i2c/eeprom: Recognize VGN as a valid Sony Vaio name prefix

patch 8b925a3d in mainline.

Recent (i.e. 2005 and later) Sony Vaio laptops have names beginning
with VGN rather than PCG. Update the eeprom driver so that it
recognizes these.

Why this matters: the eeprom driver hides private data from the
EEPROMs it recognizes as Vaio EEPROMs (passwords, serial number...) so
if the driver fails to recognize a Vaio EEPROM as such, the private
data is exposed to the world.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/i2c/chips/eeprom.c

@@ -197,12 +197,16 @@ static int eeprom_detect(struct i2c_adapter *adapter, int address, int kind)
 		goto exit_kfree;
 
 	/* Detect the Vaio nature of EEPROMs.
-	   We use the "PCG-" prefix as the signature. */
+	   We use the "PCG-" or "VGN-" prefix as the signature. */
 	if (address == 0x57) {
-		if (i2c_smbus_read_byte_data(new_client, 0x80) == 'P'
-		 && i2c_smbus_read_byte(new_client) == 'C'
-		 && i2c_smbus_read_byte(new_client) == 'G'
-		 && i2c_smbus_read_byte(new_client) == '-') {
+		char name[4];
+
+		name[0] = i2c_smbus_read_byte_data(new_client, 0x80);
+		name[1] = i2c_smbus_read_byte(new_client);
+		name[2] = i2c_smbus_read_byte(new_client);
+		name[3] = i2c_smbus_read_byte(new_client);
+
+		if (!memcmp(name, "PCG-", 4) || !memcmp(name, "VGN-", 4)) {
 			dev_info(&new_client->dev, "Vaio EEPROM detected, "
 				"enabling password protection\n");
 			data->nature = VAIO;