[ETHTOOL]: Add support for large eeproms

Currently, it is not possible to read/write to an eeprom larger than
128k in size because the buffer used for temporarily storing the
eeprom contents is allocated using kmalloc. kmalloc can only allocate
a maximum of 128k depending on architecture.

Modified ethtool_get/set_eeprom to only allocate a page of memory and
then copy the eeprom a page at a time.

Updated original patch as per suggestions from Joe Perches.
Signed-off-by: Mandeep Singh Baines <msb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/ethtool.c

@@ -284,8 +284,10 @@ static int ethtool_get_eeprom(struct net_device *dev, void __user *useraddr)
 {
 	struct ethtool_eeprom eeprom;
 	const struct ethtool_ops *ops = dev->ethtool_ops;
+	void __user *userbuf = useraddr + sizeof(eeprom);
+	u32 bytes_remaining;
 	u8 *data;
-	int ret;
+	int ret = 0;
 
 	if (!ops->get_eeprom || !ops->get_eeprom_len)
 		return -EOPNOTSUPP;
@@ -301,26 +303,26 @@ static int ethtool_get_eeprom(struct net_device *dev, void __user *useraddr)
 	if (eeprom.offset + eeprom.len > ops->get_eeprom_len(dev))
 		return -EINVAL;
 
-	data = kmalloc(eeprom.len, GFP_USER);
+	data = kmalloc(PAGE_SIZE, GFP_USER);
 	if (!data)
 		return -ENOMEM;
 
-	ret = -EFAULT;
-	if (copy_from_user(data, useraddr + sizeof(eeprom), eeprom.len))
-		goto out;
+	bytes_remaining = eeprom.len;
+	while (bytes_remaining > 0) {
+		eeprom.len = min(bytes_remaining, (u32)PAGE_SIZE);
 
 		ret = ops->get_eeprom(dev, &eeprom, data);
 		if (ret)
-		goto out;
-
+			break;
+		if (copy_to_user(userbuf, data, eeprom.len)) {
 			ret = -EFAULT;
-	if (copy_to_user(useraddr, &eeprom, sizeof(eeprom)))
-		goto out;
-	if (copy_to_user(useraddr + sizeof(eeprom), data, eeprom.len))
-		goto out;
-	ret = 0;
+			break;
+		}
+		userbuf += eeprom.len;
+		eeprom.offset += eeprom.len;
+		bytes_remaining -= eeprom.len;
+	}
 
- out:
 	kfree(data);
 	return ret;
 }
@@ -329,8 +331,10 @@ static int ethtool_set_eeprom(struct net_device *dev, void __user *useraddr)
 {
 	struct ethtool_eeprom eeprom;
 	const struct ethtool_ops *ops = dev->ethtool_ops;
+	void __user *userbuf = useraddr + sizeof(eeprom);
+	u32 bytes_remaining;
 	u8 *data;
-	int ret;
+	int ret = 0;
 
 	if (!ops->set_eeprom || !ops->get_eeprom_len)
 		return -EOPNOTSUPP;
@@ -346,22 +350,26 @@ static int ethtool_set_eeprom(struct net_device *dev, void __user *useraddr)
 	if (eeprom.offset + eeprom.len > ops->get_eeprom_len(dev))
 		return -EINVAL;
 
-	data = kmalloc(eeprom.len, GFP_USER);
+	data = kmalloc(PAGE_SIZE, GFP_USER);
 	if (!data)
 		return -ENOMEM;
 
-	ret = -EFAULT;
-	if (copy_from_user(data, useraddr + sizeof(eeprom), eeprom.len))
-		goto out;
+	bytes_remaining = eeprom.len;
+	while (bytes_remaining > 0) {
+		eeprom.len = min(bytes_remaining, (u32)PAGE_SIZE);
 
+		if (copy_from_user(data, userbuf, eeprom.len)) {
+			ret = -EFAULT;
+			break;
+		}
 		ret = ops->set_eeprom(dev, &eeprom, data);
 		if (ret)
-		goto out;
-
-	if (copy_to_user(useraddr + sizeof(eeprom), data, eeprom.len))
-		ret = -EFAULT;
+			break;
+		userbuf += eeprom.len;
+		eeprom.offset += eeprom.len;
+		bytes_remaining -= eeprom.len;
+	}
 
- out:
 	kfree(data);
 	return ret;
 }