Re: [PATCH] net: add missing skb_uarg refcount increment in pskb_carve_inside_header()

[linmiaohe]

Willem de Bruijn <willemdebruijn.kernel@xxxxxxxxx> wrote:
>On Thu, Aug 13, 2020 at 2:16 PM Miaohe Lin <linmiaohe@xxxxxxxxxx> wrote:
>>
>> If the skb is zcopied, we should increase the skb_uarg refcount before 
>> we involve skb_release_data(). See pskb_expand_head() as a reference.
>
>Did you manage to observe a bug through this datapath in practice?
>
>pskb_carve_inside_header is called
>  from pskb_carve
>    from pskb_extract
>      from rds_tcp_data_recv
>
>That receive path should not see any packets with zerocopy state associated.
>

This works fine yet as its caller is limited. But we should take care of the skb_uarg refcount for future use.
On the other hand, because this codepath should not see any packets with zerocopy state associated, then we
should not call skb_orphan_frags here.

Thanks.

>> Fixes: 6fa01ccd8830 ("skbuff: Add pskb_extract() helper function")
>> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>