[PATCH 4.9 07/28] ieee802154: 6lowpan: fix possible NULL deref in lowpan_device_event()

Greg Kroah-Hartman
2018-03-29T18:00:26Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit ca0edb131bdf1e6beaeb2b8289fd6b374b74147d ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ieee802154/6lowpan/core.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

--- a/net/ieee802154/6lowpan/core.c
+++ b/net/ieee802154/6lowpan/core.c
@@ -204,9 +204,13 @@ static inline void lowpan_netlink_fini(v
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) {
@@ -215,8 +219,8 @@ static int lowpan_device_event(struct no
* 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;