Re: [PATCH net-next 5/5] sctp: add spt_pathcpthld in struct sctp_paddrthlds

[Xin Long]

On Wed, Sep 11, 2019 at 1:27 AM David Miller <da...@davemloft.net> wrote:
>
> From: Xin Long <lucien....@gmail.com>
> Date: Mon,  9 Sep 2019 15:56:51 +0800
>
> > diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
> > index a15cc28..dfd81e1 100644
> > --- a/include/uapi/linux/sctp.h
> > +++ b/include/uapi/linux/sctp.h
> > @@ -1069,6 +1069,7 @@ struct sctp_paddrthlds {
> >       struct sockaddr_storage spt_address;
> >       __u16 spt_pathmaxrxt;
> >       __u16 spt_pathpfthld;
> > +     __u16 spt_pathcpthld;
> >  };
> >
> >  /*
>
> As pointed out you can't add things to this structure without breaking 
> existing
> binaries.
we had the same problem when adding:
spp_ipv6_flowlabel and spp_dscp into struct sctp_paddrparams. in:

commit 0b0dce7a36fb9f1a9dd8245ea82d3a268c6943fe
Author: Xin Long <lucien....@gmail.com>
Date:   Mon Jul 2 18:21:13 2018 +0800

    sctp: add spp_ipv6_flowlabel and spp_dscp for sctp_paddrparams

the solution was:

        if (optlen == sizeof(params)) {
                if (copy_from_user(&params, optval, optlen))
                        return -EFAULT;
        } else if (optlen == ALIGN(offsetof(struct sctp_paddrparams,
                                            spp_ipv6_flowlabel), 4)) {
                if (copy_from_user(&params, optval, optlen))
                        return -EFAULT;
                if (params.spp_flags & (SPP_DSCP | SPP_IPV6_FLOWLABEL))
                        return -EINVAL;
        } else {
                return -EINVAL;
        }

I will do the same for this patch. Thanks.