linux-kernel - Re: [PATCH] tracing/kprobe: Release kprobe print

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Date:   Mon, 9 Jul 2018 12:44:16 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Song Liu <songliubraving@...com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Yonghong Song <yhs@...com>, Josef Bacik <jbacik@...com>,
        daniel@...earbox.net, davem@...emloft.net,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] tracing/kprobe: Release kprobe print_fmt properly

On Mon,  9 Jul 2018 16:19:06 +0200
Jiri Olsa <jolsa@...nel.org> wrote:

> We don't release tk->tp.call.print_fmt when destroying
> local uprobe. Also there's missing print_fmt kfree in
> create_local_trace_kprobe error path.
> 
> Fixes: e12f03d7031a ("perf/core: Implement the 'perf_kprobe' PMU")
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>

Thanks for the patch, I'm applying it now (and testing it).

> ---
>  kernel/trace/trace_kprobe.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index daa81571b22a..21f718472942 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -1480,8 +1480,10 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs,
>  	}
>  
>  	ret = __register_trace_kprobe(tk);
> -	if (ret < 0)
> +	if (ret < 0) {
> +		kfree(tk->tp.call.print_fmt);
>  		goto error;
> +	}
>  
>  	return &tk->tp.call;
>  error:
> @@ -1501,6 +1503,8 @@ void destroy_local_trace_kprobe(struct trace_event_call *event_call)
>  	}
>  
>  	__unregister_trace_kprobe(tk);
> +
> +	kfree(tk->tp.call.print_fmt);

Bah! The naming convention of "set_print_fmt()" is horrible, and leads
to these kinds of bugs. I'll make a patch (not for stable though) that
makes it a bit more obvious to what is happening.

-- Steve


>  	free_trace_kprobe(tk);
>  }
>  #endif /* CONFIG_PERF_EVENTS */