From: Doruk Tan Ozturk Date: Thu, 16 Jul 2026 20:34:59 +0000 (+0200) Subject: vxlan: require CAP_NET_ADMIN in the device netns for changelink X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=3a61bd9637f3d929aa846e4eb3d98b48c26fcb0e;p=thirdparty%2Fkernel%2Flinux.git vxlan: require CAP_NET_ADMIN in the device netns for changelink A tunnel changelink() operates on at most two netns, dev_net(dev) and the sticky underlay netns vxlan->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 vxlan->net can rewrite a vxlan device whose underlay lives in vxlan->net. vxlan_changelink() validates and applies the new configuration against vxlan->net (vxlan_config_validate(vxlan->net, ...)) and can reopen the underlay socket in that netns, so the same reasoning as the tunnel changelink series applies here. Gate vxlan_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: 8bcdc4f3a20b ("vxlan: add changelink support") Cc: stable@vger.kernel.org Signed-off-by: Doruk Tan Ozturk Reviewed-by: Fernando Fernandez Mancera Link: https://patch.msgid.link/20260716203500.70573-2-doruk@0sec.ai Signed-off-by: Jakub Kicinski --- diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c index 67c367cc5662..d834a4865aec 100644 --- a/drivers/net/vxlan/vxlan_core.c +++ b/drivers/net/vxlan/vxlan_core.c @@ -4421,6 +4421,9 @@ static int vxlan_changelink(struct net_device *dev, struct nlattr *tb[], struct vxlan_rdst *dst; int err; + if (!rtnl_dev_link_net_capable(dev, vxlan->net)) + return -EPERM; + dst = &vxlan->default_dst; err = vxlan_nl2conf(tb, data, dev, &conf, true, extack); if (err)