Re: [PATCH v4 bluetooth] Fix lowpan_rcv

[Martin Townsend <martin.townsend@xsilon.com>]

Hi Jukka,

Thanks for investigating this. 

If you set the dev in your receive function does the oops go away,  BTW this is where the pkt_type is set to PACKET_HOST, for us this was causing problems, I don't know if this is the same for you guys.

Here's the code:

            local_skb->protocol = htons(ETH_P_IPV6);
>>>     local_skb->dev = dev;
            local_skb->pkt_type = PACKET_HOST;

            if (give_skb_to_upper(local_skb, dev)
                            != NET_RX_SUCCESS) {
                kfree_skb(local_skb);

- Martin.

On 02/10/14 12:28, Jukka Rissanen wrote:
> Hi Martin,
>
> On ke, 2014-10-01 at 16:24 +0100, Martin Townsend wrote:
>> Hi Jukka,
>>
>> I spotted one thing in recv_pkt when skb_copy_expand fails it should goto drop but this is not what you are seeing.  This also exists in 6lowpan_rtnl.c so I will fix this in both for the next patch.
>>
>> I would be interested to know if the 802.15.4 wireless guys are seeing this to narrow this down.  I don't see this but then I had to manually add the code into my bluetooth tree from ours due to differences so I could have well screwed something up.
>>
>> - Martin.
>>
>> On 01/10/14 15:47, Jukka Rissanen wrote:
>>> Hi Martin,
>>>
>>> just in case add me to cc: next time so I do not miss these 6lowpan
>>> patches.
>>>
>>> On ke, 2014-10-01 at 13:10 +0100, Martin Townsend wrote:
>>>> This series aims to fix incorrect return values in lowpan_rcv
>>>> To achieve this it also refactors the receive path to
>>>>   1) free skb only from lowpan_rcv and not functions that it calls
>>>>   2) move skb delivery from IPHC
>>>>
>>>> I have only compile tested the changes for bluetooth as I don't have any HW
>>>> available so would be grateful for any testing from the Bluetooth developers.
>>>> I have done some minimal testing for IEEE802.15.4
>>> FYI, I tried this with latest bluetooth-next tree and got following oops
>>> when trying to connect to peer bt 6lowpan device. The system probably
>>> crashed before any packet was delivered to peer as I did not see
>>> anything on the other end of the connection.
>>>
>>>
>>> BUG: unable to handle kernel NULL pointer dereference at 000000a0
>>> IP: [<c17712c3>] __netif_receive_skb_core+0xa3/0x7b0
>>> *pde = 00000000 
>>> Oops: 0000 [#1] PREEMPT SMP 
>>> Modules linked in: bluetooth_6lowpan 6lowpan rfcomm bnep ecb btusb
>>> bluetooth nfc rfkill snd_intel8x0 ohci_pci snd_ac97_codec ac97_bus
>>> parport_pc parport
>>> CPU: 0 PID: 353 Comm: systemd-network Not tainted 3.17.0-rc1-bt6lowpan
>>> #1
>>> Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox
>>> 12/01/2006
>>> task: ccb695e0 ti: cc88e000 task.ti: cc88e000
>>> EIP: 0060:[<c17712c3>] EFLAGS: 00010282 CPU: 0
>>> EIP is at __netif_receive_skb_core+0xa3/0x7b0
>>> EAX: cd964900 EBX: cd964900 ECX: 00000000 EDX: 00000000
>>> ESI: cd964900 EDI: 00000001 EBP: cf00bf4c ESP: cf00bf18
>>>  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
>>> CR0: 8005003b CR2: d0cd6040 CR3: 0d057000 CR4: 000006d0
>>> Stack:
>>>  00000002 00000000 00000000 c1771279 cf73e698 cf00bf00 00000000 00000001
>>>  cd964900 00000046 cd964900 00000000 cf73e698 cf00bf5c c17719eb cd964900
>>>  00000000 cf00bf80 c177300f cf73e664 cf73e670 00000040 cf73e5d4 cf73e698
>>> Call Trace:
>>>  [<c1771279>] ? __netif_receive_skb_core+0x59/0x7b0
> I investigated this a bit more by adding some debug prints into
> __netif_receive_skb_core() and the reason for the oops is that the
> skb->dev is NULL.
>
> The culprit seems to be this removal from skb_deliver() function:
>
> -	new->dev = dev;
>
> And then dev is null in bluetooth side. You seem to set it in ieee802154
> side so the oops is not shown there.
>
>
>>>  [<c17719eb>] __netif_receive_skb+0x1b/0x70
>>>  [<c177300f>] process_backlog+0x9f/0x140
>>>  [<c1772e48>] net_rx_action+0x128/0x250
>>>  [<c104fd84>] __do_softirq+0xd4/0x300
>>>  [<c104fcb0>] ? __local_bh_enable_ip+0xf0/0xf0
>>>  [<c10049fc>] do_softirq_own_stack+0x2c/0x40
>>>  <IRQ> 
>>>  [<c1050136>] irq_exit+0x86/0xb0
>>>  [<c188bd98>] smp_apic_timer_interrupt+0x38/0x50
>>>  [<c188b6ce>] apic_timer_interrupt+0x32/0x38
>>> Code: 00 31 c9 c7 44 24 04 00 00 00 00 c7 04 24 02 00 00 00 31 d2 b8 14
>>> 42 c0 c1 e8 0a 1f 92 ff c7 45 e8 01 00 00 00 8b 45 ec 8b 50 14 <8b> 92
>>> a0 00 00 00 89 50 74 b8 f8 7c ad c1 e8 1a f7 c5 ff 8b 5d
>>> EIP: [<c17712c3>] __netif_receive_skb_core+0xa3/0x7b0 SS:ESP
>>> 0068:cf00bf18
>>> CR2: 00000000000000a0
>>> ---[ end trace 704a740b1671072d ]---
>>> Kernel panic - not syncing: Fatal exception in interrupt
>>> Kernel Offset: 0x0 from 0xc1000000 (relocation range:
>>> 0xc0000000-0xd07effff)
>>> ---[ end Kernel panic - not syncing: Fatal exception in interrupt
>>>
>>>
>>>
> Cheers,
> Jukka
>
>
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