linux-kernel - [PATCH] drivers/s390: put NULL test before dereference

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Date:	Tue, 28 Jul 2009 19:09:59 +0200 (CEST)
From:	Julia Lawall <julia@...u.dk>
To:	linux-s390@...r.kernel.org, linux390@...ibm.com,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] drivers/s390: put NULL test before dereference

From: Julia Lawall <julia@...u.dk>

If the NULL test on block is needed, it should be before the dereference of
the base field.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@r@
expression E1,E2;
identifier fld;
statement S1,S2;
@@

E1 = E2->fld;
(
if (E1 == NULL) S1 else S2
|
*if (E2 == NULL) S1 else S2
)
// </smpl>

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

---
 drivers/s390/block/dasd.c           |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index 001af66..e109da4 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -2133,9 +2133,9 @@ static int dasd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
 	struct dasd_device *base;
 
 	block = bdev->bd_disk->private_data;
-	base = block->base;
 	if (!block)
 		return -ENODEV;
+	base = block->base;
 
 	if (!base->discipline ||
 	    !base->discipline->fill_geometry)
--
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