Re: [PATCH] coresight: etm-perf: Fix reference count leak in etm_setup_aux

[Suzuki K Poulose <suzuki.poulose@arm.com>]

Hi

On 11/11/2025 14:42, Ma Ke wrote:
> In etm_setup_aux(), when a user sink is obtained via
> coresight_get_sink_by_id(), it increments the reference count of the
> sink device. However, if the sink is used in path building, the path
> holds a reference, but the initial reference from
> coresight_get_sink_by_id() is not released, causing a reference count
> leak. We should release the initial reference after the path is built.
> 
> Found by code review.
> 
> Cc: stable@vger.kernel.org
> Fixes: 0e6c20517596 ("coresight: etm-perf: Allow an event to use different sinks")
> Signed-off-by: Ma Ke <make24@iscas.ac.cn>
> ---
>   drivers/hwtracing/coresight/coresight-etm-perf.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
> index f677c08233ba..6584f6aa87bf 100644
> --- a/drivers/hwtracing/coresight/coresight-etm-perf.c
> +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
> @@ -453,6 +453,11 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
>   	if (!event_data->snk_config)
>   		goto err;
>   
> +	if (user_sink) {
> +		put_device(&user_sink->dev);
> +		user_sink = NULL;
> +	}
> +

I would recommend moving this to the out: label below, to make sure
we drop the refcount even in the error path.

Otherwise looks good to me.

Suzuki

>   out:
>   	return event_data;
>