usbfs: Allow printer class 'get_device_id' without needing to claim the intf

For certain (HP) printers the printer device_id does not only contain a
static part identifying the printer, but it also contains a dynamic part
giving printer status, ink level, etc.

To get to this info various userspace utilities need to be able to make a
printer class 'get_device_id' request without first claiming the interface
(as that is in use for the actual printer driver).

Since the printer class 'get_device_id' request does not change interface
settings in anyway, allowing this without claiming the interface should not
cause any issues.

CC: Sanjay Kumar <sanjay.kumar14@hp.com>
CC: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 05986507b585..737e3c19967b 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -725,15 +725,15 @@ static int check_ctrlrecip(struct dev_state *ps, unsigned int requesttype,
 
         /*
          * check for the special corner case 'get_device_id' in the printer
-         * class specification, where wIndex is (interface << 8 | altsetting)
-         * instead of just interface
+         * class specification, which we always want to allow as it is used
+         * to query things like ink level, etc.
          */
         if (requesttype == 0xa1 && request == 0) {
                 alt_setting = usb_find_alt_setting(ps->dev->actconfig,
                                                    index >> 8, index & 0xff);
                 if (alt_setting
                  && alt_setting->desc.bInterfaceClass == USB_CLASS_PRINTER)
-                        index >>= 8;
+                        return 0;
         }
 
         index &= 0xff;