drm/vmwgfx: Fix compat mode shader operation

commit e41c20cf upstream.

In compat mode, we allowed host-backed user-space with guest-backed
kernel / device. In this mode, set shader commands was broken since
no relocations were emitted. Fix this.

Cc: <stable@vger.kernel.org>
Fixes: e8c66efb ("drm/vmwgfx: Make user resource lookups reference-free during validation")
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c

@@ -2129,6 +2129,11 @@ static int vmw_cmd_set_shader(struct vmw_private *dev_priv,
 		return 0;
 
 	if (cmd->body.shid != SVGA3D_INVALID_ID) {
+		/*
+		 * This is the compat shader path - Per device guest-backed
+		 * shaders, but user-space thinks it's per context host-
+		 * backed shaders.
+		 */
 		res = vmw_shader_lookup(vmw_context_res_man(ctx),
 					cmd->body.shid,
 					cmd->body.type);
@@ -2137,6 +2142,14 @@ static int vmw_cmd_set_shader(struct vmw_private *dev_priv,
 			ret = vmw_execbuf_res_noctx_val_add(sw_context, res);
 			if (unlikely(ret != 0))
 				return ret;
+
+			ret = vmw_resource_relocation_add
+				(sw_context, res,
+				 vmw_ptr_diff(sw_context->buf_start,
+					      &cmd->body.shid),
+				 vmw_res_rel_normal);
+			if (unlikely(ret != 0))
+				return ret;
 		}
 	}