linux-kernel - Re: [PATCH] tracing/probe: trace_probe_primary_from_call(): checked list_first

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Message-ID: <20230130101947.311010c2@gandalf.local.home>
Date:   Mon, 30 Jan 2023 10:19:47 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Pietro Borrello <borrello@...g.uniroma1.it>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>, Jakob Koschel <jkl820.git@...il.com>,
        linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing/probe: trace_probe_primary_from_call(): checked
 list_first_entry

On Sat, 28 Jan 2023 16:23:41 +0000
Pietro Borrello <borrello@...g.uniroma1.it> wrote:

> All callers of trace_probe_primary_from_call() check the return
> value to be non NULL. However, the function returns
> list_first_entry(&tpe->probes, ...) which can never be NULL.
> Additionally, it does not check for the list being possibly empty,
> possibly causing a type confusion on empty lists.
> Use list_first_entry_or_null() which solves both problems.
> 
> Fixes: 60d53e2c3b75 ("tracing/probe: Split trace_event related data from trace_probe")
> Signed-off-by: Pietro Borrello <borrello@...g.uniroma1.it>
> ---
>  kernel/trace/trace_probe.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
> index 23acfd1c3812..f6b565dced56 100644
> --- a/kernel/trace/trace_probe.h
> +++ b/kernel/trace/trace_probe.h
> @@ -307,7 +307,7 @@ trace_probe_primary_from_call(struct trace_event_call *call)
>  {
>  	struct trace_probe_event *tpe = trace_probe_event_from_call(call);
>  
> -	return list_first_entry(&tpe->probes, struct trace_probe, list);
> +	return list_first_entry_or_null(&tpe->probes, struct trace_probe, list);
>  }
>  
>  static inline struct list_head *trace_probe_probe_list(struct trace_probe *tp)

Reviewed-by: Steven Rostedt (Google) <rostedt@...dmis.org>

-- Steve

> 
> ---
> base-commit: 2241ab53cbb5cdb08a6b2d4688feb13971058f65
> change-id: 20230128-list-entry-null-check-37778efda18c
> 
> Best regards,