From:   Mukesh Ojha <quic_mojha@quicinc.com>
To:     <borrello@diag.uniroma1.it>
CC:     <c.giuffrida@vu.nl>, <h.j.bos@vu.nl>, <jkl820.git@gmail.com>,
        <linux-kernel@vger.kernel.org>,
        <linux-trace-kernel@vger.kernel.org>, <mhiramat@kernel.org>,
        <rostedt@goodmis.org>
Subject: Re: [PATCH] tracing/probe: trace_probe_primary_from_call(): checked list_first_entry
Date:   Fri, 17 Feb 2023 19:12:40 +0530
Message-ID: <1676641360-22701-1-git-send-email-quic_mojha@quicinc.com>
In-Reply-To: <20230128-list-entry-null-check-v1-1-8bde6a3da2ef@diag.uniroma1.it>
References: <20230128-list-entry-null-check-v1-1-8bde6a3da2ef@diag.uniroma1.it>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

>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@diag.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);
> }

Nice catch !!

Acked-by: Mukesh Ojha <quic_mojha@quicinc.com>

-Mukesh
> 
> static inline struct list_head *trace_probe_probe_list(struct trace_probe *tp)