netdev - Re: [PATCH net] ieee802154: 6lowpan: fix possible NULL deref in lowpan_device

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Date:   Thu, 8 Mar 2018 17:21:49 +0100
From:   Stefan Schmidt <stefan@....samsung.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Alexander Aring <alex.aring@...il.com>,
        linux-wpan@...r.kernel.org
Subject: Re: [PATCH net] ieee802154: 6lowpan: fix possible NULL deref in
 lowpan_device_event()

Hello Dave.


On 03/06/2018 01:56 PM, Stefan Schmidt wrote:
> Hello.
>
>
> On 03/05/2018 05:51 PM, Eric Dumazet wrote:
>> From: Eric Dumazet <edumazet@...gle.com>
>>
>> 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@...gle.com>
>> Cc: Alexander Aring <alex.aring@...il.com>
>> Cc: Stefan Schmidt <stefan@....samsung.com>
>> Reported-by: syzbot <syzkaller@...glegroups.com>
>> ---
>>  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.
>
>> +	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 <stefan@....samsung.com>
>
> 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