Re: [PATCH v5 11/34] function_graph: Have the instances use their own ftrace_ops for filtering

[Google]

Hi,

On Mon, 18 Dec 2023 22:13:46 +0900
"Masami Hiramatsu (Google)" <mhiramat@xxxxxxxxxx> wrote:

> @@ -408,15 +395,51 @@ int function_graph_enter(unsigned long ret, unsigned long func,
>  	return -EBUSY;
>  }
>  
> +/* This is called from ftrace_graph_func() via ftrace */
> +int function_graph_enter_ops(unsigned long ret, unsigned long func,
> +			     unsigned long frame_pointer, unsigned long *retp,
> +			     struct fgraph_ops *gops)
> +{
> +	struct ftrace_graph_ent trace;
> +	int index;
> +	int type;
> +

Here,  I found that this needs to check whether the fgraph_array[gops->idx]
is still valid or not. When unregistering the fgraph, fgraph_array[idx] is
cleared (with fgraph_stub) and disable ftrace. So there is a chance to hit
this and it will mess up the shadow stack because gops->idx is already invalid.

Thank you,

-- 
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>