linux-kernel - Re: [PATCH] nfc: Fix potential resource leaks

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Date:   Wed, 21 Dec 2022 10:45:29 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Miaoqian Lin <linmq006@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Samuel Ortiz <sameo@...ux.intel.com>,
        Christophe Ricard <christophe.ricard@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nfc: Fix potential resource leaks

On 20/12/2022 14:46, Miaoqian Lin wrote:
> nfc_get_device() take reference for the device, add missing
> nfc_put_device() to release it when not need anymore.
> Also fix the style warnning by use error EOPNOTSUPP instead of
> ENOTSUPP.
> 
> Fixes: 5ce3f32b5264 ("NFC: netlink: SE API implementation")
> Fixes: 29e76924cf08 ("nfc: netlink: Add capability to reply to vendor_cmd with data")
> Signed-off-by: Miaoqian Lin <linmq006@...il.com>
> ---
>  net/nfc/netlink.c | 51 ++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 37 insertions(+), 14 deletions(-)
> 
> diff --git a/net/nfc/netlink.c b/net/nfc/netlink.c
> index 9d91087b9399..d081beaf4828 100644
> --- a/net/nfc/netlink.c
> +++ b/net/nfc/netlink.c
> @@ -1497,6 +1497,7 @@ static int nfc_genl_se_io(struct sk_buff *skb, struct genl_info *info)
>  	u32 dev_idx, se_idx;
>  	u8 *apdu;
>  	size_t apdu_len;
> +	int error;

Let's don't introduce the third or fourth style. Existing code calls it
"rc".

>  
>  	if (!info->attrs[NFC_ATTR_DEVICE_INDEX] ||
>  	    !info->attrs[NFC_ATTR_SE_INDEX] ||
> @@ -1510,25 +1511,37 @@ static int nfc_genl_se_io(struct sk_buff *skb, struct genl_info *info)
>  	if (!dev)
>  		return -ENODEV;
>  
> -	if (!dev->ops || !dev->ops->se_io)
> -		return -ENOTSUPP;
> +	if (!dev->ops || !dev->ops->se_io) {
> +		error = -EOPNOTSUPP;
> +		goto put_dev;
> +	}
>  
>  	apdu_len = nla_len(info->attrs[NFC_ATTR_SE_APDU]);
> -	if (apdu_len == 0)
> -		return -EINVAL;
> +	if (apdu_len == 0) {
> +		error = -EINVAL;
> +		goto put_dev;
> +	}
>  
>  	apdu = nla_data(info->attrs[NFC_ATTR_SE_APDU]);
> -	if (!apdu)
> -		return -EINVAL;
> +	if (!apdu) {
> +		error = -EINVAL;
> +		goto put_dev;
> +	}
>  
>  	ctx = kzalloc(sizeof(struct se_io_ctx), GFP_KERNEL);
> -	if (!ctx)
> -		return -ENOMEM;
> +	if (!ctx) {
> +		error = -ENOMEM;
> +		goto put_dev;
> +	}
>  
>  	ctx->dev_idx = dev_idx;
>  	ctx->se_idx = se_idx;
>  
> -	return nfc_se_io(dev, se_idx, apdu, apdu_len, se_io_cb, ctx);
> +	error = nfc_se_io(dev, se_idx, apdu, apdu_len, se_io_cb, ctx);
> +
> +put_dev:
> +	nfc_put_device(dev);
> +	return error;
>  }
>  
>  static int nfc_genl_vendor_cmd(struct sk_buff *skb,
> @@ -1551,14 +1564,20 @@ static int nfc_genl_vendor_cmd(struct sk_buff *skb,
>  	subcmd = nla_get_u32(info->attrs[NFC_ATTR_VENDOR_SUBCMD]);
>  
>  	dev = nfc_get_device(dev_idx);
> -	if (!dev || !dev->vendor_cmds || !dev->n_vendor_cmds)
> +	if (!dev)
>  		return -ENODEV;

Blank line

> +	if (!dev->vendor_cmds || !dev->n_vendor_cmds) {
> +		err = -ENODEV;
> +		goto put_dev;
> +	}
>  
>  	if (info->attrs[NFC_ATTR_VENDOR_DATA]) {
>  		data = nla_data(info->attrs[NFC_ATTR_VENDOR_DATA]);
>  		data_len = nla_len(info->attrs[NFC_ATTR_VENDOR_DATA]);
> -		if (data_len == 0)
> -			return -EINVAL;
> +		if (data_len == 0) {
> +			err = -EINVAL;
> +			goto put_dev;
> +		}
>  	} else {
>  		data = NULL;
>  		data_len = 0;
> @@ -1573,10 +1592,14 @@ static int nfc_genl_vendor_cmd(struct sk_buff *skb,
>  		dev->cur_cmd_info = info;
>  		err = cmd->doit(dev, data, data_len);
>  		dev->cur_cmd_info = NULL;
> -		return err;
> +		goto put_dev;
>  	}
>  
> -	return -EOPNOTSUPP;
> +	err = -EOPNOTSUPP;
> +
> +put_dev:
> +	nfc_put_device(dev);
> +	return err;
>  }
>  
>  /* message building helper */

Best regards,
Krzysztof