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Message-ID: <20171107083105.6998b182@vento.lan>
Date: Tue, 7 Nov 2017 08:31:05 -0200
From: Mauro Carvalho Chehab <mchehab@...pensource.com>
To: Matthias Schwarzott <zzam@...too.org>,
Andrey Konovalov <andreyknvl@...gle.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>,
Max Kellermann <max.kellermann@...il.com>,
linux-media@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
Dmitry Vyukov <dvyukov@...gle.com>,
Kostya Serebryany <kcc@...gle.com>,
syzkaller <syzkaller@...glegroups.com>
Subject: Re: usb/media/dtt200u: use-after-free in __dvb_frontend_free
Em Mon, 23 Oct 2017 20:58:09 +0200
Matthias Schwarzott <zzam@...too.org> escreveu:
> 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?
The problem with (1) is that drivers may need to use frontend_priv
on their own release callbacks.
So, I don't think this is the right fix.
I guess option (2) is the best one here.
Andrey,
Could you please test the enclosed patch?
Thanks!
Mauro
dvb_frontend: don't use-after-free the frontend struct
dvb_frontend_invoke_release() may free the frontend struct.
So, we can't update it anymore after calling it.
That's OK, as __dvb_frontend_free() is called only when the
krefs are zeroed, so nobody is using it anymore.
Signed-off-by: Mauro Carvalho Chehab <mchehab@...pensource.com>
diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
index daaf969719e4..80191a15cd89 100644
--- a/drivers/media/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb-core/dvb_frontend.c
@@ -153,7 +153,6 @@ static void __dvb_frontend_free(struct dvb_frontend *fe)
dvb_frontend_invoke_release(fe, fe->ops.release);
kfree(fepriv);
- fe->frontend_priv = NULL;
}
static void dvb_frontend_free(struct kref *ref)
Thanks,
Mauro
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