USB: avoid left shift by -1
authorAlan Stern <stern@rowland.harvard.edu>
Tue, 23 Aug 2016 19:32:51 +0000 (15:32 -0400)
committerBen Hutchings <ben@decadent.org.uk>
Sun, 20 Nov 2016 01:01:34 +0000 (01:01 +0000)
commit 53e5f36fbd2453ad69a3369a1db62dc06c30a4aa upstream.

UBSAN complains about a left shift by -1 in proc_do_submiturb().  This
can occur when an URB is submitted for a bulk or control endpoint on
a high-speed device, since the code doesn't bother to check the
endpoint type; normally only interrupt or isochronous endpoints have
a nonzero bInterval value.

Aside from the fact that the operation is illegal, it shouldn't matter
because the result isn't used.  Still, in theory it could cause a
hardware exception or other problem, so we should work around it.
This patch avoids doing the left shift unless the shift amount is >= 0.

The same piece of code has another problem.  When checking the device
speed (the exponential encoding for interrupt endpoints is used only
by high-speed or faster devices), we need to look for speed >=
USB_SPEED_SUPER as well as speed == USB_SPEED HIGH.  The patch adds
this check.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Vittorio Zecca <zeccav@gmail.com>
Tested-by: Vittorio Zecca <zeccav@gmail.com>
Suggested-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
drivers/usb/core/devio.c

index ed11901..45d3007 100644 (file)
@@ -1281,11 +1281,17 @@ static int proc_do_submiturb(struct dev_state *ps, struct usbdevfs_urb *uurb,
        as->urb->setup_packet = (unsigned char *)dr;
        as->urb->start_frame = uurb->start_frame;
        as->urb->number_of_packets = uurb->number_of_packets;
-       if (uurb->type == USBDEVFS_URB_TYPE_ISO ||
-                       ps->dev->speed == USB_SPEED_HIGH)
-               as->urb->interval = 1 << min(15, ep->desc.bInterval - 1);
-       else
-               as->urb->interval = ep->desc.bInterval;
+
+       if (ep->desc.bInterval) {
+               if (uurb->type == USBDEVFS_URB_TYPE_ISO ||
+                               ps->dev->speed == USB_SPEED_HIGH ||
+                               ps->dev->speed >= USB_SPEED_SUPER)
+                       as->urb->interval = 1 <<
+                                       min(15, ep->desc.bInterval - 1);
+               else
+                       as->urb->interval = ep->desc.bInterval;
+       }
+
        as->urb->context = as;
        as->urb->complete = async_completed;
        for (totlen = u = 0; u < uurb->number_of_packets; u++) {