From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Doruk Tan Ozturk <doruk@0sec.ai>,
	Fernando Fernandez Mancera <fmancera@suse.de>,
	Jakub Kicinski <kuba@kernel.org>
Subject: [PATCH 5.10 172/389] geneve: require CAP_NET_ADMIN in the device netns for changelink
Date: Mon, 17 Aug 2026 15:30:11 +0200
Message-ID: <20260817132545.880479844@linuxfoundation.org>
In-Reply-To: <20260817132538.796021292@linuxfoundation.org>
References: <20260817132538.796021292@linuxfoundation.org>
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5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Doruk Tan Ozturk <doruk@0sec.ai>

commit 8efb8f8bbb353b8f2fdf4f37534c6d96c9f69e01 upstream.

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@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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/geneve.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -1751,6 +1751,9 @@ static int geneve_changelink(struct net_
 	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.
 	 */