mac802154: fix missing INIT_LIST_HEAD in ieee802154_if_add()

Kernel fault injection test reports null-ptr-deref as follows:

BUG: kernel NULL pointer dereference, address: 0000000000000008
RIP: 0010:cfg802154_netdev_notifier_call+0x120/0x310 include/linux/list.h:114
Call Trace:
 <TASK>
 raw_notifier_call_chain+0x6d/0xa0 kernel/notifier.c:87
 call_netdevice_notifiers_info+0x6e/0xc0 net/core/dev.c:1944
 unregister_netdevice_many_notify+0x60d/0xcb0 net/core/dev.c:1982
 unregister_netdevice_queue+0x154/0x1a0 net/core/dev.c:10879
 register_netdevice+0x9a8/0xb90 net/core/dev.c:10083
 ieee802154_if_add+0x6ed/0x7e0 net/mac802154/iface.c:659
 ieee802154_register_hw+0x29c/0x330 net/mac802154/main.c:229
 mcr20a_probe+0xaaa/0xcb1 drivers/net/ieee802154/mcr20a.c:1316

ieee802154_if_add() allocates wpan_dev as netdev's private data, but not
init the list in struct wpan_dev. cfg802154_netdev_notifier_call() manage
the list when device register/unregister, and may lead to null-ptr-deref.

Use INIT_LIST_HEAD() on it to initialize it correctly.

Fixes: fcf39e6 ("ieee802154: add wpan_dev_list")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Alexander Aring <aahringo@redhat.com>

Link: https://lore.kernel.org/r/20221130091705.1831140-1-weiyongjun@huaweicloud.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

Author: Wei Yongjun

net/mac802154/iface.c

@@ -662,6 +662,7 @@ ieee802154_if_add(struct ieee802154_local *local, const char *name,
 	sdata->dev = ndev;
 	sdata->wpan_dev.wpan_phy = local->hw.phy;
 	sdata->local = local;
+	INIT_LIST_HEAD(&sdata->wpan_dev.list);
 
 	/* setup type-dependent data */
 	ret = ieee802154_setup_sdata(sdata, type);