drm/vmwgfx: integer underflow in vmw_cmd_dx_set_shader() leading to an invalid read

commit 5ed7f4b5eca11c3c69e7c8b53e4321812bc1ee1e upstream.

If SVGA_3D_CMD_DX_SET_SHADER is called with a shader ID
of SVGA3D_INVALID_ID, and a shader type of
SVGA3D_SHADERTYPE_INVALID, the calculated binding.shader_slot
will be 4294967295, leading to an out-of-bounds read in vmw_binding_loc()
when the offset is calculated.

Cc: <stable@vger.kernel.org>
Fixes: d80efd5c ("drm/vmwgfx: Initial DX support")
Signed-off-by: NMurray McAllister <murray.mcallister@gmail.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: NThomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c

@@ -2493,7 +2493,8 @@ static int vmw_cmd_dx_set_shader(struct vmw_private *dev_priv,
 
 	cmd = container_of(header, typeof(*cmd), header);
 
-	if (cmd->body.type >= SVGA3D_SHADERTYPE_DX10_MAX) {
+	if (cmd->body.type >= SVGA3D_SHADERTYPE_DX10_MAX ||
+	    cmd->body.type < SVGA3D_SHADERTYPE_MIN) {
 		DRM_ERROR("Illegal shader type %u.\n",
 			  (unsigned) cmd->body.type);
 		return -EINVAL;