linux-kernel - Re: [PATCH v2 1/4] perf: Allow using AUX data in perf samples

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Date:   Thu, 24 Oct 2019 16:01:39 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        jolsa@...hat.com, adrian.hunter@...el.com,
        mathieu.poirier@...aro.org, mark.rutland@....com
Subject: Re: [PATCH v2 1/4] perf: Allow using AUX data in perf samples

On Tue, Oct 22, 2019 at 12:58:09PM +0300, Alexander Shishkin wrote:
> @@ -11213,6 +11367,9 @@ SYSCALL_DEFINE5(perf_event_open,
>  	if (event->attr.aux_output && !perf_get_aux_event(event, group_leader))
>  		goto err_locked;
>  
> +	if (event->attr.aux_sample_size && !perf_get_aux_event(event, group_leader))
> +		goto err_locked;
> +

Either aux_sample_size and aux_output are mutually exclusive, or you're
leaking a refcount on group_leader. The first wants a check, the second
wants error path fixes.

>  	/*
>  	 * Must be under the same ctx::mutex as perf_install_in_context(),
>  	 * because we need to serialize with concurrent event creation.