ieee802154: 6lowpan: fix possible NULL deref in lowpan_device_event()

A tun device type can trivially be set to arbitrary value using
TUNSETLINK ioctl().

Therefore, lowpan_device_event() must really check that ieee802154_ptr
is not NULL.

Fixes: 2c88b5283f60d ("ieee802154: 6lowpan: remove check on null")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Alexander Aring <alex.aring@gmail.com>
Cc: Stefan Schmidt <stefan@osg.samsung.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Acked-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ieee802154/6lowpan/core.c b/net/ieee802154/6lowpan/core.c
index 974765b7d92a75546fe5ae5dbc332078a54f627a..e9f0489e422944ee15b40e10e39bc7200c4bb905 100644 (file)
--- a/net/ieee802154/6lowpan/core.c
+++ b/net/ieee802154/6lowpan/core.c
@@ -206,9 +206,13 @@ static inline void lowpan_netlink_fini(void)
 static int lowpan_device_event(struct notifier_block *unused,
                               unsigned long event, void *ptr)
 {
-       struct net_device *wdev = netdev_notifier_info_to_dev(ptr);
+       struct net_device *ndev = netdev_notifier_info_to_dev(ptr);
+       struct wpan_dev *wpan_dev;
 
-       if (wdev->type != ARPHRD_IEEE802154)
+       if (ndev->type != ARPHRD_IEEE802154)
+               return NOTIFY_DONE;
+       wpan_dev = ndev->ieee802154_ptr;
+       if (!wpan_dev)
                return NOTIFY_DONE;
 
        switch (event) {
@@ -217,8 +221,8 @@ static int lowpan_device_event(struct notifier_block *unused,
                 * also delete possible lowpan interfaces which belongs
                 * to the wpan interface.
                 */
-               if (wdev->ieee802154_ptr->lowpan_dev)
-                       lowpan_dellink(wdev->ieee802154_ptr->lowpan_dev, NULL);
+               if (wpan_dev->lowpan_dev)
+                       lowpan_dellink(wpan_dev->lowpan_dev, NULL);
                break;
        default:
                return NOTIFY_DONE;