hwmon: (corsair-cpro) Validate the size of the received input buffer

Add buffer_recv_size to store the size of the received bytes.
Validate buffer_recv_size in send_usb_cmd().

Reported-by: syzbot+3bbbade4e1a7ab45ca3b@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-hwmon/61233ba1-e5ad-4d7a-ba31-3b5d0adcffcc@roeck-us.net
Fixes: 40c3a44 ("hwmon: add Corsair Commander Pro driver")
Signed-off-by: Marius Zachmann <mail@mariuszachmann.de>
Link: https://lore.kernel.org/r/20250619132817.39764-5-mail@mariuszachmann.de
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Author: MisterZ42

drivers/hwmon/corsair-cpro.c

@@ -89,6 +89,7 @@ struct ccp_device {
 	struct mutex mutex; /* whenever buffer is used, lock before send_usb_cmd */
 	u8 *cmd_buffer;
 	u8 *buffer;
+	int buffer_recv_size; /* number of received bytes in buffer */
 	int target[6];
 	DECLARE_BITMAP(temp_cnct, NUM_TEMP_SENSORS);
 	DECLARE_BITMAP(fan_cnct, NUM_FANS);
@@ -146,6 +147,9 @@ static int send_usb_cmd(struct ccp_device *ccp, u8 command, u8 byte1, u8 byte2,
 	if (!t)
 		return -ETIMEDOUT;
 
+	if (ccp->buffer_recv_size != IN_BUFFER_SIZE)
+		return -EPROTO;
+
 	return ccp_get_errno(ccp);
 }
 
@@ -157,6 +161,7 @@ static int ccp_raw_event(struct hid_device *hdev, struct hid_report *report, u8
 	spin_lock(&ccp->wait_input_report_lock);
 	if (!completion_done(&ccp->wait_input_report)) {
 		memcpy(ccp->buffer, data, min(IN_BUFFER_SIZE, size));
+		ccp->buffer_recv_size = size;
 		complete_all(&ccp->wait_input_report);
 	}
 	spin_unlock(&ccp->wait_input_report_lock);