linux-kernel - [PATCH 1/3] drivers/media/video/em28xx: Remove potential NULL dereference

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Message-Id: <1282888640-27042-2-git-send-email-julia@diku.dk>
Date:	Fri, 27 Aug 2010 07:57:18 +0200
From:	Julia Lawall <julia@...u.dk>
To:	Mauro Carvalho Chehab <mchehab@...radead.org>
Cc:	kernel-janitors@...r.kernel.org, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] drivers/media/video/em28xx: Remove potential NULL dereference

If the NULL test is necessary, the initialization involving a dereference of
the tested value should be moved after the NULL test.

The sematic patch that fixes this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
type T;
expression E;
identifier i,fld;
statement S;
@@

- T i = E->fld;
+ T i;
  ... when != E
      when != i
  if (E == NULL) S
+ i = E->fld;
// </smpl>

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

---
 drivers/media/video/em28xx/em28xx-video.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/media/video/em28xx/em28xx-video.c b/drivers/media/video/em28xx/em28xx-video.c
index 7b9ec6e..95a4b60 100644
--- a/drivers/media/video/em28xx/em28xx-video.c
+++ b/drivers/media/video/em28xx/em28xx-video.c
@@ -277,12 +277,13 @@ static void em28xx_copy_vbi(struct em28xx *dev,
 {
 	void *startwrite, *startread;
 	int  offset;
-	int bytesperline = dev->vbi_width;
+	int bytesperline;
 
 	if (dev == NULL) {
 		em28xx_isocdbg("dev is null\n");
 		return;
 	}
+	bytesperline = dev->vbi_width;
 
 	if (dma_q == NULL) {
 		em28xx_isocdbg("dma_q is null\n");

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