usb/media/dtt200u: use-after-free in __dvb_frontend_free

[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

Allocated by task 24:
save_stack_trace+0x1b/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459
kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
kmem_cache_alloc_trace+0x11e/0x2d0 mm/slub.c:2772
kmalloc ./include/linux/slab.h:493
kzalloc ./include/linux/slab.h:666
dtt200u_fe_attach+0x4c/0x110 drivers/media/usb/dvb-usb/dtt200u-fe.c:212
dtt200u_frontend_attach+0x35/0x80 drivers/media/usb/dvb-usb/dtt200u.c:136
dvb_usb_adapter_frontend_init+0x32b/0x660
drivers/media/usb/dvb-usb/dvb-usb-dvb.c:286
dvb_usb_adapter_init drivers/media/usb/dvb-usb/dvb-usb-init.c:86
dvb_usb_init drivers/media/usb/dvb-usb/dvb-usb-init.c:162
dvb_usb_device_init+0xf73/0x17f0 drivers/media/usb/dvb-usb/dvb-usb-init.c:277
dtt200u_usb_probe+0xa1/0xe0 drivers/media/usb/dvb-usb/dtt200u.c:155
usb_probe_interface+0x35d/0x8e0 drivers/usb/core/driver.c:361
really_probe drivers/base/dd.c:413
driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
__device_attach_driver+0x230/0x290 drivers/base/dd.c:653
bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
__device_attach+0x26b/0x3c0 drivers/base/dd.c:710
device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
device_add+0xd0b/0x1660 drivers/base/core.c:1835
usb_set_configuration+0x104e/0x1870 drivers/usb/core/message.c:1932
generic_probe+0x73/0xe0 drivers/usb/core/generic.c:174
usb_probe_device+0xaf/0xe0 drivers/usb/core/driver.c:266
really_probe drivers/base/dd.c:413
driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
__device_attach_driver+0x230/0x290 drivers/base/dd.c:653
bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
__device_attach+0x26b/0x3c0 drivers/base/dd.c:710
device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
device_add+0xd0b/0x1660 drivers/base/core.c:1835
usb_new_device+0x7b8/0x1020 drivers/usb/core/hub.c:2457
hub_port_connect drivers/usb/core/hub.c:4903
hub_port_connect_change drivers/usb/core/hub.c:5009
port_event drivers/usb/core/hub.c:5115
hub_event+0x194d/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

Freed by task 24:
save_stack_trace+0x1b/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459
kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:524
slab_free_hook mm/slub.c:1390
slab_free_freelist_hook mm/slub.c:1412
slab_free mm/slub.c:2988
kfree+0xf6/0x2f0 mm/slub.c:3919
dtt200u_fe_release+0x3c/0x50 drivers/media/usb/dvb-usb/dtt200u-fe.c:202
dvb_frontend_invoke_release.part.13+0x1c/0x30
drivers/media/dvb-core/dvb_frontend.c:2790
dvb_frontend_invoke_release drivers/media/dvb-core/dvb_frontend.c:2789
__dvb_frontend_free+0xad/0x120 drivers/media/dvb-core/dvb_frontend.c:153
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

The buggy address belongs to the object at ffff880067d45500
which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1280 bytes inside of
2048-byte region [ffff880067d45500, ffff880067d45d00)
The buggy address belongs to the page:
page:ffffea00019f5000 count:1 mapcount:0 mapping: (null)
index:0x0 compound_mapcount: 0
flags: 0x100000000008100(slab|head)
raw: 0100000000008100 0000000000000000 0000000000000000 00000001000f000f
raw: dead000000000100 dead000000000200 ffff88006c002d80 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff880067d45900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff880067d45980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff880067d45a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff880067d45a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff880067d45b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

[Matthias Schwarzott]

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)

[Andrey Konovalov]

Hi Matthias,

Your patch fixes the issue.

Thanks!

Tested-by: Andrey Konovalov <andre...@google.com>

[Mauro Carvalho Chehab]

Em Mon, 23 Oct 2017 20:58:09 +0200
Matthias Schwarzott <zz...@gentoo.org> escreveu:

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 <mch...@s-opensource.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

[Andrey Konovalov]

Hi Mauro,

This patch also fixes the issue.

Thanks!

Tested-by: Andrey Konovalov <andre...@google.com>

>