From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751734AbdJWS57 (ORCPT ); Mon, 23 Oct 2017 14:57:59 -0400 Received: from smtp.gentoo.org ([140.211.166.183]:42480 "EHLO smtp.gentoo.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751662AbdJWS56 (ORCPT ); Mon, 23 Oct 2017 14:57:58 -0400 Subject: Re: usb/media/dtt200u: use-after-free in __dvb_frontend_free To: Andrey Konovalov , Mauro Carvalho Chehab , Max Kellermann , linux-media@vger.kernel.org, LKML Cc: Dmitry Vyukov , Kostya Serebryany , syzkaller References: From: Matthias Schwarzott Message-ID: Date: Mon, 23 Oct 2017 20:58:09 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 23.10.2017 um 16:41 schrieb Andrey Konovalov: > Hi! > > I've got the following report while fuzzing the kernel with syzkaller. > > On commit 3e0cc09a3a2c40ec1ffb6b4e12da86e98feccb11 (4.14-rc5+). > > dvb-usb: found a 'WideView WT-220U PenType Receiver (based on ZL353)' > in warm state. > dvb-usb: bulk message failed: -22 (2/1102416563) > dvb-usb: will use the device's hardware PID filter (table count: 15). > dvbdev: DVB: registering new adapter (WideView WT-220U PenType > Receiver (based on ZL353)) > usb 1-1: media controller created > dvbdev: dvb_create_media_entity: media entity 'dvb-demux' registered. > usb 1-1: DVB: registering adapter 0 frontend 0 (WideView USB DVB-T)... > dvbdev: dvb_create_media_entity: media entity 'WideView USB DVB-T' registered. > Registered IR keymap rc-dtt200u > rc rc1: IR-receiver inside an USB DVB receiver as > /devices/platform/dummy_hcd.0/usb1/1-1/rc/rc1 > input: IR-receiver inside an USB DVB receiver as > /devices/platform/dummy_hcd.0/usb1/1-1/rc/rc1/input9 > dvb-usb: schedule remote query interval to 300 msecs. > dvb-usb: WideView WT-220U PenType Receiver (based on ZL353) > successfully initialized and connected. > dvb-usb: bulk message failed: -22 (1/1807119384) > dvb-usb: error -22 while querying for an remote control event. > dvb-usb: bulk message failed: -22 (1/1807119384) > dvb-usb: error -22 while querying for an remote control event. > dvb-usb: bulk message failed: -22 (1/1807119384) > dvb-usb: error -22 while querying for an remote control event. > dvb-usb: bulk message failed: -22 (1/1807119384) > dvb-usb: error -22 while querying for an remote control event. > dvb-usb: bulk message failed: -22 (1/1807119384) > dvb-usb: error -22 while querying for an remote control event. > dvb-usb: bulk message failed: -22 (1/1807119384) > dvb-usb: error -22 while querying for an remote control event. > usb 1-1: USB disconnect, device number 2 > ================================================================== > BUG: KASAN: use-after-free in __dvb_frontend_free+0x113/0x120 > Write of size 8 at addr ffff880067d45a00 by task kworker/0:1/24 > > CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted 4.14.0-rc5-43687-g06ab8a23e0e6 #545 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > Workqueue: usb_hub_wq hub_event > Call Trace: > __dump_stack lib/dump_stack.c:16 > dump_stack+0x292/0x395 lib/dump_stack.c:52 > print_address_description+0x78/0x280 mm/kasan/report.c:252 > kasan_report_error mm/kasan/report.c:351 > kasan_report+0x23d/0x350 mm/kasan/report.c:409 > __asan_report_store8_noabort+0x1c/0x20 mm/kasan/report.c:435 > __dvb_frontend_free+0x113/0x120 drivers/media/dvb-core/dvb_frontend.c:156 > dvb_frontend_put+0x59/0x70 drivers/media/dvb-core/dvb_frontend.c:176 > dvb_frontend_detach+0x120/0x150 drivers/media/dvb-core/dvb_frontend.c:2803 > dvb_usb_adapter_frontend_exit+0xd6/0x160 > drivers/media/usb/dvb-usb/dvb-usb-dvb.c:340 > dvb_usb_adapter_exit drivers/media/usb/dvb-usb/dvb-usb-init.c:116 > dvb_usb_exit+0x9b/0x200 drivers/media/usb/dvb-usb/dvb-usb-init.c:132 > dvb_usb_device_exit+0xa5/0xf0 drivers/media/usb/dvb-usb/dvb-usb-init.c:295 > usb_unbind_interface+0x21c/0xa90 drivers/usb/core/driver.c:423 > __device_release_driver drivers/base/dd.c:861 > device_release_driver_internal+0x4f1/0x5c0 drivers/base/dd.c:893 > device_release_driver+0x1e/0x30 drivers/base/dd.c:918 > bus_remove_device+0x2f4/0x4b0 drivers/base/bus.c:565 > device_del+0x5c4/0xab0 drivers/base/core.c:1985 > usb_disable_device+0x1e9/0x680 drivers/usb/core/message.c:1170 > usb_disconnect+0x260/0x7a0 drivers/usb/core/hub.c:2124 > hub_port_connect drivers/usb/core/hub.c:4754 > hub_port_connect_change drivers/usb/core/hub.c:5009 > port_event drivers/usb/core/hub.c:5115 > hub_event+0x1318/0x3740 drivers/usb/core/hub.c:5195 > process_one_work+0xc73/0x1d90 kernel/workqueue.c:2119 > worker_thread+0x221/0x1850 kernel/workqueue.c:2253 > kthread+0x363/0x440 kernel/kthread.c:231 > ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431 > It looks like this is caused by commit ead666000a5fe34bdc82d61838e4df2d416ea15e ("media: dvb_frontend: only use kref after initialized"). The writing to "fe->frontend_priv" in dvb_frontend.c:156 is a use-after-free in case the object dvb_frontend *fe is already freed by the release callback called in line 153. Only if the demod driver is based on new style i2c_client the memory is still accessible. There are two possible solutions: 1. Clear fe->frontend_priv earlier (before line 153). 2. Do not clear fe->frontend_priv Can you try if the following patch (solution 1) fixes the issue? Regards Matthias diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c index daaf969719e4..f552acdb7d8c 100644 --- a/drivers/media/dvb-core/dvb_frontend.c +++ b/drivers/media/dvb-core/dvb_frontend.c @@ -150,10 +150,11 @@ static void __dvb_frontend_free(struct dvb_frontend *fe) dvb_free_device(fepriv->dvbdev); + fe->frontend_priv = NULL; + dvb_frontend_invoke_release(fe, fe->ops.release); kfree(fepriv); - fe->frontend_priv = NULL; } static void dvb_frontend_free(struct kref *ref)