(In reply to zzyxpaw from comment #52)
> Created attachment 141522 [details]
> Logs + trace with patched mesa, plus example code which consistently
> triggers crash.
> 

The example code is incorrect. Line 99: 
   glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5*sizeof(float),
&vertices[3]);
Should be:
   glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5*sizeof(float), 3 *
sizeof(float));

(cf glVertexAttribPointer documentation: "pointer is treated as a byte offset
into the buffer object's data store")

With this change the program runs correctly.

Note that even if the program is invalid it shouldn't hang the GPU. I'm working
on a fix for this.