linux-kernel - [PATCH] drivers/video: Bad error test before a dereference

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Date:	Fri, 26 Sep 2008 15:53:44 +0200
From:	Julien Brunel <brunel@...u.dk>
To:	nicolas.ferre@...el.com, adaplas@...il.com,
	linux-fbdev-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] drivers/video: Bad error test before a dereference

The error test that follows the call to backlight_device_register
semms not to concern the right variable.

A simplified version of the semantic match that finds this problem is
as follows: 
(http://www.emn.fr/x-info/coccinelle/)
// <smpl>
@def0@
expression x;
position p0;
@@
x@p0 = backlight_device_register(...)

@protected@
expression def0.x,E;
position def0.p0;
position p;
statement S;
@@
x@p0
... when != x = E
if (!IS_ERR(x) && ...) {<... x@p ...>} else S

@unprotected@
expression def0.x;
identifier fld;
position def0.p0;
position p != protected.p;
@@
x@p0
... when != x = E
* x@p->fld
// </smpl>

Signed-off-by: Julien Brunel <brunel@...u.dk>
Signed-off-by: Julia Lawall <julia@...u.dk>

---
 drivers/video/atmel_lcdfb.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff -u -p a/drivers/video/atmel_lcdfb.c b/drivers/video/atmel_lcdfb.c
--- a/drivers/video/atmel_lcdfb.c
+++ b/drivers/video/atmel_lcdfb.c
@@ -132,7 +132,7 @@ static void init_backlight(struct atmel_
 
 	bl = backlight_device_register("backlight", &sinfo->pdev->dev,
 			sinfo, &atmel_lcdc_bl_ops);
-	if (IS_ERR(sinfo->backlight)) {
+	if (IS_ERR(bl)) {
 		dev_err(&sinfo->pdev->dev, "error %ld on backlight register\n",
 				PTR_ERR(bl));
 		return;
--
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