linux-kernel - Re: [PATCH v2] Fix application of sizeof to pointer

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Date:   Tue, 12 Oct 2021 00:01:58 -0700
From:   Joe Perches <joe@...ches.com>
To:     davidcomponentone@...il.com, jdike@...toit.com
Cc:     richard@....at, anton.ivanov@...bridgegreys.com,
        johannes.berg@...el.com, linux-um@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Zeal Robot <zealci@....com.cn>
Subject: Re: [PATCH v2] Fix application of sizeof to pointer

On Tue, 2021-10-12 at 14:50 +0800, davidcomponentone@...il.com wrote:
> From: David Yang <davidcomponentone@...il.com>
> 
> The coccinelle check report:
> "./arch/um/drivers/virt-pci.c:192:20-26:
> ERROR: application of sizeof to pointer"
> Using the "sizeof(buf->data)" to fix it.

Try compiling this with W=1 or just maybe even just compiling your change.
You've now got an unused declaration of u8 *data;
 
> diff --git a/arch/um/drivers/virt-pci.c b/arch/um/drivers/virt-pci.c
[]
> @@ -187,9 +187,8 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
>  		return ~0ULL;
> 
>  	buf = get_cpu_var(um_pci_msg_bufs);
> -	data = buf->data;
> 
> -	memset(data, 0xff, sizeof(data));
> +	memset(buf->data, 0xff, sizeof(buf->data));
>  	switch (size) {
>  	case 1:
> @@ -204,22 +203,22 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
>  		goto out;
>  	}
> 
> -	if (um_pci_send_cmd(dev, &hdr, sizeof(hdr), NULL, 0, data, 8))
> +	if (um_pci_send_cmd(dev, &hdr, sizeof(hdr), NULL, 0, buf->data, 8))
>  		goto out;
> 
>  	switch (size) {
>  	case 1:
> -		ret = data[0];
> +		ret = buf->data[0];
>  		break;
>  	case 2:
> -		ret = le16_to_cpup((void *)data);
> +		ret = le16_to_cpup((void *)buf->data);
>  		break;
>  	case 4:
> -		ret = le32_to_cpup((void *)data);
> +		ret = le32_to_cpup((void *)buf->data);
>  		break;
>  #ifdef CONFIG_64BIT
>  	case 8:
> -		ret = le64_to_cpup((void *)data);
> +		ret = le64_to_cpup((void *)buf->data);
>  		break;
>  #endif
>  	default: