2026-03-11, 00:47:41 +0000, Hangbin Liu wrote:

On Tue, Mar 10, 2026 at 08:17:01PM +0100, Sabrina Dubroca wrote:

quoted

2026-03-10, 10:02:09 -0700, syzbot ci wrote:

quoted

batman_adv: batadv0: Not using interface batadv_slave_1 (retrying later): interface not active
hsr_slave_0: entered promiscuous mode
hsr_slave_1: entered promiscuous mode
------------[ cut here ]------------
err == -EMSGSIZE
WARNING: net/core/rtnetlink.c:4421 at rtmsg_ifinfo_build_skb+0x218/0x260, CPU#0: syz-executor/6496

I'm not sure this one is caused by this series, but either way,

 rtnetlink_event+0x1b7/0x270
 notifier_call_chain+0x1be/0x400
 netdev_change_features+0x95/0xe0
 __netdev_upper_dev_link+0xb20/0xc80
 netdev_upper_dev_link+0xb0/0x100


This patch calls netdev_change_features() after __netdev_upper_dev_link(),
Which trigger a NETDEV_FEAT_CHANGE notify and calls rtmsg_ifinfo_event()
to fill the new link info. Maybe the event is a bit early and macsec has
data not ready?

But this would still mean that there's a mismatch between
if_nlmsg_size() and rtnl_fill_ifinfo(), and your patch is only
revealing it.

I'll send fixes for the stuff I mentioned, no idea if that's what
syzbot saw since we don't have a repro.

-- 
Sabrina