Code: 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;
}

Vulnerability Type: DoS 
CWE ID: CWE-476
Summary: A NULL pointer dereference vulnerability in the function nfc_genl_deactivate_target() in net/nfc/netlink.c in the Linux kernel before 5.1.13 can be triggered by a malicious user-mode program that omits certain NFC attributes, leading to denial of service.
Commit Message: 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>