netdev - Re: [PATCH net] sctp: annotate data-races around sk->sk_wmem

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Message-ID: <CADvbK_d07SQ=xO=GtGL8DzOQH2x=T2ObMWdUknQrTnQT+-JZLw@mail.gmail.com>
Date: Tue, 29 Aug 2023 15:44:48 -0400
From: Xin Long <lucien.xin@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, syzbot <syzkaller@...glegroups.com>, 
	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Subject: Re: [PATCH net] sctp: annotate data-races around sk->sk_wmem_queued

On Tue, Aug 29, 2023 at 3:24 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Tue, Aug 29, 2023 at 9:05 PM Xin Long <lucien.xin@...il.com> wrote:
> >
> > On Tue, Aug 29, 2023 at 2:19 PM Eric Dumazet <edumazet@...gle.com> wrote:
> > >
> > > On Tue, Aug 29, 2023 at 8:14 PM Xin Long <lucien.xin@...il.com> wrote:
> > > >
> > > > On Mon, Aug 28, 2023 at 8:44 AM Eric Dumazet <edumazet@...gle.com> wrote:
> > > > >
> > > > > sk->sk_wmem_queued can be read locklessly from sctp_poll()
> > > > >
> > > > >                 sk->sk_rcvbuf);
> > > > Just wondering why sk->sk_sndbuf/sk_rcvbuf doesn't need READ_ONCE()
> > > > while adding READ_ONCE for sk->sk_wmem_queued in here?
> > > >
> > >
> > > Separate patches for sk_sndbuf, sk_rcvbuf, sk_err, sk_shutdown, and
> > > many other socket fields.
> > >
> > > I prefer having small patches to reduce merge conflicts in backports.
> > >
> > > Note that I used  READ_ONCE(sk->sk_sndbuf) in sctp_writeable(),
> > > (I assume this is why you asked)
> > Yes.
> >
> > Not sure about tcp's seq_show, but as sctp_assocs_seq_show() is only
>
> tcp seq_show uses requested spinlocks on lhash or ehash tables, but
> not socket lock.
>
> > under rcu_read_lock() and with a hold of transport/association/socket,
> > does it mean all members of assoc should also use READ_ONCE()?
>
> Probably...
OK, just thinking syzbot may report it in the future here.

>
> > (Note I think we don't expect the seq show to be that accurate.)
>
> Yeah, this is really best effort, inet_diag is probably what we want
> to harden these days.

Acked-by: Xin Long <lucien.xin@...il.com>

Thanks.