Re: usb/media/em28xx: use-after-free in dvb_unregister_frontend

[Matthias Schwarzott]

Am 21.11.2017 um 14:51 schrieb Andrey Konovalov:
> Hi!
> 
Hi Andrey,

> I've got the following report while fuzzing the kernel with syzkaller.
> 
> On commit e1d1ea549b57790a3d8cf6300e6ef86118d692a3 (4.15-rc1).
> 
> em28xx 1-1:9.0: Disconnecting
> tc90522 1-0015: Toshiba TC90522 attached.
> qm1d1c0042 2-0061: Sharp QM1D1C0042 attached.
> dvbdev: DVB: registering new adapter (1-1:9.0)
> em28xx 1-1:9.0: DVB: registering adapter 0 frontend 0 (Toshiba TC90522
> ISDB-S module)...
> dvbdev: dvb_create_media_entity: media entity 'Toshiba TC90522 ISDB-S
> module' registered.
> dvbdev: dvb_create_media_entity: media entity 'dvb-demux' registered.
> em28xx 1-1:9.0: DVB extension successfully initialized
> em28xx 1-1:9.0: Remote control support is not available for this card.
> em28xx 1-1:9.0: Closing DVB extension
> ==================================================================
> BUG: KASAN: use-after-free in dvb_unregister_frontend+0x8f/0xa0
> Read of size 8 at addr ffff880067853628 by task kworker/0:3/3182
> 
> CPU: 0 PID: 3182 Comm: kworker/0:3 Not tainted 4.14.0-57501-g9284d204d604 #119
> 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:17
>  dump_stack+0xe1/0x157 lib/dump_stack.c:53
>  print_address_description+0x71/0x234 mm/kasan/report.c:252
>  kasan_report_error mm/kasan/report.c:351
>  kasan_report+0x173/0x270 mm/kasan/report.c:409
>  __asan_report_load8_noabort+0x19/0x20 mm/kasan/report.c:430
>  dvb_unregister_frontend+0x8f/0xa0 drivers/media/dvb-core/dvb_frontend.c:2768
>  em28xx_unregister_dvb drivers/media/usb/em28xx/em28xx-dvb.c:1122
>  em28xx_dvb_fini+0x62d/0x8e0 drivers/media/usb/em28xx/em28xx-dvb.c:2129
>  em28xx_close_extension+0x71/0x220 drivers/media/usb/em28xx/em28xx-core.c:1122
>  em28xx_usb_disconnect+0xd7/0x130 drivers/media/usb/em28xx/em28xx-cards.c:3763
>  usb_unbind_interface+0x1b6/0x950 drivers/usb/core/driver.c:423
>  __device_release_driver drivers/base/dd.c:870
>  device_release_driver_internal+0x563/0x630 drivers/base/dd.c:903
>  device_release_driver+0x1e/0x30 drivers/base/dd.c:928
>  bus_remove_device+0x2fc/0x4b0 drivers/base/bus.c:565
>  device_del+0x39f/0xa70 drivers/base/core.c:1984
>  usb_disable_device+0x223/0x710 drivers/usb/core/message.c:1205
>  usb_disconnect+0x285/0x7f0 drivers/usb/core/hub.c:2205
>  hub_port_connect drivers/usb/core/hub.c:4851
>  hub_port_connect_change drivers/usb/core/hub.c:5106
>  port_event drivers/usb/core/hub.c:5212
>  hub_event_impl+0x10f0/0x3440 drivers/usb/core/hub.c:5324
>  hub_event+0x38/0x50 drivers/usb/core/hub.c:5222
>  process_one_work+0x944/0x15f0 kernel/workqueue.c:2112
>  worker_thread+0xef/0x10d0 kernel/workqueue.c:2246
>  kthread+0x367/0x420 kernel/kthread.c:238
>  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:437
> 

this looks similar to the oops fixed by this patch:

https://patchwork.linuxtv.org/patch/45219/

Could you try if it fixes your case also?

Regards
Matthias