[Bug 212995] New: A possible divide by zero in qh_urb_transaction

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=212995

            Bug ID: 212995
           Summary: A possible divide by zero in qh_urb_transaction
           Product: Drivers
           Version: 2.5
    Kernel Version: 5.12.2
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: USB
          Assignee: drivers_usb@kernel-bugs.kernel.org
          Reporter: yguoaz@gmail.com
        Regression: No

In the file drivers/usb/host/ehci-q.c, the function qh_urb_transaction has the
following code (link to the code location:
https://github.com/torvalds/linux/blob/dd860052c99b1e088352bdd4fb7aef46f8d2ef47/drivers/usb/host/ehci-q.c#L715):

maxpacket = usb_maxpacket(urb->dev, urb->pipe, !is_input);
...
if (usb_pipeout(urb->pipe) && (urb->transfer_flags & URB_ZERO_PACKET)
                           && !(urb->transfer_buffer_length % maxpacket))

However, the function usb_maxpacket may retun 0, leading to a possible divide
zero problem in the remainder operation:

static inline __u16
usb_maxpacket(struct usb_device *udev, int pipe, int is_out)
{
        struct usb_host_endpoint        *ep;
        ...
        if (!ep)
                return 0;
        ...
}

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