTC LUCI CQ <webrtc-scoped@luci-project-accounts.iam.gserviceaccount.com> Mon Aug 08 17:19:46 2022 +0000
tree 13ebe57d2d6ec3f03da6a830114ba9bdc9b82962
parent f449af8dd9e507ee2ff0af42a9a42506b2d38a29

Wayland screencast: fix crash on fd ownership violation

We pass the fd we recieve from xdg-desktop-portal to PipeWire to connect
to it and according to the specification PipeWire automatically closes
it on disconnect or failure. We also close the fd ourself when we tear
down the portal connection so we have to avoid doing this twice. Looks
OBS studio just duplicates the fd passed to PipeWire so do the same in
order to avoid the fd ownership violation once we stop sharing.

The fd we recieve from xdg-desktop-portal is from PipeWire also using
fcntl() with F_DUPFD_CLOEXEC option.

Bug: chromium:1339236
Change-Id: Ia7aee36e520dd5ff9a40688a6807e31c4e636f8e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/270421
Commit-Queue: Alexander Cooper <alcooper@chromium.org>
Reviewed-by: Alexander Cooper <alcooper@chromium.org>
Cr-Commit-Position: refs/heads/main@{#37712}

modules/desktop_capture/linux/wayland/shared_screencast_stream.cc

diff --git a/modules/desktop_capture/linux/wayland/shared_screencast_stream.cc b/modules/desktop_capture/linux/wayland/shared_screencast_stream.cc
index 3c4344f..5128091 100644
--- a/modules/desktop_capture/linux/wayland/shared_screencast_stream.cc
+++ b/modules/desktop_capture/linux/wayland/shared_screencast_stream.cc
@@ -10,6 +10,7 @@
 
 #include "modules/desktop_capture/linux/wayland/shared_screencast_stream.h"
 
+#include <fcntl.h>
 #include <libdrm/drm_fourcc.h>
 #include <pipewire/pipewire.h>
 #include <spa/param/video/format-utils.h>
@@ -97,7 +98,6 @@
 
  private:
   uint32_t pw_stream_node_id_ = 0;
-  int pw_fd_ = -1;
 
   DesktopSize stream_size_ = {};
   DesktopSize frame_size_;
@@ -408,7 +408,6 @@
   egl_dmabuf_ = std::make_unique<EglDmaBuf>();
 
   pw_stream_node_id_ = stream_node_id;
-  pw_fd_ = fd;
 
   pw_init(/*argc=*/nullptr, /*argc=*/nullptr);
 
@@ -442,10 +441,11 @@
   {
     PipeWireThreadLoopLock thread_loop_lock(pw_main_loop_);
 
-    if (!pw_fd_) {
-      pw_core_ = pw_context_connect(pw_context_, nullptr, 0);
+    if (fd >= 0) {
+      pw_core_ = pw_context_connect_fd(
+          pw_context_, fcntl(fd, F_DUPFD_CLOEXEC), nullptr, 0);
     } else {
-      pw_core_ = pw_context_connect_fd(pw_context_, pw_fd_, nullptr, 0);
+      pw_core_ = pw_context_connect(pw_context_, nullptr, 0);
     }
 
     if (!pw_core_) {
@@ -828,7 +828,7 @@
 }
 
 bool SharedScreenCastStream::StartScreenCastStream(uint32_t stream_node_id) {
-  return private_->StartScreenCastStream(stream_node_id, 0);
+  return private_->StartScreenCastStream(stream_node_id, -1);
 }
 
 bool SharedScreenCastStream::StartScreenCastStream(uint32_t stream_node_id,