linux-kernel - Re: [PATCH] net: add missing skb_uarg refcount increment in pskb_carve_inside

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Message-ID: <CA+FuTSeS9eE_1bsik-0i3qb-WXtQnb3q=mo6+iHOciQjLZ+sHQ@mail.gmail.com>
Date:   Thu, 13 Aug 2020 14:50:22 +0200
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Florian Westphal <fw@...len.de>, martin.varghese@...ia.com,
        pshelar@....org, dcaratti@...hat.com,
        Eric Dumazet <edumazet@...gle.com>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Shmulik Ladkani <shmulik@...anetworks.com>,
        Yadu Kishore <kyk.segfault@...il.com>,
        sowmini.varadhan@...cle.com,
        Network Development <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: add missing skb_uarg refcount increment in pskb_carve_inside_header()

On Thu, Aug 13, 2020 at 2:16 PM Miaohe Lin <linmiaohe@...wei.com> 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.


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