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From: Zheng Yejian <zhengyejian1@huawei.com>
To: <mchehab@kernel.org>
CC: <linux-media@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<zhengyejian1@huawei.com>
Subject: [PATCH] media: dvb-usb: Fix unexpected infinite loop in dvb_usb_read_remote_control()
Date: Fri, 12 Apr 2024 21:52:56 +0800
Message-ID: <20240412135256.1546051-1-zhengyejian1@huawei.com>
Precedence: bulk
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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 ? :)

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));
 	}
-- 
2.25.1