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geneve: require CAP_NET_ADMIN in the device netns for changelink

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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: 5b861f6baa ("geneve: add rtnl changelink support")
Cc: stable@vger.kernel.org
Signed-off-by: Doruk Tan Ozturk <doruk@0sec.ai>
Reviewed-by: Fernando Fernandez Mancera <fmancera@suse.de>
Link: https://patch.msgid.link/20260716203500.70573-3-doruk@0sec.ai
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Doruk Tan Ozturk 2026-07-16 22:35:00 +02:00 committed by Jakub Kicinski
parent 3a61bd9637
commit 8efb8f8bbb
1 changed files with 3 additions and 0 deletions
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3
drivers/net/geneve.c
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@ -2394,6 +2394,9 @@ static int geneve_changelink(struct net_device *dev, struct nlattr *tb[],
struct geneve_config cfg;
int err;
if (!rtnl_dev_link_net_capable(dev, geneve->net))
return -EPERM;
/* If the geneve device is configured for metadata (or externally
* controlled, for example, OVS), then nothing can be changed.
*/