net: ieee802154: fix nl802154 del llsec devkey

commit 27c7468 upstream.

This patch fixes a nullpointer dereference if NL802154_ATTR_SEC_DEVKEY is
not set by the user. If this is the case nl802154 will return -EINVAL.

Reported-by: syzbot+368672e0da240db53b5f@syzkaller.appspotmail.com
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20210221174321.14210-4-aahringo@redhat.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/ieee802154/nl802154.c

@@ -1908,7 +1908,8 @@ static int nl802154_del_llsec_devkey(struct sk_buff *skb, struct genl_info *info
 	struct ieee802154_llsec_device_key key;
 	__le64 extended_addr;
 
-	if (nla_parse_nested(attrs, NL802154_DEVKEY_ATTR_MAX,
+	if (!info->attrs[NL802154_ATTR_SEC_DEVKEY] ||
+	    nla_parse_nested(attrs, NL802154_DEVKEY_ATTR_MAX,
 			     info->attrs[NL802154_ATTR_SEC_DEVKEY],
 			     nl802154_devkey_policy))
 		return -EINVAL;