linux-kernel - [PATCH 1/1] usb: usbip: vudc: fix left shift overflow

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Date:   Tue, 23 Aug 2016 17:13:29 +0200
From:   Nicolas Iooss <nicolas.iooss_linux@....org>
To:     Valentina Manea <valentina.manea.m@...il.com>,
        Shuah Khan <shuahkh@....samsung.com>,
        Shuah Khan <shuah@...nel.org>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Nicolas Iooss <nicolas.iooss_linux@....org>
Subject: [PATCH 1/1] usb: usbip: vudc: fix left shift overflow

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

diff --git a/drivers/usb/usbip/vudc_rx.c b/drivers/usb/usbip/vudc_rx.c
index 344bd9473475..e429b59f6f8a 100644
--- 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 *udc,
 	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);
-- 
2.9.3