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

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Date:   Mon, 11 Oct 2021 20:48:27 -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 virt-pci] Fix application of sizeof to pointer

On Tue, 2021-10-12 at 11:23 +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.
[]
> diff --git a/arch/um/drivers/virt-pci.c b/arch/um/drivers/virt-pci.c
[]
> @@ -189,7 +189,7 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
>  	buf = get_cpu_var(um_pci_msg_bufs);
>  	data = buf->data;
> 
> -	memset(data, 0xff, sizeof(data));
> +	memset(data, 0xff, sizeof(buf->data));

Perhaps change this to:

	memset(buf->data, 0xff, sizeof(buf->data));
	data = buf->data;

but honestly, the indirection to data doesn't make the code
much more readable so maybe just remove data altogether.
---
 arch/um/drivers/virt-pci.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/um/drivers/virt-pci.c b/arch/um/drivers/virt-pci.c
index c080666330234..75e05ead97b9a 100644
--- a/arch/um/drivers/virt-pci.c
+++ b/arch/um/drivers/virt-pci.c
@@ -180,7 +180,6 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
 	};
 	/* buf->data is maximum size - we may only use parts of it */
 	struct um_pci_message_buffer *buf;
-	u8 *data;
 	unsigned long ret = ~0ULL;
 
 	if (!dev)
@@ -189,7 +188,7 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
 	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: