USB: fix the usbfs flag sanitization for control transfers

Commit 7a68d9fb ("USB: usbdevfs: sanitize flags more") checks the
transfer flags for URBs submitted from userspace via usbfs.  However,
the check for whether the USBDEVFS_URB_SHORT_NOT_OK flag should be
allowed for a control transfer was added in the wrong place, before
the code has properly determined the direction of the control
transfer.  (Control transfers are special because for them, the
direction is set by the bRequestType byte of the Setup packet rather
than direction bit of the endpoint address.)

This patch moves code which sets up the allow_short flag for control
transfers down after is_in has been set to the correct value.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-and-tested-by: syzbot+24a30223a4b609bb802e@syzkaller.appspotmail.com
Fixes: 7a68d9fb ("USB: usbdevfs: sanitize flags more")
CC: Oliver Neukum <oneukum@suse.com>
CC: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/devio.c

@@ -1474,8 +1474,6 @@ static int proc_do_submiturb(struct usb_dev_state *ps, struct usbdevfs_urb *uurb
 	u = 0;
 	switch (uurb->type) {
 	case USBDEVFS_URB_TYPE_CONTROL:
-		if (is_in)
-			allow_short = true;
 		if (!usb_endpoint_xfer_control(&ep->desc))
 			return -EINVAL;
 		/* min 8 byte setup packet */
@@ -1505,6 +1503,8 @@ static int proc_do_submiturb(struct usb_dev_state *ps, struct usbdevfs_urb *uurb
 			is_in = 0;
 			uurb->endpoint &= ~USB_DIR_IN;
 		}
+		if (is_in)
+			allow_short = true;
 		snoop(&ps->dev->dev, "control urb: bRequestType=%02x "
 			"bRequest=%02x wValue=%04x "
 			"wIndex=%04x wLength=%04x\n",