Re: [PATCH v2] media: dvb-usb: Fix unexpected infinite loop in dvb_usb_read_remote_control()
From: Zheng Yejian
Date: Mon May 27 2024 - 04:27:24 EST
On 2024/5/3 19:51, Sean Young wrote:
On Tue, Apr 30, 2024 at 06:41:37PM +0800, 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, 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@xxxxxxxxxx>
---
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@xxxxxxxxxxxxxx/
Link: https://lore.kernel.org/all/ZjC7rXU7ViaH60_S@xxxxxxxxxxxxxx/
- Add Fixes tag.
v1:
- Link: https://lore.kernel.org/all/20240412135256.1546051-1-zhengyejian1@xxxxxxxxxx/
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;
This results in the following warning:
drivers/media/usb/dvb-usb/dvb-usb-init.c:133:9: warning: 'adap' may be used uninitialized [-Wmaybe-uninitialized]
I think these tests should be moved to the top of the function, so no cleanup
is required.
Hi, Sean,
I have fixed the warning in v3: https://lore.kernel.org/all/20240509124414.1392304-1-zhengyejian1@xxxxxxxxxx/,
would you mind taking a look at it ?
I introduce a new funciton dvb_usb_clear_halt() to clear sndbulkpipe and rcvbulkpipe,
dvb_usb_check_bulk_endpoint() only do pipe type check and is moved to the top of
the function.
--
Thanks,
Zheng Yejian
Sean