nfc: Ensure presence of required attributes in the deactivate_target handler

Check that the NFC_ATTR_TARGET_INDEX attributes (in addition to
NFC_ATTR_DEVICE_INDEX) are provided by the netlink client prior to
accessing them. This prevents potential unhandled NULL pointer dereference
exceptions which can be triggered by malicious user-mode programs,
if they omit one or both of these attributes.

Signed-off-by: Young Xiao <92siuyang@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
static int nfc_genl_deactivate_target(struct sk_buff *skb,
				      struct genl_info *info)
{
	struct nfc_dev *dev;
 	u32 device_idx, target_idx;
 	int rc;
 
	if (!info->attrs[NFC_ATTR_DEVICE_INDEX] ||
	    !info->attrs[NFC_ATTR_TARGET_INDEX])
 		return -EINVAL;
 
 	device_idx = nla_get_u32(info->attrs[NFC_ATTR_DEVICE_INDEX]);

	dev = nfc_get_device(device_idx);
	if (!dev)
		return -ENODEV;

	target_idx = nla_get_u32(info->attrs[NFC_ATTR_TARGET_INDEX]);

	rc = nfc_deactivate_target(dev, target_idx, NFC_TARGET_MODE_SLEEP);

	nfc_put_device(dev);
	return rc;
}

static int nfc_genl_deactivate_target(struct sk_buff *skb,
				      struct genl_info *info)
{
	struct nfc_dev *dev;
 	u32 device_idx, target_idx;
 	int rc;
 
	if (!info->attrs[NFC_ATTR_DEVICE_INDEX])
 		return -EINVAL;
 
 	device_idx = nla_get_u32(info->attrs[NFC_ATTR_DEVICE_INDEX]);

	dev = nfc_get_device(device_idx);
	if (!dev)
		return -ENODEV;

	target_idx = nla_get_u32(info->attrs[NFC_ATTR_TARGET_INDEX]);

	rc = nfc_deactivate_target(dev, target_idx, NFC_TARGET_MODE_SLEEP);

	nfc_put_device(dev);
	return rc;
}
