From patchwork Thu Jun 23 12:50:59 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lukas Wunner X-Patchwork-Id: 585094 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0D321C433EF for ; Thu, 23 Jun 2022 12:51:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231436AbiFWMvy (ORCPT ); Thu, 23 Jun 2022 08:51:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34922 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229765AbiFWMvw (ORCPT ); Thu, 23 Jun 2022 08:51:52 -0400 Received: from mailout2.hostsharing.net (mailout2.hostsharing.net [IPv6:2a01:37:3000::53df:4ee9:0]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0EDFA46CB1; Thu, 23 Jun 2022 05:51:51 -0700 (PDT) Received: from h08.hostsharing.net (h08.hostsharing.net [83.223.95.28]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "*.hostsharing.net", Issuer "RapidSSL TLS DV RSA Mixed SHA256 2020 CA-1" (verified OK)) by mailout2.hostsharing.net (Postfix) with ESMTPS id 22EA4103B3F0B; Thu, 23 Jun 2022 14:51:49 +0200 (CEST) Received: from localhost (unknown [89.246.108.87]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by h08.hostsharing.net (Postfix) with ESMTPSA id E8B8E6021256; Thu, 23 Jun 2022 14:51:48 +0200 (CEST) X-Mailbox-Line: From d1c87ebe9fc502bffcd1576e238d685ad08321e4 Mon Sep 17 00:00:00 2001 Message-Id: From: Lukas Wunner Date: Thu, 23 Jun 2022 14:50:59 +0200 Subject: [PATCH net-next v2] usbnet: Fix linkwatch use-after-free on disconnect To: Oliver Neukum , "David S. Miller" , Jakub Kicinski , Paolo Abeni , Jann Horn , Oleksij Rempel , Oleksij Rempel , Eric Dumazet Cc: netdev@vger.kernel.org, linux-usb@vger.kernel.org, Andrew Lunn , Jacky Chou , Willy Tarreau , Lino Sanfilippo , Philipp Rosenberger , Heiner Kallweit Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org usbnet uses the work usbnet_deferred_kevent() to perform tasks which may sleep. On disconnect, completion of the work was originally awaited in ->ndo_stop(). But in 2003, that was moved to ->disconnect() by historic commit "[PATCH] USB: usbnet, prevent exotic rtnl deadlock": https://git.kernel.org/tglx/history/c/0f138bbfd83c The change was made because back then, the kernel's workqueue implementation did not allow waiting for a single work. One had to wait for completion of *all* work by calling flush_scheduled_work(), and that could deadlock when waiting for usbnet_deferred_kevent() with rtnl_mutex held in ->ndo_stop(). The commit solved one problem but created another: It causes a use-after-free in USB Ethernet drivers aqc111.c, asix_devices.c, ax88179_178a.c, ch9200.c and smsc75xx.c: * If the drivers receive a link change interrupt immediately before disconnect, they raise EVENT_LINK_RESET in their (non-sleepable) ->status() callback and schedule usbnet_deferred_kevent(). * usbnet_deferred_kevent() invokes the driver's ->link_reset() callback, which calls netif_carrier_{on,off}(). * That in turn schedules the work linkwatch_event(). Because usbnet_deferred_kevent() is awaited after unregister_netdev(), netif_carrier_{on,off}() may operate on an unregistered netdev and linkwatch_event() may run after free_netdev(), causing a use-after-free. In 2010, usbnet was changed to only wait for a single instance of usbnet_deferred_kevent() instead of *all* work by commit 23f333a2bfaf ("drivers/net: don't use flush_scheduled_work()"). Unfortunately the commit neglected to move the wait back to ->ndo_stop(). Rectify that omission at long last. Reported-by: Jann Horn Link: https://lore.kernel.org/netdev/CAG48ez0MHBbENX5gCdHAUXZ7h7s20LnepBF-pa5M=7Bi-jZrEA@mail.gmail.com/ Reported-by: Oleksij Rempel Link: https://lore.kernel.org/netdev/20220315113841.GA22337@pengutronix.de/ Signed-off-by: Lukas Wunner Cc: stable@vger.kernel.org Cc: Oliver Neukum --- This seems to be Jakub's preferred way to solve the use-after-free. I've tagged the patch for net-next so that it can bake in linux-next for a few weeks, but it alternatively applies cleanly to net (in case maintainers are eager to get it into mainline). The patch supersedes the following prior attempts: usbnet: Fix use-after-free on disconnect https://lore.kernel.org/netdev/127121d9d933ebe3fc13f9f91cc33363d6a8a8ac.1649859147.git.lukas@wunner.de/ net: linkwatch: ignore events for unregistered netdevs https://lore.kernel.org/netdev/18b3541e5372bc9b9fc733d422f4e698c089077c.1650177997.git.lukas@wunner.de/ net: linkwatch: ignore events for unregistered netdevs (v2) https://lore.kernel.org/netdev/cover.1655024266.git.lukas@wunner.de/ drivers/net/usb/usbnet.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c index dc79811535c2..63868c1fbea4 100644 --- a/drivers/net/usb/usbnet.c +++ b/drivers/net/usb/usbnet.c @@ -849,13 +849,11 @@ int usbnet_stop (struct net_device *net) mpn = !test_and_clear_bit(EVENT_NO_RUNTIME_PM, &dev->flags); - /* deferred work (task, timer, softirq) must also stop. - * can't flush_scheduled_work() until we drop rtnl (later), - * else workers could deadlock; so make workers a NOP. - */ + /* deferred work (timer, softirq, task) must also stop */ dev->flags = 0; del_timer_sync (&dev->delay); tasklet_kill (&dev->bh); + cancel_work_sync(&dev->kevent); if (!pm) usb_autopm_put_interface(dev->intf); @@ -1619,8 +1617,6 @@ void usbnet_disconnect (struct usb_interface *intf) net = dev->net; unregister_netdev (net); - cancel_work_sync(&dev->kevent); - usb_scuttle_anchored_urbs(&dev->deferred); if (dev->driver_info->unbind)