linux-kernel - Re: [PATCH v2] crypto: ccp: Use scoped guard for mutex

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Message-ID: <06162594-21e8-e850-a179-cc42ac5a4c53@amd.com>
Date: Mon, 2 Dec 2024 08:43:00 -0600
From: Tom Lendacky <thomas.lendacky@....com>
To: Mario Limonciello <mario.limonciello@....com>,
 Herbert Xu <herbert@...dor.apana.org.au>
Cc: John Allen <john.allen@....com>,
 "open list:AMD CRYPTOGRAPHIC COPROCESSOR (CCP) DRIVER - DB..."
 <linux-crypto@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] crypto: ccp: Use scoped guard for mutex

On 11/30/24 07:58, Mario Limonciello wrote:
> Use a scoped guard to simplify the cleanup handling.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
> v2:
>  * return immediately in default case
> ---
>  drivers/crypto/ccp/dbc.c | 53 ++++++++++++++--------------------------
>  1 file changed, 19 insertions(+), 34 deletions(-)
> 
> diff --git a/drivers/crypto/ccp/dbc.c b/drivers/crypto/ccp/dbc.c
> index 5b105a23f6997..a3c6822b3829a 100644
> --- a/drivers/crypto/ccp/dbc.c
> +++ b/drivers/crypto/ccp/dbc.c
> @@ -7,6 +7,8 @@
>   * Author: Mario Limonciello <mario.limonciello@....com>
>   */
>  
> +#include <linux/mutex.h>
> +
>  #include "dbc.h"
>  
>  #define DBC_DEFAULT_TIMEOUT		(10 * MSEC_PER_SEC)
> @@ -137,64 +139,47 @@ static long dbc_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>  		return -ENODEV;
>  	dbc_dev = psp_master->dbc_data;
>  
> -	mutex_lock(&dbc_dev->ioctl_mutex);
> +	guard(mutex)(&dbc_dev->ioctl_mutex);
>  
>  	switch (cmd) {
>  	case DBCIOCNONCE:
> -		if (copy_from_user(dbc_dev->payload, argp, sizeof(struct dbc_user_nonce))) {
> -			ret = -EFAULT;
> -			goto unlock;
> -		}
> +		if (copy_from_user(dbc_dev->payload, argp, sizeof(struct dbc_user_nonce)))
> +			return -EFAULT;
>  
>  		ret = send_dbc_nonce(dbc_dev);
>  		if (ret)
> -			goto unlock;
> +			return ret;
>  
> -		if (copy_to_user(argp, dbc_dev->payload, sizeof(struct dbc_user_nonce))) {
> -			ret = -EFAULT;
> -			goto unlock;
> -		}
> +		if (copy_to_user(argp, dbc_dev->payload, sizeof(struct dbc_user_nonce)))
> +			return -EFAULT;
>  		break;
>  	case DBCIOCUID:
> -		if (copy_from_user(dbc_dev->payload, argp, sizeof(struct dbc_user_setuid))) {
> -			ret = -EFAULT;
> -			goto unlock;
> -		}
> +		if (copy_from_user(dbc_dev->payload, argp, sizeof(struct dbc_user_setuid)))
> +			return -EFAULT;
>  
>  		*dbc_dev->payload_size = dbc_dev->header_size + sizeof(struct dbc_user_setuid);
>  		ret = send_dbc_cmd(dbc_dev, PSP_DYNAMIC_BOOST_SET_UID);
>  		if (ret)
> -			goto unlock;
> +			return ret;
>  
> -		if (copy_to_user(argp, dbc_dev->payload, sizeof(struct dbc_user_setuid))) {
> -			ret = -EFAULT;
> -			goto unlock;
> -		}
> +		if (copy_to_user(argp, dbc_dev->payload, sizeof(struct dbc_user_setuid)))
> +			return -EFAULT;
>  		break;
>  	case DBCIOCPARAM:
> -		if (copy_from_user(dbc_dev->payload, argp, sizeof(struct dbc_user_param))) {
> -			ret = -EFAULT;
> -			goto unlock;
> -		}
> +		if (copy_from_user(dbc_dev->payload, argp, sizeof(struct dbc_user_param)))
> +			return -EFAULT;
>  
>  		*dbc_dev->payload_size = dbc_dev->header_size + sizeof(struct dbc_user_param);
>  		ret = send_dbc_parameter(dbc_dev);
>  		if (ret)
> -			goto unlock;
> +			return ret;
>  
> -		if (copy_to_user(argp, dbc_dev->payload, sizeof(struct dbc_user_param)))  {
> -			ret = -EFAULT;
> -			goto unlock;
> -		}
> +		if (copy_to_user(argp, dbc_dev->payload, sizeof(struct dbc_user_param)))
> +			return -EFAULT;
>  		break;
> -	default:
> -		ret = -EINVAL;
> -
>  	}
> -unlock:
> -	mutex_unlock(&dbc_dev->ioctl_mutex);
>  
> -	return ret;
> +	return -EINVAL;

Hmmm... not quite what I said when I said to put a return -EINVAL in the
default case. You now return -EINVAL for every successful case.

Thanks,
Tom

>  }
>  
>  static const struct file_operations dbc_fops = {