netdev - Re: [PATCH v1 net 2/2] fou: Don't allow 0 for FOU_ATTR

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Message-ID: <CAAVpQUD9um80LD36osX4SuFk0BmkViHsPbKnFFXy=KtYoT_Z6g@mail.gmail.com>
Date: Tue, 13 Jan 2026 23:15:42 -0800
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: "David S . Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>, 
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Tom Herbert <therbert@...gle.com>, Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v1 net 2/2] fou: Don't allow 0 for FOU_ATTR_IPPROTO.

On Tue, Jan 13, 2026 at 7:11 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Mon, 12 Jan 2026 20:06:36 +0000 Kuniyuki Iwashima wrote:
> > fou_udp_recv() has the same problem mentioned in the previous
> > patch.
> >
> > If FOU_ATTR_IPPROTO is set to 0, skb is not freed by
> > fou_udp_recv() nor "resubmit"-ted in ip_protocol_deliver_rcu().
> >
> > Let's forbid 0 for FOU_ATTR_IPPROTO.
> >
> > Fixes: 23461551c0062 ("fou: Support for foo-over-udp RX path")
> > Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
> > ---
> >  net/ipv4/fou_nl.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/net/ipv4/fou_nl.c b/net/ipv4/fou_nl.c
> > index 7a99639204b16..0dec9da1bff46 100644
> > --- a/net/ipv4/fou_nl.c
> > +++ b/net/ipv4/fou_nl.c
> > @@ -15,7 +15,7 @@
> >  const struct nla_policy fou_nl_policy[FOU_ATTR_IFINDEX + 1] = {
> >       [FOU_ATTR_PORT] = { .type = NLA_BE16, },
> >       [FOU_ATTR_AF] = { .type = NLA_U8, },
> > -     [FOU_ATTR_IPPROTO] = { .type = NLA_U8, },
> > +     [FOU_ATTR_IPPROTO] = { .type = NLA_U8, .min = 1 },
> >       [FOU_ATTR_TYPE] = { .type = NLA_U8, },
> >       [FOU_ATTR_REMCSUM_NOPARTIAL] = { .type = NLA_FLAG, },
> >       [FOU_ATTR_LOCAL_V4] = { .type = NLA_U32, },
>
> This code is generated, please use :
>
> diff --git a/Documentation/netlink/specs/fou.yaml b/Documentation/netlink/specs/fou.yaml
> index 8e7974ec453f..331f1b342b3a 100644
> --- a/Documentation/netlink/specs/fou.yaml
> +++ b/Documentation/netlink/specs/fou.yaml
> @@ -39,6 +39,8 @@ kernel-policy: global
>        -
>          name: ipproto
>          type: u8
> +        checks:
> +          min: 1
>        -
>          name: type
>          type: u8
> diff --git a/net/ipv4/fou_nl.c b/net/ipv4/fou_nl.c
> index 7a99639204b1..309d5ba983d0 100644
> --- a/net/ipv4/fou_nl.c
> +++ b/net/ipv4/fou_nl.c
> @@ -15,7 +15,7 @@
>  const struct nla_policy fou_nl_policy[FOU_ATTR_IFINDEX + 1] = {
>         [FOU_ATTR_PORT] = { .type = NLA_BE16, },
>         [FOU_ATTR_AF] = { .type = NLA_U8, },
> -       [FOU_ATTR_IPPROTO] = { .type = NLA_U8, },
> +       [FOU_ATTR_IPPROTO] = NLA_POLICY_MIN(NLA_U8, 1),
>         [FOU_ATTR_TYPE] = { .type = NLA_U8, },
>         [FOU_ATTR_REMCSUM_NOPARTIAL] = { .type = NLA_FLAG, },
>         [FOU_ATTR_LOCAL_V4] = { .type = NLA_U32, },

Oh thanks, I missed it's auto-generated.

Btw I needed the change below to generate the diff above
by "./tools/net/ynl/ynl-regen.sh -f".  Maybe depending on


diff --git a/tools/net/ynl/ynl-regen.sh b/tools/net/ynl/ynl-regen.sh
index 81b4ecd891006..fda5fe24cfd47 100755
--- a/tools/net/ynl/ynl-regen.sh
+++ b/tools/net/ynl/ynl-regen.sh
@@ -29,9 +29,9 @@ for f in $files; do
  continue
     fi

-    echo -e "\tGEN ${params[2]}\t$f"
-    $TOOL --cmp-out --mode ${params[2]} --${params[3]} \
-   --spec $KDIR/${params[0]} $args -o $f
+    echo -e "\tGEN ${params[5]}\t$f"
+    $TOOL --cmp-out --mode ${params[4]} --${params[5]} \
+   --spec $KDIR/${params[1]} $args -o $f
 done

 popd >>/dev/null


fwiw, $params were like

3- Documentation/netlink/specs/fou.yaml
4: YNL-GEN kernel source
--
3- Documentation/netlink/specs/fou.yaml
4: YNL-GEN kernel header