net: ieee802154: fix nl802154 del llsec dev

This patch fixes a nullpointer dereference if NL802154_ATTR_SEC_DEVICE is
not set by the user. If this is the case nl802154 will return -EINVAL.

Reported-by: syzbot+d946223c2e751d136c94@syzkaller.appspotmail.com
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20210221174321.14210-2-aahringo@redhat.comSigned-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

net/ieee802154/nl802154.c

@@ -1758,7 +1758,8 @@ static int nl802154_del_llsec_dev(struct sk_buff *skb, struct genl_info *info)
 	struct nlattr *attrs[NL802154_DEV_ATTR_MAX + 1];
 	__le64 extended_addr;
 
-	if (nla_parse_nested_deprecated(attrs, NL802154_DEV_ATTR_MAX, info->attrs[NL802154_ATTR_SEC_DEVICE], nl802154_dev_policy, info->extack))
+	if (!info->attrs[NL802154_ATTR_SEC_DEVICE] ||
+	    nla_parse_nested_deprecated(attrs, NL802154_DEV_ATTR_MAX, info->attrs[NL802154_ATTR_SEC_DEVICE], nl802154_dev_policy, info->extack))
 		return -EINVAL;
 
 	if (!attrs[NL802154_DEV_ATTR_EXTENDED_ADDR])