netdev - Re: [Patch bpf-next v2 2/9] sock: introduce sk_prot->update

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Message-ID: <CAM_iQpXXUv1FV8DQ85a2fs08JCfKHHt-fAWYbV0TTWmwUZ-K5Q@mail.gmail.com>
Date:   Thu, 4 Mar 2021 15:52:03 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Lorenz Bauer <lmb@...udflare.com>
Cc:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        duanxiongchun@...edance.com,
        Dongdong Wang <wangdongdong.6@...edance.com>,
        Jiang Wang <jiang.wang@...edance.com>,
        Cong Wang <cong.wang@...edance.com>,
        John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Sitnicki <jakub@...udflare.com>
Subject: Re: [Patch bpf-next v2 2/9] sock: introduce sk_prot->update_proto()

On Tue, Mar 2, 2021 at 10:23 AM Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> On Tue, Mar 2, 2021 at 8:22 AM Lorenz Bauer <lmb@...udflare.com> wrote:
> >
> > On Tue, 2 Mar 2021 at 02:37, Cong Wang <xiyou.wangcong@...il.com> wrote:
> >
> > ...
> > >  static inline void sk_psock_restore_proto(struct sock *sk,
> > >                                           struct sk_psock *psock)
> > >  {
> > >         sk->sk_prot->unhash = psock->saved_unhash;
> >
> > Not related to your patch set, but why do an extra restore of
> > sk_prot->unhash here? At this point sk->sk_prot is one of our tcp_bpf
> > / udp_bpf protos, so overwriting that seems wrong?
>
> Good catch. It seems you are right, but I need a double check. And
> yes, it is completely unrelated to my patch, as the current code has
> the same problem.

Looking at this again. I noticed

commit 4da6a196f93b1af7612340e8c1ad8ce71e18f955
Author: John Fastabend <john.fastabend@...il.com>
Date:   Sat Jan 11 06:11:59 2020 +0000

    bpf: Sockmap/tls, during free we may call tcp_bpf_unhash() in loop

intentionally fixed a bug in kTLS with overwriting this ->unhash.

I agree with you that it should not be updated for sockmap case,
however I don't know what to do with kTLS case, it seems the bug the
above commit fixed still exists if we just revert it.

Anyway, this should be targeted for -bpf as a bug fix, so it does not
belong to this patchset.

Thanks.