netdev - Re: [Patch net v3] cls_flower: call nla_ok() before nla

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Message-ID: <CAM_iQpVAer0tBocMXGa0G_8jqJVz5oJ--woPo+TrtzVemyz+rQ@mail.gmail.com>
Date:   Thu, 14 Jan 2021 13:57:13 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Cong Wang <cong.wang@...edance.com>,
        syzbot <syzbot+2624e3778b18fc497c92@...kaller.appspotmail.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Xin Long <lucien.xin@...il.com>, Jiri Pirko <jiri@...nulli.us>
Subject: Re: [Patch net v3] cls_flower: call nla_ok() before nla_next()

On Thu, Jan 14, 2021 at 1:36 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Thu, 14 Jan 2021 13:07:49 -0800 Cong Wang wrote:
> > -                     if (msk_depth)
> > -                             nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
> >                       break;
> >               default:
> >                       NL_SET_ERR_MSG(extack, "Unknown tunnel option type");
> >                       return -EINVAL;
> >               }
> > +
> > +             if (!nla_opt_msk)
> > +                     continue;
>
> Why the switch from !msk_depth to !nla_opt_msk?

It is the same, when nla_opt_msk is NULL, msk_depth is 0.
Checking nla_opt_msk is NULL is more readable to express that
mask is not provided.

>
> Seems like previously providing masks for only subset of options
> would have worked.

I don't think so, every type has this check:

                        if (key->enc_opts.len != mask->enc_opts.len) {
                                NL_SET_ERR_MSG(extack, "Key and mask
miss aligned");
                                return -EINVAL;
                        }

which guarantees the numbers are aligned.

Thanks.