linux-kernel - Re: [PATCH v4 1/2] coresight: Fix fwnode leak in coresight

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Message-ID: <20250922100653.GE516577@e132581.arm.com>
Date: Mon, 22 Sep 2025 11:06:53 +0100
From: Leo Yan <leo.yan@....com>
To: Sean Anderson <sean.anderson@...ux.dev>
Cc: Suzuki K Poulose <suzuki.poulose@....com>, coresight@...ts.linaro.org,
	linux-arm-kernel@...ts.infradead.org,
	James Clark <james.clark@...aro.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Yeoreum Yun <yeoreum.yun@....com>,
	Linu Cherian <lcherian@...vell.com>,
	Mike Leach <mike.leach@...aro.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/2] coresight: Fix fwnode leak in coresight_register
 error path

On Fri, Sep 19, 2025 at 12:06:52PM -0400, Sean Anderson wrote:
> If registering the CPU map fails, we need to put the fwnode. free_percpu
> works when called with a NULL pointer, so just use
> coresight_device_release.
> 
> Fixes: 5ad628a76176 ("coresight: Use per-sink trace ID maps for Perf sessions")
> Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>

I have a patch that fixes the same issue:

https://lore.kernel.org/linux-arm-kernel/20250512154108.23920-2-leo.yan@arm.com/

The difference in my patch is about the sequence: first it allocates the
resource, then increases the fw node's reference count. During release,
it first decreases the reference count, and then safely releases the
resource.

After comparing your patch, I still think the above reason is valid.

That said, I agree we should put this fixing before the panic notifier
fix. This would be friendly for backporting.

Thanks,
Leo

> ---
> 
> Changes in v4:
> - New
> 
>  drivers/hwtracing/coresight/coresight-core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index fa758cc21827..022c8384b98d 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -1352,7 +1352,7 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
>  		raw_spin_lock_init(&csdev->perf_sink_id_map.lock);
>  		csdev->perf_sink_id_map.cpu_map = alloc_percpu(atomic_t);
>  		if (!csdev->perf_sink_id_map.cpu_map) {
> -			kfree(csdev);
> +			coresight_device_release(&csdev->dev);
>  			ret = -ENOMEM;
>  			goto err_out;
>  		}
> -- 
> 2.35.1.1320.gc452695387.dirty
>