Re: [PATCH v2 RESEND] coresight: etm-perf: Fix reference count leak in etm_setup_aux

[James Clark]

On 15/12/2025 04:27, 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@xxxxxxxxxxxxxxx
> Fixes: 0e6c20517596 ("coresight: etm-perf: Allow an event to use different sinks")
> Signed-off-by: Ma Ke <make24@xxxxxxxxxxx>
> ---
> Changes in v2:
> - modified the patch as suggestions.

I think Leo's comment on the previous v2 is still unaddressed. But 
releasing it in coresight_get_sink_by_id() would make it consistent with 
coresight_find_csdev_by_fwnode() and prevent further mistakes.

It also leads me to see that users of coresight_find_device_by_fwnode() 
should also release it, but only one out of two appears to.

James

> ---
>   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 17afa0f4cdee..56d012ab6d3a 100644
> --- a/drivers/hwtracing/coresight/coresight-etm-perf.c
> +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
> @@ -454,6 +454,11 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
>   		goto err;
>   
>   out:
> +	if (user_sink) {
> +		put_device(&user_sink->dev);
> +		user_sink = NULL;
> +	}
> +
>   	return event_data;
>   
>   err: