linux-kernel - Re: [PATCH v5 5/5] tracing/probes: Fix to record 0-length data_loc in fetch_store

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Message-ID: <20230711122206.531a6504@gandalf.local.home>
Date:   Tue, 11 Jul 2023 12:22:06 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc:     Dan Carpenter <dan.carpenter@...aro.org>,
        linux-trace-kernel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 5/5] tracing/probes: Fix to record 0-length data_loc
 in fetch_store_string*() if fails

On Tue, 11 Jul 2023 23:16:07 +0900
"Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:

> From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> 
> Fix to record 0-length data to data_loc in fetch_store_string*() if it fails
> to get the string data.
> Currently those expect that the data_loc is updated by store_trace_args() if
> it returns the error code. However, that does not work correctly if the
> argument is an array of strings. In that case, store_trace_args() only clears
> the first entry of the array (which may have no error) and leaves other
> entries. So it should be cleared by fetch_store_string*() itself.
> Also, 'dyndata' and 'maxlen' in store_trace_args() should be updated
> only if it is used (ret > 0 and argument is a dynamic data.)
> 
> Fixes: 40b53b771806 ("tracing: probeevent: Add array type support")
> Cc: stable@...r.kernel.org
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> ---
>  Changes in v4:
>   - Simplify the updating data_loc code with set_data_loc().
>  Changes in v5:
>   - Move out arg->dynamic check from unlikely() and use likely().
> ---
>  kernel/trace/trace_probe_kernel.h |   13 +++++++++----
>  kernel/trace/trace_probe_tmpl.h   |   10 +++-------
>  kernel/trace/trace_uprobe.c       |    3 ++-
>  3 files changed, 14 insertions(+), 12 deletions(-)
> 


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

-- Steve