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

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Message-ID: <c698d581-da15-42bf-9612-62f1bad66615@linaro.org>
Date: Mon, 15 Dec 2025 11:02:08 +0200
From: James Clark <james.clark@...aro.org>
To: Ma Ke <make24@...as.ac.cn>, Leo Yan <leo.yan@....com>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
 stable@...r.kernel.org, suzuki.poulose@....com, mike.leach@...aro.org,
 alexander.shishkin@...ux.intel.com, mathieu.poirier@...aro.org
Subject: Re: [PATCH v2 RESEND] coresight: etm-perf: Fix reference count leak
 in etm_setup_aux



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@...r.kernel.org
> Fixes: 0e6c20517596 ("coresight: etm-perf: Allow an event to use different sinks")
> Signed-off-by: Ma Ke <make24@...as.ac.cn>
> ---
> 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: