Re: [PATCH net-next v1 4/4] net: hsr: reject unresolved interlink ifindex

Felix Maurer
2026-03-26T14:30:28Z

On Tue, Mar 24, 2026 at 03:35:03PM +0100, luka.gejak@linux.dev wrote:
> From: Luka Gejak <luka.gejak@linux.dev>
>
> In hsr_newlink(), a provided but invalid IFLA_HSR_INTERLINK attribute
> was silently ignored if __dev_get_by_index() returned NULL. This leads
> to incorrect RedBox topology creation without notifying the user.

Not really incorrect, it's just not a RedBox at all.

> Fix this by returning -EINVAL and an extack message when the
> interlink attribute is present but cannot be resolved.
>
> Signed-off-by: Luka Gejak <luka.gejak@linux.dev>

Reviewed-by: Felix Maurer <fmaurer@redhat.com>

> ---
> net/hsr/hsr_netlink.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/net/hsr/hsr_netlink.c b/net/hsr/hsr_netlink.c
> index db0b0af7a692..f0ca23da3ab9 100644
> --- a/net/hsr/hsr_netlink.c
> +++ b/net/hsr/hsr_netlink.c
> @@ -76,9 +76,14 @@ static int hsr_newlink(struct net_device *dev,
> return -EINVAL;
> }
>
> - if (data[IFLA_HSR_INTERLINK])
> + if (data[IFLA_HSR_INTERLINK]) {
> interlink = __dev_get_by_index(link_net,
> nla_get_u32(data[IFLA_HSR_INTERLINK]));
> + if (!interlink) {
> + NL_SET_ERR_MSG_MOD(extack, "Interlink does not exist");
> + return -EINVAL;
> + }
> + }
>
> if (interlink && interlink == link[0]) {
> NL_SET_ERR_MSG_MOD(extack, "Interlink and Slave1 are the same");
> --
> 2.53.0
>