Re: [PATCH] tracing: Fix NULL pointer dereference in start_creating

[Steven Rostedt]

On Fri, 30 Jul 2021 18:53:06 +0530
Kamal Agrawal <kamaagra@xxxxxxxxxxxxxx> wrote:

> The event_trace_add_tracer() can fail. In this case, it leads to a crash
> in start_creating with below call stack. Handle the error scenario
> properly in trace_array_create_dir.
> 
> Call trace:
> down_write+0x7c/0x204
> start_creating.25017+0x6c/0x194
> tracefs_create_file+0xc4/0x2b4
> init_tracer_tracefs+0x5c/0x940
> trace_array_create_dir+0x58/0xb4
> trace_array_create+0x1bc/0x2b8
> trace_array_get_by_name+0xdc/0x18c
> 
> Fixes: 4114fbfd

Thanks, I'll queue this up.

-- Steve

> Signed-off-by: Kamal Agrawal <kamaagra@xxxxxxxxxxxxxx>
> ---
>  kernel/trace/trace.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index c59dd35..33899a7 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -9135,8 +9135,10 @@ static int trace_array_create_dir(struct trace_array *tr)
>  		return -EINVAL;
>  
>  	ret = event_trace_add_tracer(tr->dir, tr);
> -	if (ret)
> +	if (ret) {
>  		tracefs_remove(tr->dir);
> +		return ret;
> +	}
>  
>  	init_tracer_tracefs(tr, tr->dir);
>  	__update_tracer_options(tr);