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[2620:137:e000::1:20]) by mx.google.com with ESMTP id l15-20020a170903244f00b0018388edd187si5518734pls.56.2022.11.04.06.11.22; Fri, 04 Nov 2022 06:11:36 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231747AbiKDNKn (ORCPT + 99 others); Fri, 4 Nov 2022 09:10:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45770 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231634AbiKDNKi (ORCPT ); Fri, 4 Nov 2022 09:10:38 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0B2A42CDDA for ; Fri, 4 Nov 2022 06:10:37 -0700 (PDT) Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1oqwSw-0000Yo-Sl; Fri, 04 Nov 2022 14:10:34 +0100 Received: from [2a0a:edc0:0:1101:1d::28] (helo=dude02.red.stw.pengutronix.de) by drehscheibe.grey.stw.pengutronix.de with esmtp (Exim 4.94.2) (envelope-from ) id 1oqwSx-002HHl-3T; Fri, 04 Nov 2022 14:10:34 +0100 Received: from sha by dude02.red.stw.pengutronix.de with local (Exim 4.94.2) (envelope-from ) id 1oqwSv-004043-44; Fri, 04 Nov 2022 14:10:33 +0100 From: Sascha Hauer To: linux-usb@vger.kernel.org Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, kernel@pengutronix.de, Sascha Hauer Subject: [PATCH 1/2] usb: gadget: u_ether: Do not make UDC parent of the net device Date: Fri, 4 Nov 2022 14:10:30 +0100 Message-Id: <20221104131031.850850-2-s.hauer@pengutronix.de> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20221104131031.850850-1-s.hauer@pengutronix.de> References: <20221104131031.850850-1-s.hauer@pengutronix.de> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: sha@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1748571255867682636?= X-GMAIL-MSGID: =?utf-8?q?1748571255867682636?= The UDC is not a suitable parent of the net device as the UDC can change or vanish during the lifecycle of the ethernet gadget. This can be illustrated with the following: mkdir -p /sys/kernel/config/usb_gadget/mygadget cd /sys/kernel/config/usb_gadget/mygadget mkdir -p configs/c.1/strings/0x409 echo "C1:Composite Device" > configs/c.1/strings/0x409/configuration mkdir -p functions/ecm.usb0 ln -s functions/ecm.usb0 configs/c.1/ echo "dummy_udc.0" > UDC rmmod dummy_hcd The 'rmmod' removes the UDC from the just created gadget, leaving the still existing net device with a no longer existing parent. Accessing the ethernet device with commands like: ip --details link show usb0 will result in a KASAN splat: ================================================================== BUG: KASAN: use-after-free in if_nlmsg_size+0x3e8/0x528 Read of size 4 at addr c5c84754 by task ip/357 CPU: 3 PID: 357 Comm: ip Not tainted 6.1.0-rc3-00013-gd14953726b24-dirty #324 Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree) unwind_backtrace from show_stack+0x10/0x14 show_stack from dump_stack_lvl+0x58/0x70 dump_stack_lvl from print_report+0x134/0x4d4 print_report from kasan_report+0x78/0x10c kasan_report from if_nlmsg_size+0x3e8/0x528 if_nlmsg_size from rtnl_getlink+0x2b4/0x4d0 rtnl_getlink from rtnetlink_rcv_msg+0x1f4/0x674 rtnetlink_rcv_msg from netlink_rcv_skb+0xb4/0x1f8 netlink_rcv_skb from netlink_unicast+0x294/0x478 netlink_unicast from netlink_sendmsg+0x328/0x640 netlink_sendmsg from ____sys_sendmsg+0x2a4/0x3b4 ____sys_sendmsg from ___sys_sendmsg+0xc8/0x12c ___sys_sendmsg from sys_sendmsg+0xa0/0x120 sys_sendmsg from ret_fast_syscall+0x0/0x1c Solve this by not setting the parent of the ethernet device. Signed-off-by: Sascha Hauer --- drivers/usb/gadget/function/u_ether.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c index e06022873df16..8f12f3f8f6eeb 100644 --- a/drivers/usb/gadget/function/u_ether.c +++ b/drivers/usb/gadget/function/u_ether.c @@ -798,7 +798,6 @@ struct eth_dev *gether_setup_name(struct usb_gadget *g, net->max_mtu = GETHER_MAX_MTU_SIZE; dev->gadget = g; - SET_NETDEV_DEV(net, &g->dev); SET_NETDEV_DEVTYPE(net, &gadget_type); status = register_netdev(net); @@ -873,8 +872,6 @@ int gether_register_netdev(struct net_device *net) struct usb_gadget *g; int status; - if (!net->dev.parent) - return -EINVAL; dev = netdev_priv(net); g = dev->gadget; @@ -905,7 +902,6 @@ void gether_set_gadget(struct net_device *net, struct usb_gadget *g) dev = netdev_priv(net); dev->gadget = g; - SET_NETDEV_DEV(net, &g->dev); } EXPORT_SYMBOL_GPL(gether_set_gadget);