Re: [PATCH net v2 2/2] geneve: require CAP_NET_ADMIN in the device netns for changelink

[Fernando Fernandez Mancera]

On Thu, 16 Jul 2026 22:35:00 +0200, Doruk Tan Ozturk <doruk@xxxxxxx> wrote:
> A tunnel changelink() operates on at most two netns, dev_net(dev) and
> the sticky underlay netns geneve->net. They differ once the device is
> created in or moved to a netns other than the one the request runs in.
> The rtnl changelink path checks CAP_NET_ADMIN only against dev_net(dev),
> so a caller privileged there but not in geneve->net can rewrite a geneve
> device whose underlay lives in geneve->net.
> 
> geneve_changelink() applies the new configuration against geneve->net:
> geneve_link_config() and the geneve_quiesce()/geneve_unquiesce() pair
> reopen the underlay sockets in that netns (geneve_sock_add() uses
> geneve->net), so the same reasoning as the tunnel changelink series
> applies here.
> 
> Gate geneve_changelink() with rtnl_dev_link_net_capable(), at the top of
> the op before any attribute is parsed, matching ipgre_changelink() and
> the rest of the "require CAP_NET_ADMIN in the device netns for
> changelink" series.
> 
> Found by 0sec automated security-research tooling (https://0sec.ai).
> 
> Fixes: 5b861f6baa3a ("geneve: add rtnl changelink support")
> Cc: stable@xxxxxxxxxxxxxxx
> Assisted-by: 0sec:multi-model
> Signed-off-by: Doruk Tan Ozturk <doruk@xxxxxxx>
>

Reviewed-by: Fernando Fernandez Mancera <fmancera@xxxxxxx>

Thanks!