From dee7ef85122fe988bfc8059a3fa5305109bc6999 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Barnab=C3=A1s=20P=C5=91cze?= <pobrn@protonmail.com>
Date: Sat, 21 Jan 2023 05:07:16 +0100
Subject: [PATCH] libobs-opengl: Do not close X11 platform display on error

The platform display is not owned by libobs, it should not
be closed. Doing so results in heap use-after-frees when
Qt components try to use it while trying to show
a message box about the failure:

  info: Initializing OpenGL...
  error: Failed to initialize EGL: EGL_BAD_ACCESS
  error: Failed to create context!
  error: device_create (GL) failed
  error: Failed to initialize video.  Your GPU may not be supported, or your graphics drivers may need to be updated.
  =================================================================
  ==2320345==ERROR: AddressSanitizer: heap-use-after-free on address 0x621000018668 at pc 0x7fcb75e20d6e bp 0x7ffe88d0e910 sp 0x7ffe88d0e900
  READ of size 8 at 0x621000018668 thread T0
      0 0x7fcb75e20d6d in XInternAtom /.../libx11/src/IntAtom.c:175
      1 0x7fcb6bf5edfd in Kvantum::ThemeConfig::getCompositeSpec()
      2 0x7fcb6bf0eb19 in Kvantum::Style::setSurfaceFormat(QWidget*) const
      3 0x7fcb6bf11bae in Kvantum::Style::styleHint(QStyle::StyleHint, QStyleOption const*, QWidget const*, QStyleHintReturn*) const
      4 0x5585cbce70b8 in OBSIgnoreWheelProxyStyle::styleHint(QStyle::StyleHint, QStyleOption const*, QWidget const*, QStyleHintReturn*) const /.../obs-studio/UI/obs-proxy-style.cpp:88
      5 0x7fcb85826515  (/usr/lib/libQt6Widgets.so.6+0x226515)
      6 0x7fcb859dbf1d  (/usr/lib/libQt6Widgets.so.6+0x3dbf1d)
      7 0x7fcb859dc5f0 in QMessageBox::QMessageBox(...)
      8 0x7fcb859dc6b1  (/usr/lib/libQt6Widgets.so.6+0x3dc6b1)
      9 0x5585cbd2fb31 in OBSErrorBoxva /.../obs-studio/UI/qt-wrappers.cpp:48
      10 0x5585cbd2fd34 in OBSErrorBox(QWidget*, char const*, ...) /.../obs-studio/UI/qt-wrappers.cpp:55
      11 0x5585cbcc3f36 in run_program /.../obs-studio/UI/obs-app.cpp:2475
      12 0x5585cbcc52b4 in main /.../obs-studio/UI/obs-app.cpp:3358
      13 0x7fcb82e3c28f  (/usr/lib/libc.so.6+0x2328f)
      14 0x7fcb82e3c349 in __libc_start_main
      15 0x5585cbbd2f54 in _start

Fixes: 137966e01fffe0 ("libobs-opengl: Try to use the platform display if available")
---
 libobs-opengl/gl-x11-egl.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/libobs-opengl/gl-x11-egl.c b/libobs-opengl/gl-x11-egl.c
index 908b3d882..fd5c1f3f2 100644
--- a/libobs-opengl/gl-x11-egl.c
+++ b/libobs-opengl/gl-x11-egl.c
@@ -82,6 +82,7 @@ struct gl_platform {
 	EGLConfig config;
 	EGLContext context;
 	EGLSurface pbuffer;
+	bool close_xdisplay;
 };
 
 /* The following utility function is copied verbatim from GLX code. */
@@ -269,15 +270,19 @@ static void gl_x11_egl_windowinfo_destroy(struct gl_windowinfo *info)
 	bfree(info);
 }
 
-static Display *open_windowless_display(Display *platform_display)
+static Display *open_windowless_display(bool *should_close)
 {
+	Display *platform_display = obs_get_nix_platform_display();
 	Display *display;
 	xcb_connection_t *xcb_conn;
 
-	if (platform_display)
+	if (platform_display) {
 		display = platform_display;
-	else
+		*should_close = false;
+	} else {
 		display = XOpenDisplay(NULL);
+		*should_close = true;
+	}
 
 	if (!display) {
 		blog(LOG_ERROR, "Unable to open new X connection!");
@@ -298,7 +303,8 @@ static Display *open_windowless_display(Display *platform_display)
 	return display;
 
 error:
-	XCloseDisplay(display);
+	if (*should_close)
+		XCloseDisplay(display);
 	return NULL;
 }
 
@@ -325,8 +331,7 @@ static struct gl_platform *gl_x11_egl_platform_create(gs_device_t *device,
 	   For an explanation see here: http://xcb.freedesktop.org/MixingCalls/
 	   Essentially, EGL requires Xlib. Everything else we use xcb. */
 	struct gl_platform *plat = bmalloc(sizeof(struct gl_platform));
-	Display *platform_display = obs_get_nix_platform_display();
-	Display *display = open_windowless_display(platform_display);
+	Display *display = open_windowless_display(&plat->close_xdisplay);
 
 	if (!display) {
 		goto fail_display_open;
@@ -363,7 +368,8 @@ fail_make_current:
 	gl_context_destroy(plat);
 fail_context_create:
 fail_load_gl:
-	XCloseDisplay(display);
+	if (plat->close_xdisplay)
+		XCloseDisplay(plat->xdisplay);
 fail_display_open:
 	bfree(plat);
 	plat = NULL;