[{"id":3685065,"web_url":"http://patchwork.ozlabs.org/comment/3685065/","msgid":"<17BF3316-75E2-46EA-A603-0F6B87FBD98F@redhat.com>","list_archive_url":null,"date":"2026-05-01T08:53:23","subject":"Re: [ovs-dev] [PATCH net] openvswitch: vport: fix race between\n tunnel creation and linking","submitter":{"id":70613,"url":"http://patchwork.ozlabs.org/api/people/70613/","name":"Eelco Chaudron","email":"echaudro@redhat.com"},"content":"On 30 Apr 2026, at 23:32, Ilya Maximets wrote:\n\n> When a tunnel vport is created it first creates the tunnel device, e.g.,\n> with geneve_dev_create_fb(), then it calls ovs_netdev_link() to take a\n> reference and link it to the device that represents openvswitch datapath.\n>\n> The creation of the device is happening under RTNL, but then RTNL is\n> released and re-acquired to find the device by name. It is technically\n> possible for the tunnel device to be re-named or deleted within that\n> window while RTNL is not held, and some other device created in its\n> place. This will cause a non-tunnel device to be referenced in the\n> vport and tunnel-specific functions used on it, e.g. vxlan_get_options()\n> that directly casts the private netdev data into a struct vxlan_dev\n> causing an invalid memory access:\n>\n> BUG: KASAN: slab-use-after-free in vxlan_get_options+0x323/0x3a0\n> vxlan_get_options+0x323/0x3a0\n> ovs_vport_cmd_new+0x6e3/0xd30\n>\n> Fix that by taking a reference to the just created device before\n> releasing RTNL. This ensures that the device in the vport is always\n> the one that was just created. The search by name is only needed\n> for a standard vport-netdev that links pre-existing devices, so that\n> functionality and device type checks are moved to netdev_create().\n>\n> It is also awkward that ovs_netdev_link() takes ownership of the vport\n> and destroys it on failure. It doesn't know the type of the port it is\n> dealing with, so we need to pass down the indicator that it's a tunnel,\n> so the link can be properly deleted on failure.\n>\n> It's possible to refactor the logic to make the ovs_netdev_link() do\n> only the linking part and let the callers perform a proper destruction,\n> but it will be much more code for each legacy tunnel port type, so it\n> is not worth it for the bug fix.\n>\n> Fixes: 614732eaa12d (\"openvswitch: Use regular VXLAN net_device device\")\n> Reported-by: Yuan Tan \n> Reported-by: Yifan Wu \n> Reported-by: Juefei Pu \n> Reported-by: Xin Liu \n> Reported-by: Yang Yang \n> Signed-off-by: Ilya Maximets \n\nThanks for working on this Ilya! The changes look good to me.\n\nAcked-by: Eelco Chaudron ","headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","dev@openvswitch.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","ovs-dev@lists.linuxfoundation.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=fail reason=\"signature verification failed\" (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=ca4TDsdZ;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=openvswitch.org\n (client-ip=2605:bc80:3010::136; helo=smtp3.osuosl.org;\n envelope-from=ovs-dev-bounces@openvswitch.org; receiver=patchwork.ozlabs.org)","smtp3.osuosl.org;\n\tdkim=fail reason=\"signature verification failed\" (1024-bit key,\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=ca4TDsdZ","smtp4.osuosl.org; dmarc=pass (p=quarantine dis=none)\n header.from=redhat.com","smtp4.osuosl.org; 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