linux-kernel - [PATCH v2] media: dvb-usb: Fix unexpected infinite loop in dvb_usb_read_remote

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Message-ID: <20240430104137.1014471-1-zhengyejian1@huawei.com>
Date: Tue, 30 Apr 2024 18:41:37 +0800
From: Zheng Yejian <zhengyejian1@...wei.com>
To: <sean@...s.org>, <mchehab@...nel.org>
CC: <linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>,
	<zhengyejian1@...wei.com>
Subject: [PATCH v2] media: dvb-usb: Fix unexpected infinite loop in dvb_usb_read_remote_control()

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, we need to add endpoint check for 'generic_bulk_ctrl_endpoint'.
And as Sean suggested, the same check and clear halts should be done for
'generic_bulk_ctrl_endpoint_response'. So introduce
dvb_usb_check_bulk_endpoint() to do it for both of them.

Fixes: 4d43e13f723e ("V4L/DVB (4643): Multi-input patch for DVB-USB device")
Signed-off-by: Zheng Yejian <zhengyejian1@...wei.com>
---
 drivers/media/usb/dvb-usb/dvb-usb-init.c | 27 ++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

v2:
 - As Sean suggested, check endpoint and clear halt for both
   'generic_bulk_ctrl_endpoint' and 'generic_bulk_ctrl_endpoint_response'
   with the new introduced dvb_usb_check_bulk_endpoint();
   Link: https://lore.kernel.org/all/ZjCl97Ww6NrzJQCB@gofer.mess.org/
   Link: https://lore.kernel.org/all/ZjC7rXU7ViaH60_S@gofer.mess.org/

 - Add Fixes tag.

v1:
 - Link: https://lore.kernel.org/all/20240412135256.1546051-1-zhengyejian1@huawei.com/

diff --git a/drivers/media/usb/dvb-usb/dvb-usb-init.c b/drivers/media/usb/dvb-usb/dvb-usb-init.c
index fbf58012becd..7eb321bab84f 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_check_bulk_endpoint(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_check_bulk_endpoint(d, d->props.generic_bulk_ctrl_endpoint);
+	if (ret)
+		goto frontend_init_err;
+	ret = dvb_usb_check_bulk_endpoint(d, d->props.generic_bulk_ctrl_endpoint_response);
+	if (ret)
+		goto frontend_init_err;
 
 	return 0;
 
-- 
2.25.1