android: fix segfault within swap_buffers

Function droid_swap_buffers may get called without dri2_surf->buffer set,
in these cases we don't have a back buffer set either. Patch fixes segfault
seen with 3DMark that uses android.opengl.GLSurfaceView for rendering it's UI.

backtrace:
   #00 pc 00013f88  /system/lib/egl/libGLES_mesa.so (droid_swap_buffers+104)
   #01 pc 000117b2  /system/lib/egl/libGLES_mesa.so (dri2_swap_buffers+50)
   #02 pc 000058b2  /system/lib/egl/libGLES_mesa.so (eglSwapBuffers+386)
   #03 pc 00011329  /system/lib/libEGL.so (eglSwapBuffersWithDamageKHR+553)
   #04 pc 000118e7  /system/lib/libEGL.so (eglSwapBuffers+55)
   #05 pc 000754dc  /system/lib/libandroid_runtime.so

v2: do like other backends, call get_back_bo (Emil Velikov)

Fixes: 2acc69d ("EGL/Android: Add EGL_EXT_buffer_age extension")
Signed-off-by: Tapani Pälli <[email protected]>
Reviewed-by: Emil Velikov <[email protected]>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/egl/drivers/dri2/platform_android.c b/src/egl/drivers/dri2/platform_android.c
index 14e13b8e85c..667e08b3451 100644
--- a/src/egl/drivers/dri2/platform_android.c
+++ b/src/egl/drivers/dri2/platform_android.c
@@ -634,6 +634,14 @@ droid_swap_buffers(_EGLDriver *drv, _EGLDisplay *disp, _EGLSurface *draw)
       if (dri2_surf->color_buffers[i].age > 0)
          dri2_surf->color_buffers[i].age++;
    }
+
+   /* Make sure we have a back buffer in case we're swapping without
+    * ever rendering. */
+   if (get_back_bo(dri2_surf, 0) < 0) {
+      _eglError(EGL_BAD_ALLOC, "dri2_swap_buffers");
+      return EGL_FALSE;
+   }
+
    dri2_surf->back->age = 1;
 
    dri2_flush_drawable_for_swapbuffers(disp, draw);