linux-kernel - Re: [PATCH v4] perf data convert: Fix segfault when converting to json when cpu

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Date: Sat, 24 Feb 2024 12:49:35 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Ilkka Koskinen <ilkka@...amperecomputing.com>
Cc: Namhyung Kim <namhyung@...nel.org>, James Clark <james.clark@....com>,
	Ian Rogers <irogers@...gle.com>,
	Evgeny Pistun <kotborealis@...oo.ru>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] perf data convert: Fix segfault when converting to
 json when cpu_desc isn't set

On Fri, Feb 23, 2024 at 02:04:58PM -0800, Ilkka Koskinen wrote:
> Arm64 doesn't have Model in /proc/cpuinfo and, thus, cpu_desc doesn't get
> assigned.
> 
> Running
> 	$ perf data convert --to-json perf.data.json
> 
> ends up calling output_json_string() with NULL pointer, which causes a
> segmentation fault.
> 
> Signed-off-by: Ilkka Koskinen <ilkka@...amperecomputing.com>

Acked-by: Arnaldo Carvalho de Melo <acme@...hat.com>

- Arnaldo

> ---
> 
> v1:
>     - https://lore.kernel.org/all/20240111232923.8138-1-ilkka@os.amperecomputing.com/
> v2:
>     - Changed the patch based on James's comments.
> v3:
>     - The architecture is checked from the actual data file to allow one to do
>       conversion on another system. (thanks to James for the feedback)
>     - https://lore.kernel.org/all/20240117215101.77713-1-ilkka@os.amperecomputing.com/
> v4:
>     - Made the fix more generic in case there are other architectures where cpu_desc
>       isn't assigned as asked by Namhyung
>     - Rephrased the subject line
> ---
> 
> tools/perf/util/data-convert-json.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/data-convert-json.c b/tools/perf/util/data-convert-json.c
> index 5bb3c2ba95ca..09d57efd2d9d 100644
> --- a/tools/perf/util/data-convert-json.c
> +++ b/tools/perf/util/data-convert-json.c
> @@ -284,7 +284,9 @@ static void output_headers(struct perf_session *session, struct convert_json *c)
>  	output_json_key_string(out, true, 2, "os-release", header->env.os_release);
>  	output_json_key_string(out, true, 2, "arch", header->env.arch);
>  
> -	output_json_key_string(out, true, 2, "cpu-desc", header->env.cpu_desc);
> +	if (header->env.cpu_desc)
> +		output_json_key_string(out, true, 2, "cpu-desc", header->env.cpu_desc);
> +
>  	output_json_key_string(out, true, 2, "cpuid", header->env.cpuid);
>  	output_json_key_format(out, true, 2, "nrcpus-online", "%u", header->env.nr_cpus_online);
>  	output_json_key_format(out, true, 2, "nrcpus-avail", "%u", header->env.nr_cpus_avail);
> -- 
> 2.43.0