netdev - Re: [net] tcp: Explicitly mark reserved field in tcp_zerocopy

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Date:   Fri, 5 Feb 2021 22:59:29 -0800
From:   Arjun Roy <arjunroy@...gle.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Arjun Roy <arjunroy.kdev@...il.com>,
        David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Leon Romanovsky <leon@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [net] tcp: Explicitly mark reserved field in tcp_zerocopy_receive args.

On Fri, Feb 5, 2021 at 10:57 PM David Ahern <dsahern@...il.com> wrote:
>
> On 2/5/21 4:01 PM, Arjun Roy wrote:
> > From: Arjun Roy <arjunroy@...gle.com>
> >
> > Explicitly define reserved field and require it to be 0-valued.
> >
> > Fixes: 7eeba1706eba ("tcp: Add receive timestamp support for receive zerocopy.")
> > Signed-off-by: Arjun Roy <arjunroy@...gle.com>
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>
> > Suggested-by: David Ahern <dsahern@...il.com>
> > Suggested-by: Leon Romanovsky <leon@...nel.org>
> > Suggested-by: Jakub Kicinski <kuba@...nel.org>
> > ---
> >  include/uapi/linux/tcp.h | 2 +-
> >  net/ipv4/tcp.c           | 2 ++
> >  2 files changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
> > index 42fc5a640df4..8fc09e8638b3 100644
> > --- a/include/uapi/linux/tcp.h
> > +++ b/include/uapi/linux/tcp.h
> > @@ -357,6 +357,6 @@ struct tcp_zerocopy_receive {
> >       __u64 msg_control; /* ancillary data */
> >       __u64 msg_controllen;
> >       __u32 msg_flags;
> > -     /* __u32 hole;  Next we must add >1 u32 otherwise length checks fail. */
> > +     __u32 reserved; /* set to 0 for now */
> >  };
> >  #endif /* _UAPI_LINUX_TCP_H */
> > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> > index e1a17c6b473c..97aee57ab9b4 100644
> > --- a/net/ipv4/tcp.c
> > +++ b/net/ipv4/tcp.c
> > @@ -4159,6 +4159,8 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
> >               }
> >               if (copy_from_user(&zc, optval, len))
> >                       return -EFAULT;
> > +             if (zc.reserved)
> > +                     return -EOPNOTSUPP;
>
> usually invalid values for uapi return -EINVAL

I'll send out a v2 with that changed then.

-Arjun