Re: [syzbot] [net?] WARNING in rtmsg_ifinfo_build_skb

On Sat, Aug 15, 2026 at 1:14 AM Sabrina Dubroca [off-list ref] wrote:

It's not possible to create a macsec device with a key length other
than those 2, but it's true that returning -EMSGSIZE in this case is
not correct (-EINVAL + DEBUG_NET_WARN_ON_ONCE I guess).

The real problem is that we register the netdev before private data
has been fully initialized (macsec_newlink calls register_netdevice,
then macsec_add_dev), so we end up reaching fill_info before key_len
has been set.

SGTM, I let you send a patch.

So I think we should run macsec_add_dev before registering (and maybe
move those allocs to ndo_init), and possibly macsec_changelink_common
too. Setting the sci was intentionally done late, so this bit should
stay where it is.

Thanks