arun c wrote:
On Mon, Jul 20, 2009 at 1:31 PM, Adrian Hunter<adrian.hunter@xxxxxxxxx> wrote:
Julia Lawall wrote:
From: Julia Lawall <julia@xxxxxxx>
If the NULL test is necessary, then the dereference should be moved below
the NULL test.
The semantic patch that makes this change is as follows:
(http://www.emn.fr/x-info/coccinelle/)
// <smpl>
@@
type T;
expression E,E1;
identifier i,fld;
statement S;
@@
- T i = E->fld;
+ T i;
... when != E=E1
when != i
BUG_ON (E == NULL||
- i
+ E->fld
== NULL || ...);
+ i = E->fld;
// </smpl>
Signed-off-by: Julia Lawall <julia@xxxxxxx>
---
drivers/mmc/host/omap.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c
index e7a331d..89281ab 100644
--- a/drivers/mmc/host/omap.c
+++ b/drivers/mmc/host/omap.c
@@ -255,11 +255,12 @@ static void mmc_omap_slot_release_work(struct
work_struct *work)
static void mmc_omap_release_slot(struct mmc_omap_slot *slot, int
clk_enabled)
{
- struct mmc_omap_host *host = slot->host;
+ struct mmc_omap_host *host;
unsigned long flags;
int i;
- BUG_ON(slot == NULL || host->mmc == NULL);
+ BUG_ON(slot == NULL || slot->host->mmc == NULL);
+ host = slot->host;
if (clk_enabled)
/* Keeps clock running for at least 8 cycles on valid freq
*/
--
If slot is NULL it will oops anyway, so the following is better IMHO:
static void mmc_omap_release_slot(struct mmc_omap_slot *slot, int
clk_enabled)
{
struct mmc_omap_host *host = slot->host;
unsigned long flags;
int i;
- BUG_ON(slot == NULL || host->mmc == NULL);
+ BUG_ON(host->mmc == NULL);
if (clk_enabled)
/* Keeps clock running for at least 8 cycles on valid freq */
--
According to http://isc.sans.org/diary.html?storyid=6820&rss "NULL check"
must be done before assigning the values. Does Julia Lawall's version
is the more correct one??
Arun
It is not a "NULL check" it is an assertion, which can be compiled out.
On some platforms BUG is implemented as a null dereference anyway
e.g. on ARM it is *(int *)0 = 0;
--
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