linux-kernel - [PATCH 3/3] [media] gspca_kinect: cast sizeof to int for comparison

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Date:   Sun,  1 Jul 2018 19:32:05 +0200
From:   Julia Lawall <Julia.Lawall@...6.fr>
To:     Hans Verkuil <hverkuil@...all.nl>, joe@...ches.com,
        Chengguang Xu <cgxu519@....com>
Cc:     kernel-janitors@...r.kernel.org,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] [media] gspca_kinect: 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.  kinect_read returns the result of
usb_control_msg, which can return a negtive 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/media/usb/gspca/kinect.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/usb/gspca/kinect.c b/drivers/media/usb/gspca/kinect.c
index 0cfdf8a..f993f62 100644
--- a/drivers/media/usb/gspca/kinect.c
+++ b/drivers/media/usb/gspca/kinect.c
@@ -163,7 +163,7 @@ static int send_cmd(struct gspca_dev *gspca_dev, uint16_t cmd, void *cmdbuf,
 		actual_len = kinect_read(udev, ibuf, 0x200);
 	} while (actual_len == 0);
 	gspca_dbg(gspca_dev, D_USBO, "Control reply: %d\n", actual_len);
-	if (actual_len < sizeof(*rhdr)) {
+	if (actual_len < (int)sizeof(*rhdr)) {
 		pr_err("send_cmd: Input control transfer failed (%d)\n",
 		       actual_len);
 		return actual_len < 0 ? actual_len : -EREMOTEIO;