Hi Stefan,

On 05/07/18 13:16, Stefan Schmidt wrote:
> Hello.
> 
> [CC David Palma and Rabi Narayan Sahoo]
> 
> On 02.07.2018 22:32, Alexander Aring wrote:
>> This patch fixes patch add handling to take care tail and headroom for
>> single 6lowpan frames. We need to be sure we have a skb with the right
>> head and tailroom for single frames. This patch do it by using
>> skb_copy_expand() if head and tailroom is not enough allocated by upper
>> layer.
>>
>> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=195059
>> Reported-by: David Palma <david.pa...@ntnu.no>
>> Reported-by: Rabi Narayan Sahoo <rabinarayans0...@gmail.com>
>> Signed-off-by: Alexander Aring <ar...@mojatatu.com>
> 
> David, Rabi and you please test these two patches and verify that it
> fixes the problems you have?
> 
> regards
> Stefan Schmidt
> 

The patches fix the problems!

I've tested them against different packet sizes and no kernel panic.

The patches were applied in Debian's 4.9.88-1+deb9u1 x86_64 kernel,
which before the patches showed the reported issue.

Thanks again to Alex for looking into it.

Cheers,
-- 
David

>> ---
>>  net/ieee802154/6lowpan/tx.c | 21 ++++++++++++++++++---
>>  1 file changed, 18 insertions(+), 3 deletions(-)
>>
>> diff --git a/net/ieee802154/6lowpan/tx.c b/net/ieee802154/6lowpan/tx.c
>> index e6ff5128e61a..d0c4d220de08 100644
>> --- a/net/ieee802154/6lowpan/tx.c
>> +++ b/net/ieee802154/6lowpan/tx.c
>> @@ -265,9 +265,24 @@ netdev_tx_t lowpan_xmit(struct sk_buff *skb, struct 
>> net_device *ldev)
>>      /* We must take a copy of the skb before we modify/replace the ipv6
>>       * header as the header could be used elsewhere
>>       */
>> -    skb = skb_unshare(skb, GFP_ATOMIC);
>> -    if (!skb)
>> -            return NET_XMIT_DROP;
>> +    if (unlikely(skb_headroom(skb) < ldev->needed_headroom ||
>> +                 skb_tailroom(skb) < ldev->needed_tailroom)) {
>> +            struct sk_buff *nskb;
>> +
>> +            nskb = skb_copy_expand(skb, ldev->needed_headroom,
>> +                                   ldev->needed_tailroom, GFP_ATOMIC);
>> +            if (likely(skb)) {
>> +                    consume_skb(skb);
>> +                    skb = nskb;
>> +            } else {
>> +                    kfree_skb(skb);
>> +                    return NET_XMIT_DROP;
>> +            }
>> +    } else {
>> +            skb = skb_unshare(skb, GFP_ATOMIC);
>> +            if (!skb)
>> +                    return NET_XMIT_DROP;
>> +    }
>>  
>>      ret = lowpan_header(skb, ldev, &dgram_size, &dgram_offset);
>>      if (ret < 0) {
>>


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