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

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Message-ID: <1676641360-22701-1-git-send-email-quic_mojha@quicinc.com>
Date:   Fri, 17 Feb 2023 19:12:40 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     <borrello@...g.uniroma1.it>
CC:     <c.giuffrida@...nl>, <h.j.bos@...nl>, <jkl820.git@...il.com>,
        <linux-kernel@...r.kernel.org>,
        <linux-trace-kernel@...r.kernel.org>, <mhiramat@...nel.org>,
        <rostedt@...dmis.org>
Subject: Re: [PATCH] tracing/probe: trace_probe_primary_from_call(): checked list_first_entry

>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);
> }

Nice catch !!

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

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