Re: [PATCH v2] media:dvb-frontends:Remove dvb_pll_devcount and id module parameters.

[Vandana BN <bnvandana@gmail.com>]

On 01/08/19 10:39 AM, Sean Young wrote:
> On Wed, Jul 24, 2019 at 06:36:35AM +0100, Sean Young wrote:
>> On Sat, Jul 20, 2019 at 11:43:02AM +0530, Vandana BN wrote:
>>> Syzbot reported global-out-of-bounds Read in dvb_pll_attach, while
>>> accessing id[dvb_pll_devcount], because dvb_pll_devcount was 65,
>>> that is more than size of 'id' which is DVB_PLL_MAX(64).
>>>
>>> Fix would be to check if DVB_PLL_MAX devices are attached and if so return
>>> NULL from dvb_pll_attach(). But this will put a limit on the number of
>>> devices that can be attached.
>>> Also dvb_pll_devcount and "id" module parameter are used for debugging
>>> purpose to override/force PLL type.
>>> So this patch removes these module parameters.
>>>
>>> Reported-by: syz...@syzkaller.appspotmail.com
>>>
>>> usb 1-1: dvb_usb_v2: will pass the complete MPEG2 transport stream to the
>>> software demuxer
>>> dvbdev: DVB: registering new adapter (774 Friio White ISDB-T USB2.0)
>>> usb 1-1: media controller created
>>> dvbdev: dvb_create_media_entity: media entity 'dvb-demux' registered.
>>> tc90522 0-0018: Toshiba TC90522 attached.
>>> usb 1-1: DVB: registering adapter 0 frontend 0 (Toshiba TC90522 ISDB-T
>>> module)...
>>> dvbdev: dvb_create_media_entity: media entity 'Toshiba TC90522 ISDB-T
>>> module' registered.
>>> ==================================================================
>>> BUG: KASAN: global-out-of-bounds in dvb_pll_attach+0x6c5/0x830
>>> drivers/media/dvb-frontends/dvb-pll.c:798
>>> Read of size 4 at addr ffffffff89c9e5e0 by task kworker/0:1/12
>>>
>>> CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.2.0-rc6+ #13
>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>>> Google 01/01/2011
>>> Workqueue: usb_hub_wq hub_event
>>> Call Trace:
>>>   __dump_stack lib/dump_stack.c:77 [inline]
>>>   dump_stack+0xca/0x13e lib/dump_stack.c:113
>>>   print_address_description+0x67/0x231 mm/kasan/report.c:188
>>>   __kasan_report.cold+0x1a/0x32 mm/kasan/report.c:317
>>>   kasan_report+0xe/0x20 mm/kasan/common.c:614
>>>   dvb_pll_attach+0x6c5/0x830 drivers/media/dvb-frontends/dvb-pll.c:798
>>>   dvb_pll_probe+0xfe/0x174 drivers/media/dvb-frontends/dvb-pll.c:877
>>>   i2c_device_probe+0x790/0xaa0 drivers/i2c/i2c-core-base.c:389
>>>   really_probe+0x281/0x660 drivers/base/dd.c:509
>>>   driver_probe_device+0x104/0x210 drivers/base/dd.c:670
>>>   __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:777
>>>   bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454
>>>   __device_attach+0x217/0x360 drivers/base/dd.c:843
>>>   bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
>>>   device_add+0xae6/0x16f0 drivers/base/core.c:2111
>>>   i2c_new_client_device+0x5b3/0xc40 drivers/i2c/i2c-core-base.c:778
>>>   i2c_new_device+0x19/0x50 drivers/i2c/i2c-core-base.c:821
>>>   dvb_module_probe+0xf9/0x220 drivers/media/dvb-core/dvbdev.c:985
>>>   friio_tuner_attach+0x125/0x1d0 drivers/media/usb/dvb-usb-v2/gl861.c:536
>>>   dvb_usbv2_adapter_frontend_init
>>> drivers/media/usb/dvb-usb-v2/dvb_usb_core.c:675 [inline]
>>>   dvb_usbv2_adapter_init drivers/media/usb/dvb-usb-v2/dvb_usb_core.c:804
>>> [inline]
>>>   dvb_usbv2_init drivers/media/usb/dvb-usb-v2/dvb_usb_core.c:865 [inline]
>>>   dvb_usbv2_probe.cold+0x24dc/0x255d
>>> drivers/media/usb/dvb-usb-v2/dvb_usb_core.c:980
>>>   usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
>>>   really_probe+0x281/0x660 drivers/base/dd.c:509
>>>   driver_probe_device+0x104/0x210 drivers/base/dd.c:670
>>>   __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:777
>>>   bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454
>>>   __device_attach+0x217/0x360 drivers/base/dd.c:843
>>>   bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
>>>   device_add+0xae6/0x16f0 drivers/base/core.c:2111
>>>   usb_set_configuration+0xdf6/0x1670 drivers/usb/core/message.c:2023
>>>   generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
>>>   usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
>>>   really_probe+0x281/0x660 drivers/base/dd.c:509
>>>   driver_probe_device+0x104/0x210 drivers/base/dd.c:670
>>>   __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:777
>>>   bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454
>>>   __device_attach+0x217/0x360 drivers/base/dd.c:843
>>>   bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
>>>   device_add+0xae6/0x16f0 drivers/base/core.c:2111
>>>   usb_new_device.cold+0x8c1/0x1016 drivers/usb/core/hub.c:2534
>>>   hub_port_connect drivers/usb/core/hub.c:5089 [inline]
>>>   hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
>>>   port_event drivers/usb/core/hub.c:5350 [inline]
>>>   hub_event+0x1ada/0x3590 drivers/usb/core/hub.c:5432
>>>   process_one_work+0x905/0x1570 kernel/workqueue.c:2269
>>>   process_scheduled_works kernel/workqueue.c:2331 [inline]
>>>   worker_thread+0x7ab/0xe20 kernel/workqueue.c:2417
>>>   kthread+0x30b/0x410 kernel/kthread.c:255
>>>   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
>>>
>>> The buggy address belongs to the variable:
>>>   id+0x100/0x120
>>>
>>> Memory state around the buggy address:
>>>   ffffffff89c9e480: fa fa fa fa 00 00 fa fa fa fa fa fa 00 00 00 00
>>>   ffffffff89c9e500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>>> ffffffff89c9e580: 00 00 00 00 00 00 00 00 00 00 00 00 fa fa fa fa
>>>                                                         ^
>>>   ffffffff89c9e600: 04 fa fa fa fa fa fa fa 04 fa fa fa fa fa fa fa
>>>   ffffffff89c9e680: 04 fa fa fa fa fa fa fa 04 fa fa fa fa fa fa fa
>>> ==================================================================
>>>
>>> Signed-off-by: Vandana BN <bnvandana@gmail.com>
>>> ---
>>>  drivers/media/dvb-frontends/dvb-pll.c | 19 +++----------------
>>>  1 file changed, 3 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/drivers/media/dvb-frontends/dvb-pll.c b/drivers/media/dvb-frontends/dvb-pll.c
>>> index ba0c49107bd2..c3a04751e9cf 100644
>>> --- a/drivers/media/dvb-frontends/dvb-pll.c
>>> +++ b/drivers/media/dvb-frontends/dvb-pll.c
>>> @@ -33,19 +33,11 @@ struct dvb_pll_priv {
>>>  	u32 bandwidth;
>>>  };
>>>
>>> -#define DVB_PLL_MAX 64
>>> -
>>> -static unsigned int dvb_pll_devcount;
>>>
>>>  static int debug;
>>>  module_param(debug, int, 0644);
>>>  MODULE_PARM_DESC(debug, "enable verbose debug messages");
>>>
>>> -static unsigned int id[DVB_PLL_MAX] =
>>> -	{ [ 0 ... (DVB_PLL_MAX-1) ] = DVB_PLL_UNDEFINED };
>>> -module_param_array(id, int, NULL, 0644);
>>> -MODULE_PARM_DESC(id, "force pll id to use (DEBUG ONLY)");
>>> -
>> Mike, you introduced this module parameter in:
>>
>> commit 05a4611b5d71ad6f968fdeef092c24914570898b
>> Author:     Michael Krufky <mkrufky@linuxtv.org>
>> AuthorDate: Fri Sep 7 18:19:57 2007 -0300
>>
>>     V4L/DVB (6228): dvb-pll: add module option to specify rf input
>>     
>>     Add a module option to dvb-pll, called "input" to specify which rf
>>     input to use on devices with multiple rf inputs.  If the module option
>>     is not specified, then the driver will autoselect the rf input, as per
>>     previous behavior.
>>     
>>     Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
>>     Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
>>
>> What was your motivation?
> dvb_pll_devcount only ever gets increased, so this only works for the
> first time a driver is loaded; after a usb replug or rmmod this does
> not work anymore since the dvb_pll_devcount will have moved on to the
> next entry. Considering it is broken maybe it should just be removed;
> also we have no answer from mkrufky yet.
>
> If this functionality is useful, then it should be implemented with
> an DEFINE_IDA() and ida_simpla_get(), but I'm not sure it's worth it
> when the functionality is probably unused. If it was used, someone
> would have noticed it was broken.

Thanks Sean,

I Will send updated patch addressing your review comments.

Regards,

Vandana.

>
> Sean