linux-kernel - [PATCH 4.4 020/113] usb: wusbcore: security: cast sizeof to int for comparison

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Date:   Mon,  8 Oct 2018 20:30:21 +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, Julia Lawall <Julia.Lawall@...6.fr>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.4 020/113] usb: wusbcore: security: cast sizeof to int for comparison

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

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

From: Julia Lawall <Julia.Lawall@...6.fr>

[ Upstream commit d3ac5598c5010a8999978ebbcca3b1c6188ca36b ]

Comparing an int to a size, which is unsigned, causes the int to become
unsigned, giving the wrong result.  usb_get_descriptor can return a
negative error code.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@@
int x;
expression e,e1;
identifier f;
@@

*x = f(...);
... when != x = e1
    when != if (x < 0 || ...) { ... return ...; }
*x < sizeof(e)
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/usb/wusbcore/security.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/usb/wusbcore/security.c
+++ b/drivers/usb/wusbcore/security.c
@@ -230,7 +230,7 @@ int wusb_dev_sec_add(struct wusbhc *wusb
 
 	result = usb_get_descriptor(usb_dev, USB_DT_SECURITY,
 				    0, secd, sizeof(*secd));
-	if (result < sizeof(*secd)) {
+	if (result < (int)sizeof(*secd)) {
 		dev_err(dev, "Can't read security descriptor or "
 			"not enough data: %d\n", result);
 		goto out;