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: 2c88b52 ("ieee802154: 6lowpan: remove check on null") Signed-off-by: Eric Dumazet <[email protected]> Cc: Alexander Aring <[email protected]> Cc: Stefan Schmidt <[email protected]> Reported-by: syzbot <[email protected]> Acked-by: Stefan Schmidt <[email protected]> Signed-off-by: David S. Miller <[email protected]>
jbg · Mar 9, 2018 · ca0edb1 · ca0edb1
1 parent 9f62c15
commit ca0edb1
Showing 1 changed file with 8 additions and 4 deletions.
diff --git 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;