[PATCH net] ieee802154: 6lowpan: fix possible NULL deref in lowpan_device_event()

From: Eric Dumazet <redacted>

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 <redacted>
Cc: Alexander Aring <alex.aring@gmail.com>
Cc: Stefan Schmidt <redacted>
Reported-by: syzbot <redacted>
---
 net/ieee802154/6lowpan/core.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/ieee802154/6lowpan/core.c b/net/ieee802154/6lowpan/core.c
index 974765b7d92a..e9f0489e4229 100644
--- 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;

From: Eric Dumazet <redacted>
Date: Mon, 05 Mar 2018 08:51:03 -0800

From: Eric Dumazet <redacted>

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 <redacted>
Cc: Alexander Aring <alex.aring@gmail.com>
Cc: Stefan Schmidt <redacted>
Reported-by: syzbot <redacted>

Adding linux-wpan list.

Hello.


On 03/05/2018 05:51 PM, Eric Dumazet wrote:

Not sure why you think there is a rename from wdev to ndev necessary.
I see this more of a rolled in cosmetic change, but its not a real problem from my side.

Thanks a lot for fixing this and syzbot for finding it.


Acked-by: Stefan Schmidt <redacted>

Dave, could you take this one directly? I have no other patches pending for your net tree (only net-next) and having a pull request for just
this patch does not make much sense.

regards
Stefan Schmidt

Hello Dave.


On 03/06/2018 01:56 PM, Stefan Schmidt wrote:

Hello.


On 03/05/2018 05:51 PM, Eric Dumazet wrote:

quoted

From: Eric Dumazet <redacted>

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 <redacted>
Cc: Alexander Aring <alex.aring@gmail.com>
Cc: Stefan Schmidt <redacted>
Reported-by: syzbot <redacted>
---
 net/ieee802154/6lowpan/core.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/ieee802154/6lowpan/core.c b/net/ieee802154/6lowpan/core.c
index 974765b7d92a..e9f0489e4229 100644
--- 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);

Not sure why you think there is a rename from wdev to ndev necessary.
I see this more of a rolled in cosmetic change, but its not a real problem from my side.

quoted

+	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;

Thanks a lot for fixing this and syzbot for finding it.


Acked-by: Stefan Schmidt <redacted>

Dave, could you take this one directly? I have no other patches pending for your net tree (only net-next) and having a pull request for just
this patch does not make much sense.

Did you miss this or would you prefer if I do a pull request for this single patch?
Either way would be fine with me.

regards
Stefan Schmidt

From: Stefan Schmidt <redacted>
Date: Thu, 8 Mar 2018 17:21:49 +0100

Did you miss this or would you prefer if I do a pull request for
this single patch?  Either way would be fine with me.

Sorry, this escaped me.

Applied and queued up for -stable, thanks.