[ Upstream commit8491e73a52] If the agilent usb dongle is disconnected subsequent calls to the driver cause a NULL dereference Oops as the bus_interface is set to NULL on disconnect. This problem was introduced by setting usb_dev from the bus_interface for dev_xxx messages. Previously bus_interface was checked for NULL only in the functions directly calling usb_fill_bulk_urb or usb_control_msg. Check for valid bus_interface on all interface entry points and return -ENODEV if it is NULL. Fixes:fbae7090f3("staging: gpib: Update messaging and usb_device refs in agilent_usb") Cc: stable <stable@kernel.org> Signed-off-by: Dave Penkler <dpenkler@gmail.com> Link: https://lore.kernel.org/r/20250222204515.5104-1-dpenkler@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>