linux-kernel - [PATCH 4.8 05/10] usb: usbip: vudc: fix left shift overflow

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Date:   Thu,  6 Oct 2016 10:18:28 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nicolas Iooss <nicolas.iooss_linux@....org>
Subject: [PATCH 4.8 05/10] usb: usbip: vudc: fix left shift overflow

4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicolas Iooss <nicolas.iooss_linux@....org>

commit 238b7bd91b16d5a08326f858db42229b212e53d8 upstream.

In v_recv_cmd_submit(), urb_p->urb->pipe has the type unsigned int
(which is 32-bit long on x86_64) but 11<<30 results in a 34-bit integer.
Therefore the 2 leading bits are truncated and

    urb_p->urb->pipe &= ~(11 << 30);

has the same meaning as

    urb_p->urb->pipe &= ~(3 << 30);

This second statement seems to be how the code was intended to be
written, as PIPE_ constants have values between 0 and 3.

The overflow has been detected with a clang warning:

    drivers/usb/usbip/vudc_rx.c:145:27: warning: signed shift result
    (0x2C0000000) requires 35 bits to represent, but 'int' only has 32
    bits [-Wshift-overflow]
            urb_p->urb->pipe &= ~(11 << 30);
                                  ~~ ^  ~~

Fixes: 79c02cb1fd5c ("usbip: vudc: Add vudc_rx")
Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@....org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/usb/usbip/vudc_rx.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/usb/usbip/vudc_rx.c
+++ b/drivers/usb/usbip/vudc_rx.c
@@ -142,7 +142,7 @@ static int v_recv_cmd_submit(struct vudc
 	urb_p->urb->status = -EINPROGRESS;
 
 	/* FIXME: more pipe setup to please usbip_common */
-	urb_p->urb->pipe &= ~(11 << 30);
+	urb_p->urb->pipe &= ~(3 << 30);
 	switch (urb_p->ep->type) {
 	case USB_ENDPOINT_XFER_BULK:
 		urb_p->urb->pipe |= (PIPE_BULK << 30);