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SubjectRe: [PATCH 3/8] rtla/osnoise_top: Fix segmentation fault when failing to enable -t
On Mon, 24 Jan 2022 15:24:06 +0100
Daniel Bristot de Oliveira <bristot@kernel.org> wrote:

> rtla osnoise top is causing a segmentation fault when running with
> the --trace option on a kernel that does not support multiple
> instances. For example:
>
> [root@f34 rtla]# rtla osnoise top -t
> failed to enable the tracer osnoise
> Could not enable osnoiser tracer for tracing
> Failed to enable the trace instance
> Segmentation fault (core dumped)
>
> This error happens because the exit code of the tools is trying
> to destroy the trace instance that failed to be created.
>
> Rearrange the order in which trace instances are destroyed to avoid
> this problem.
>
> Fixes: 1eceb2fc2ca5 ("rtla/osnoise: Add osnoise top mode")
> Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-trace-devel@vger.kernel.org
> Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
> ---
> tools/tracing/rtla/src/osnoise_top.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/tools/tracing/rtla/src/osnoise_top.c b/tools/tracing/rtla/src/osnoise_top.c
> index 332b2ac205fc..546769bc7ff7 100644
> --- a/tools/tracing/rtla/src/osnoise_top.c
> +++ b/tools/tracing/rtla/src/osnoise_top.c
> @@ -546,7 +546,7 @@ int osnoise_top_main(int argc, char **argv)
> trace);
> if (retval < 0) {
> err_msg("Error iterating on events\n");
> - goto out_top;
> + goto out_trace;
> }
>
> if (!params->quiet)
> @@ -569,11 +569,12 @@ int osnoise_top_main(int argc, char **argv)
> }
> }
>
> +out_trace:
> + if (params->trace_output)
> + osnoise_destroy_tool(record);
> out_top:
> osnoise_free_top(tool->data);
> osnoise_destroy_tool(tool);
> - if (params->trace_output)
> - osnoise_destroy_tool(record);

Wouldn't these four patches be more robust if you just initialized record
(and tool) to NULL, and change osnoise_destroy_tool() to:

void osnoise_destroy_tool(struct osnoise_tool *top)
{
if (!top)
return;

trace_instance_destroy(&top->trace);

if (top->context)
osnoise_put_context(top->context);

free(top);
}

Then you don't need these extra labels and if statements in the main code.

-- Steve


> out_exit:
> exit(return_value);
> }

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