linux-kernel - Re: [PATCH] coresight: syscfg: Fix memleak on registration failure in cscfg_create

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Date:   Thu, 20 Jan 2022 10:56:42 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Miaoqian Lin <linmq006@...il.com>
Cc:     Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] coresight: syscfg: Fix memleak on registration failure
 in cscfg_create_device

Good morning,

On Mon, Jan 10, 2022 at 07:31:00AM +0000, Miaoqian Lin wrote:
> device_register() calls device_initialize(),
> according to doc of device_initialize:
> 
>     Use put_device() to give up your reference instead of freeing
>     * @dev directly once you have called this function.

That is _if_ device_initialize() is called manually.  In this instance
@dev is registered with device_register() and unregistered with
device_unregister().  The latter conforms to the comment you pointed out and
calls put_device() as expected.

Thanks,
Mathieu

> 
> To prevent potential memleak, use put_device() instead call kfree
> directly.
> 
> Signed-off-by: Miaoqian Lin <linmq006@...il.com>
> ---
>  drivers/hwtracing/coresight/coresight-syscfg.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c
> index 43054568430f..007fa1c761a7 100644
> --- a/drivers/hwtracing/coresight/coresight-syscfg.c
> +++ b/drivers/hwtracing/coresight/coresight-syscfg.c
> @@ -764,7 +764,7 @@ struct device *cscfg_device(void)
>  /* Must have a release function or the kernel will complain on module unload */
>  static void cscfg_dev_release(struct device *dev)
>  {
> -	kfree(cscfg_mgr);
> +	put_device(dev);
>  	cscfg_mgr = NULL;
>  }
>  
> -- 
> 2.17.1
>