Re: [Intel-wired-lan] [PATCH net/jkirsher] bpf, xdp, i40e: fix i40e_build_skb skb reserve and truesize

[Alexander Duyck <alexander.duyck@gmail.com>]

On Wed, Jun 13, 2018 at 9:26 AM, John Fastabend
<john.fastabend@gmail.com> wrote:
> On 06/13/2018 02:04 AM, Daniel Borkmann wrote:
>> Using skb_reserve(skb, I40E_SKB_PAD + (xdp->data - xdp->data_hard_start))
>> is clearly wrong since I40E_SKB_PAD already points to the offset where
>> the original xdp->data was sitting since xdp->data_hard_start is defined
>> as xdp->data - i40e_rx_offset(rx_ring) where latter offsets to I40E_SKB_PAD
>> when build skb is used.
>>
>> However, also before cc5b114dcf98 ("bpf, i40e: add meta data support")
>> this seems broken since bpf_xdp_adjust_head() helper could have been used
>> to alter headroom and enlarge / shrink the frame and with that the assumption
>> that the xdp->data remains unchanged does not hold and would push a bogus
>> packet to upper stack.
>>
>> ixgbe got this right in 924708081629 ("ixgbe: add XDP support for pass and
>> drop actions"). In any case, fix it by removing the I40E_SKB_PAD from both
>> skb_reserve() and truesize calculation.
>>
>> Fixes: cc5b114dcf98 ("bpf, i40e: add meta data support")
>> Fixes: 0c8493d90b6b ("i40e: add XDP support for pass and drop actions")
>> Reported-by: Keith Busch <keith.busch@linux.intel.com>
>> Reported-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
>> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
>> Cc: Björn Töpel <bjorn.topel@intel.com>
>> Cc: John Fastabend <john.fastabend@gmail.com>
>> ---
>>  drivers/net/ethernet/intel/i40e/i40e_txrx.c | 7 +++----
>>  1 file changed, 3 insertions(+), 4 deletions(-)
>>
>
> Thanks! I missed this during review.
>
> Acked-by: John Fastabend <john.fastabend@gmail.com>

Looks good to me. Thanks for taking care of this.

Acked-by: Alexander Duyck <alexander.h.duyck@intel.com>