Re: [PATCH net] ice: fix vf->num_mac count with port representors

[Simon Horman <horms@kernel.org>]

On Thu, Apr 10, 2025 at 11:13:52AM -0700, Jacob Keller wrote:
> The ice_vc_repr_add_mac() function indicates that it does not store the MAC
> address filters in the firmware. However, it still increments vf->num_mac.
> This is incorrect, as vf->num_mac should represent the number of MAC
> filters currently programmed to firmware.
> 
> Indeed, we only perform this increment if the requested filter is a unicast
> address that doesn't match the existing vf->hw_lan_addr. In addition,
> ice_vc_repr_del_mac() does not decrement the vf->num_mac counter. This
> results in the counter becoming out of sync with the actual count.
> 
> As it turns out, vf->num_mac is currently only used in legacy made without
> port representors. The single place where the value is checked is for
> enforcing a filter limit on untrusted VFs.
> 
> Upcoming patches to support VF Live Migration will use this value when
> determining the size of the TLV for MAC address filters. Fix the
> representor mode function to stop incrementing the counter incorrectly.
> 
> Fixes: ac19e03ef780 ("ice: allow process VF opcodes in different ways")
> Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
> ---
> I am not certain if there is currently a way to trigger a bug from
> userspace due to this incorrect count, but I think it still warrants a net
> fix.

Reviewed-by: Simon Horman <horms@kernel.org>