Re: [PATCH net v2] macsec: initialize SecY before registering the netdevice

[Sabrina Dubroca <sd@queasysnail.net>]

2026-09-18, 15:01:29 -0400, Haseeb Malik via B4 Relay wrote:
> From: Haseeb Malik <haseebulhaq55@gmail.com>
> 
> Creating a MACsec device with MAC offload over an LRO-capable lower
> device triggers a warning in rtmsg_ifinfo_build_skb() when IPv4
> forwarding is enabled by default.
> 
> register_netdevice() invokes inetdev_init(), which disables LRO and emits
> a NETDEV_FEAT_CHANGE notification. This reaches macsec_fill_info() before
> macsec_add_dev() initializes the SecY. key_len is still zero, so
> macsec_fill_info() returns -EMSGSIZE and trips the WARN_ON in
> rtmsg_ifinfo_build_skb(), even though the skb has enough space.
> 
> Initialize the SecY and apply the new-link attributes before registration.
> Move MAC address inheritance into macsec_newlink() so the SCI can also be
> initialized before registration-time notifications report it. Move the
> per-CPU statistics and metadata destination allocation into ndo_init(),
> and release partial allocations on failure.
> 
> Fixes: ccfdec908922 ("macsec: Add support for GCM-AES-256 cipher suite")

Why this commit? The "register, then init SCI etc" order of operations
has existed since day 1. Without ccfdec908922 we don't hit the WARN_ON
in rtmsg_ifinfo_build_skb, but the bit fixed by "Registration can
notify listeners before returning." would still be bogus.

The patch itself looks ok. Thanks for picking this up, things got
crazy and I forgot about it.

-- 
Sabrina