usb_wwan_close() drains the delayed write urbs with
usb_get_from_anchor(), which returns the urb with a new reference
taken. The loop only clears the busy flag of the urb and never drops
that reference, so each drained urb keeps one reference forever and
the urb object is not freed when usb_wwan_port_remove() later drops
the port's own reference.

Drop the reference with usb_put_urb() once the urb has been found in
the out_urb array by unbusy_queued_urb(), leaving the reference held
by the port's preallocated out_urbs array.

Fixes: 79eed03e77d4 ("USB: usb_wwan: fix urb leak at shutdown")
Cc: stable@vger.kernel.org
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
---
 drivers/usb/serial/usb_wwan.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/serial/usb_wwan.c b/drivers/usb/serial/usb_wwan.c
index e752ffa4dc62..2c46330f10da 100644
--- a/drivers/usb/serial/usb_wwan.c
+++ b/drivers/usb/serial/usb_wwan.c
@@ -403,6 +403,7 @@ void usb_wwan_close(struct usb_serial_port *port)
 		if (!urb)
 			break;
 		unbusy_queued_urb(urb, portdata);
+		usb_put_urb(urb);
 		usb_autopm_put_interface_async(serial->interface);
 	}
 
-- 
2.34.1

On Wed, Sep 16, 2026 at 04:56:08PM +0000, Wentao Liang wrote:
> usb_wwan_close() drains the delayed write urbs with
> usb_get_from_anchor(), which returns the urb with a new reference
> taken. The loop only clears the busy flag of the urb and never drops
> that reference, so each drained urb keeps one reference forever and
> the urb object is not freed when usb_wwan_port_remove() later drops
> the port's own reference.
> 
> Drop the reference with usb_put_urb() once the urb has been found in
> the out_urb array by unbusy_queued_urb(), leaving the reference held
> by the port's preallocated out_urbs array.
> 
> Fixes: 79eed03e77d4 ("USB: usb_wwan: fix urb leak at shutdown")
> Cc: stable@vger.kernel.org
> Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>

Also looks correct, but again, how was this issue found and fixed?

Johan