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Tue, 14 Jul 2026 22:56:52 -0700 (PDT) From: Doruk Tan Ozturk To: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, andrew+netdev@lunn.ch Cc: sd@queasysnail.net, linville@tuxdriver.com, mschiffer@universe-factory.net, maoyixie.tju@gmail.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH net 2/2] geneve: require CAP_NET_ADMIN in the device netns for changelink Date: Wed, 15 Jul 2026 07:56:48 +0200 Message-ID: <20260715055648.33060-3-doruk@0sec.ai> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260715055648.33060-1-doruk@0sec.ai> References: <20260715055648.33060-1-doruk@0sec.ai> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: 2d07dc79fe04 ("geneve: add initial netdev driver for GENEVE tunnels") Cc: stable@vger.kernel.org Assisted-by: 0sec:multi-model Signed-off-by: Doruk Tan Ozturk --- drivers/net/geneve.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c index 396e1a113cd4..03c99a016298 100644 --- a/drivers/net/geneve.c +++ b/drivers/net/geneve.c @@ -2376,6 +2376,9 @@ 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. */ -- 2.43.0