[Mesa-dev] [PATCH] android: fix segfault within swap_buffers

[Emil Velikov]

On 6 March 2017 at 12:27, Tapani Pälli <tapani.palli at intel.com> wrote:
> 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
>
> Fixes: 2acc69d ("EGL/Android: Add EGL_EXT_buffer_age extension")
> Signed-off-by: Tapani Pälli <tapani.palli at intel.com>
> ---
>  src/egl/drivers/dri2/platform_android.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/src/egl/drivers/dri2/platform_android.c b/src/egl/drivers/dri2/platform_android.c
> index 14e13b8..d2769b8 100644
> --- a/src/egl/drivers/dri2/platform_android.c
> +++ b/src/egl/drivers/dri2/platform_android.c
> @@ -634,7 +634,9 @@ droid_swap_buffers(_EGLDriver *drv, _EGLDisplay *disp, _EGLSurface *draw)
>        if (dri2_surf->color_buffers[i].age > 0)
>           dri2_surf->color_buffers[i].age++;
>     }
> -   dri2_surf->back->age = 1;
> +
> +   if (dri2_surf->back)
> +      dri2_surf->back->age = 1;
>
It seems like we're papering over the problem:

Both wayland and drm call get_back_bo() prior to touching
dri2_surf->back. Why we don't want to do the same here ?
Seems like my "we want to unify the implementations [or bad things
might happen]" kicked in earlier than expected :-\

-Emil