[Mesa-stable] [PATCH] i965: Fix crash when calling glViewport with no surface bound

[Neil Roberts]

If EGL_KHR_surfaceless_context is used then glViewport can be called
with NULL for the draw and read surfaces. This was previously causing
a crash because the i965 driver tries to use this point to invalidate
the surfaces and it was derferencing the NULL pointer.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93257
Cc: Nanley Chery <nanley.g.chery at intel.com>
Cc: "11.1" <mesa-stable at lists.freedesktop.org>
---

I've also posted a Piglit test for this here:

http://patchwork.freedesktop.org/patch/67356/

 src/mesa/drivers/dri/i965/brw_context.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c
index 7d7643c..5374bad 100644
--- a/src/mesa/drivers/dri/i965/brw_context.c
+++ b/src/mesa/drivers/dri/i965/brw_context.c
@@ -159,8 +159,10 @@ intel_viewport(struct gl_context *ctx)
    __DRIcontext *driContext = brw->driContext;
 
    if (_mesa_is_winsys_fbo(ctx->DrawBuffer)) {
-      dri2InvalidateDrawable(driContext->driDrawablePriv);
-      dri2InvalidateDrawable(driContext->driReadablePriv);
+      if (driContext->driDrawablePriv)
+         dri2InvalidateDrawable(driContext->driDrawablePriv);
+      if (driContext->driReadablePriv)
+         dri2InvalidateDrawable(driContext->driReadablePriv);
    }
 }
 
-- 
1.9.3