linux-kernel - [PATCH 2/3] usb: wusbcore: security: cast sizeof to int for comparison

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Message-Id: <1530466325-1678-3-git-send-email-Julia.Lawall@lip6.fr>
Date:   Sun,  1 Jul 2018 19:32:04 +0200
From:   Julia Lawall <Julia.Lawall@...6.fr>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>, joe@...ches.com,
        Chengguang Xu <cgxu519@....com>
Cc:     kernel-janitors@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] usb: wusbcore: security: cast sizeof to int for comparison

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>

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

diff --git a/drivers/usb/wusbcore/security.c b/drivers/usb/wusbcore/security.c
index 33d2f5d..14ac8c9 100644
--- a/drivers/usb/wusbcore/security.c
+++ b/drivers/usb/wusbcore/security.c
@@ -217,7 +217,7 @@ int wusb_dev_sec_add(struct wusbhc *wusbhc,
 
 	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;