Re: [PATCH net 2/2] drop_monitor: Require 'CAP_SYS_ADMIN' when joining "events" group

[Jacob Keller <jacob.e.keller@intel.com>]

On 12/6/2023 1:31 PM, Ido Schimmel wrote:
> The "NET_DM" generic netlink family notifies drop locations over the
> "events" multicast group. This is problematic since by default generic
> netlink allows non-root users to listen to these notifications.
> 
> Fix by adding a new field to the generic netlink multicast group
> structure that when set prevents non-root users or root without the
> 'CAP_SYS_ADMIN' capability (in the user namespace owning the network
> namespace) from joining the group. Set this field for the "events"
> group. Use 'CAP_SYS_ADMIN' rather than 'CAP_NET_ADMIN' because of the
> nature of the information that is shared over this group.
> 
> Note that the capability check in this case will always be performed
> against the initial user namespace since the family is not netns aware
> and only operates in the initial network namespace.
> 
> A new field is added to the structure rather than using the "flags"
> field because the existing field uses uAPI flags and it is inappropriate
> to add a new uAPI flag for an internal kernel check. In net-next we can
> rework the "flags" field to use internal flags and fold the new field
> into it. But for now, in order to reduce the amount of changes, add a
> new field.
> 
> Since the information can only be consumed by root, mark the control
> plane operations that start and stop the tracing as root-only using the
> 'GENL_ADMIN_PERM' flag.
> 

Makes sense.

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>