Re: [PATCH net-next] net: bridge: cfm: notify userspace on CFM config changes

[Abdul Wasey]

On Mon, 05 Oct 2026 04:16:29 +0000, netdev-bot+sashiko@xxxxxxxxxx wrote:
> [Severity: High]
> Is the skb that br_info_notify() allocates large enough for a message
> with only RTEXT_FILTER_CFM_CONFIG set?

Right, this is a real bug. br_get_link_af_size_filtered() never counts
the config attributes, so the notification only fit for small configs.
I reproduced it: with one MEP and about 32 peer MEPs every config change
hits the WARN_ON in br_info_notify() and the notification is lost.

v2 adds a patch before this one that counts the config attributes when
RTEXT_FILTER_CFM_CONFIG is set.

> [Severity: Medium]
> What does userspace receive when this request deletes the last MEP?

Right, it gets an RTM_NEWLINK with no IFLA_BRIDGE_CFM at all, which
can't be told apart from other bridge notifications. v2 sends an empty
IFLA_BRIDGE_CFM nest for a bridge with no MEPs, so that case is visible.

pw-bot: cr