Re: [PATCH] media: dvb-usb: Fix unexpected infinite loop in dvb_usb_read_remote_control()

[Zheng Yejian <zhengyejian1@huawei.com>]

On 2024/4/30 16:04, Sean Young wrote:
> On Mon, Apr 29, 2024 at 07:24:21PM +0800, Zheng Yejian wrote:
>> On 2024/4/12 21:52, Zheng Yejian wrote:
>>> Infinite log printing occurs during fuzz test:
>>>
>>>     rc rc1: DViCO FusionHDTV DVB-T USB (LGZ201) as ...
>>>     ...
>>>     dvb-usb: schedule remote query interval to 100 msecs.
>>>     dvb-usb: DViCO FusionHDTV DVB-T USB (LGZ201) successfully initialized ...
>>>     dvb-usb: bulk message failed: -22 (1/0)
>>>     dvb-usb: bulk message failed: -22 (1/0)
>>>     dvb-usb: bulk message failed: -22 (1/0)
>>>     ...
>>>     dvb-usb: bulk message failed: -22 (1/0)
>>>
>>> Looking into the codes, there is a loop in dvb_usb_read_remote_control(),
>>> that is in rc_core_dvb_usb_remote_init() create a work that will call
>>> dvb_usb_read_remote_control(), and this work will reschedule itself at
>>> 'rc_interval' intervals to recursively call dvb_usb_read_remote_control(),
>>> see following code snippet:
>>>
>>>     rc_core_dvb_usb_remote_init() {
>>>       ...
>>>       INIT_DELAYED_WORK(&d->rc_query_work, dvb_usb_read_remote_control);
>>>       schedule_delayed_work(&d->rc_query_work,
>>>                             msecs_to_jiffies(rc_interval));
>>>       ...
>>>     }
>>>
>>>     dvb_usb_read_remote_control() {
>>>       ...
>>>       err = d->props.rc.core.rc_query(d);
>>>       if (err)
>>>         err(...)  // Did not return even if query failed
>>>       schedule_delayed_work(&d->rc_query_work,
>>>                             msecs_to_jiffies(rc_interval));
>>>     }
>>>
>>> When the infinite log printing occurs, the query callback
>>> 'd->props.rc.core.rc_query' is cxusb_rc_query(). And the log is due to
>>> the failure of finding a valid 'generic_bulk_ctrl_endpoint'
>>> in usb_bulk_msg(), see following code snippet:
>>>
>>>     cxusb_rc_query() {
>>>       cxusb_ctrl_msg() {
>>>         dvb_usb_generic_rw() {
>>>           ret = usb_bulk_msg(d->udev, usb_sndbulkpipe(d->udev,
>>>                              d->props.generic_bulk_ctrl_endpoint),...);
>>>           if (ret)
>>>             err("bulk message failed: %d (%d/%d)",ret,wlen,actlen);
>>>             ...
>>>         }
>>>     ...
>>>     }
>>>
>>> By analyzing the corresponding USB descriptor, it shows that the
>>> bNumEndpoints is 0 in its interface descriptor, but
>>> the 'generic_bulk_ctrl_endpoint' is 1, that means user don't configure
>>> a valid endpoint for 'generic_bulk_ctrl_endpoint', therefore this
>>> 'invalid' USB device should be rejected before it calls into
>>> dvb_usb_read_remote_control().
>>>
>>> To fix it, iiuc, we can add endpoint check in dvb_usb_adapter_init().
>>>
>>> Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
>>> ---
>>>    drivers/media/usb/dvb-usb/dvb-usb-init.c | 8 ++++++++
>>>    1 file changed, 8 insertions(+)
>>>
>>> Hi, I'm not very familiar with USB driver, and I'm not sure the
>>> type check is appropriate or not here. Would be any device properties
>>> that allow 'generic_bulk_ctrl_endpoint' not being configured, or would
>>> it be configured late after init ? :)
>>>
>>
>> Kindly ping :)
>> Hi, Mauro, would you mind taking a look at this code ?
>>
>> --
>> Thanks,
>> Zheng Yejian
>>
>>> diff --git a/drivers/media/usb/dvb-usb/dvb-usb-init.c b/drivers/media/usb/dvb-usb/dvb-usb-init.c
>>> index fbf58012becd..48e7b9fb93dd 100644
>>> --- a/drivers/media/usb/dvb-usb/dvb-usb-init.c
>>> +++ b/drivers/media/usb/dvb-usb/dvb-usb-init.c
>>> @@ -104,6 +104,14 @@ static int dvb_usb_adapter_init(struct dvb_usb_device *d, short *adapter_nrs)
>>>    	 * sometimes a timeout occurs, this helps
>>>    	 */
>>>    	if (d->props.generic_bulk_ctrl_endpoint != 0) {
>>> +		ret = usb_pipe_type_check(d->udev, usb_sndbulkpipe(d->udev,
>>> +					  d->props.generic_bulk_ctrl_endpoint));
>>> +		if (ret)
>>> +			goto frontend_init_err;
>>> +		ret = usb_pipe_type_check(d->udev, usb_rcvbulkpipe(d->udev,
>>> +					  d->props.generic_bulk_ctrl_endpoint));
>>> +		if (ret)
>>> +			goto frontend_init_err;
>>>    		usb_clear_halt(d->udev, usb_sndbulkpipe(d->udev, d->props.generic_bulk_ctrl_endpoint));
>>>    		usb_clear_halt(d->udev, usb_rcvbulkpipe(d->udev, d->props.generic_bulk_ctrl_endpoint));
>>>    	}
>>
> 
> Thank you for your patch.
> 
> I think your change looks good. The only comment I have is that the same
> check should be done for generic_bulk_ctrl_endpoint_response as well; the
> usb_clear_halt() should be done as well, I think.
> 

Thanks for your suggestion!
Do you mean the following change? If it is ok, I'll send a v2!

diff --git a/drivers/media/usb/dvb-usb/dvb-usb-init.c b/drivers/media/usb/dvb-usb/dvb-usb-init.c
index fbf58012becd..2a8395d6373c 100644
--- a/drivers/media/usb/dvb-usb/dvb-usb-init.c
+++ b/drivers/media/usb/dvb-usb/dvb-usb-init.c
@@ -23,6 +23,23 @@ static int dvb_usb_force_pid_filter_usage;
  module_param_named(force_pid_filter_usage, dvb_usb_force_pid_filter_usage, int, 0444);
  MODULE_PARM_DESC(force_pid_filter_usage, "force all dvb-usb-devices to use a PID filter, if any (default: 0).");

+static int dvb_usb_clear_halt(struct dvb_usb_device *d, u8 endpoint)
+{
+       if (endpoint) {
+               int ret;
+
+               ret = usb_pipe_type_check(d->udev, usb_sndbulkpipe(d->udev, endpoint));
+               if (ret)
+                       return ret;
+               ret = usb_pipe_type_check(d->udev, usb_rcvbulkpipe(d->udev, endpoint));
+               if (ret)
+                       return ret;
+               usb_clear_halt(d->udev, usb_sndbulkpipe(d->udev, endpoint));
+               usb_clear_halt(d->udev, usb_rcvbulkpipe(d->udev, endpoint));
+       }
+       return 0;
+}
+
  static int dvb_usb_adapter_init(struct dvb_usb_device *d, short *adapter_nrs)
  {
         struct dvb_usb_adapter *adap;
@@ -103,10 +120,12 @@ static int dvb_usb_adapter_init(struct dvb_usb_device *d, short *adapter_nrs)
          * when reloading the driver w/o replugging the device
          * sometimes a timeout occurs, this helps
          */
-       if (d->props.generic_bulk_ctrl_endpoint != 0) {
-               usb_clear_halt(d->udev, usb_sndbulkpipe(d->udev, d->props.generic_bulk_ctrl_endpoint));
-               usb_clear_halt(d->udev, usb_rcvbulkpipe(d->udev, d->props.generic_bulk_ctrl_endpoint));
-       }
+       ret = dvb_usb_clear_halt(d, d->props.generic_bulk_ctrl_endpoint);
+       if (ret)
+               goto frontend_init_err;
+       ret = dvb_usb_clear_halt(d, d->props.generic_bulk_ctrl_endpoint_response);
+       if (ret)
+               goto frontend_init_err;

         return 0;

--
Thanks,
Zheng Yejian

> Thanks
> 
> Sean