st/mesa: fix glReadBuffer(GL_NONE) segfault

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=73956
Cc: 10.0 <mesa-stable@lists.freedesktop.org>
Tested-by: Ahmed Allam <ahmabdabd@hotmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>

diff --git a/src/mesa/state_tracker/st_cb_fbo.c b/src/mesa/state_tracker/st_cb_fbo.c
index 637f7ee9897b6e960b4c5ddaa07bb229621b3d23..eca04b89b5acda5de918da2247074593c9322077 100644 (file)
--- a/src/mesa/state_tracker/st_cb_fbo.c
+++ b/src/mesa/state_tracker/st_cb_fbo.c
@@ -700,7 +700,8 @@ st_ReadBuffer(struct gl_context *ctx, GLenum buffer)
    (void) buffer;
 
    /* add the renderbuffer on demand */
-   st_manager_add_color_renderbuffer(st, fb, fb->_ColorReadBufferIndex);
+   if (fb->_ColorReadBufferIndex >= 0)
+      st_manager_add_color_renderbuffer(st, fb, fb->_ColorReadBufferIndex);
 }