diff mbox

[3/10] video: use safer test on the result of find_first_zero_bit

Message ID 1401872880-23685-4-git-send-email-Julia.Lawall@lip6.fr (mailing list archive)
State New, archived
Headers show

Commit Message

Julia Lawall June 4, 2014, 9:07 a.m. UTC 
From: Julia Lawall <Julia.Lawall@lip6.fr>

Find_first_zero_bit considers BITS_PER_LONG bits at a time, and thus may
return a larger number than the maximum position argument if that position
is not a multiple of BITS_PER_LONG.

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

// <smpl>
@@
expression e1,e2,e3;
statement S1,S2;
@@

e1 = find_first_zero_bit(e2,e3)
...
if (e1 
- ==
+ >=
  e3)
S1 else S2
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>

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


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Comments

Tomi Valkeinen June 23, 2014, 11:50 a.m. UTC | #1 
On 04/06/14 12:07, Julia Lawall wrote:
> From: Julia Lawall <Julia.Lawall@lip6.fr>
> 
> Find_first_zero_bit considers BITS_PER_LONG bits at a time, and thus may
> return a larger number than the maximum position argument if that position
> is not a multiple of BITS_PER_LONG.

Thanks, queued for 3.17.

 Tomi
Julia Lawall June 23, 2014, 2:12 p.m. UTC | #2 
On Mon, 23 Jun 2014, Tomi Valkeinen wrote:

> On 04/06/14 12:07, Julia Lawall wrote:
> > From: Julia Lawall <Julia.Lawall@lip6.fr>
> >
> > Find_first_zero_bit considers BITS_PER_LONG bits at a time, and thus may
> > return a larger number than the maximum position argument if that position
> > is not a multiple of BITS_PER_LONG.
>
> Thanks, queued for 3.17.

No, sorry you can drop it.  It doesn't hurt anything, but it is not
necessary either.  Returning a larger number is actually not possible.

julia
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Tomi Valkeinen June 24, 2014, 7:56 a.m. UTC | #3 
On 23/06/14 17:12, Julia Lawall wrote:
> On Mon, 23 Jun 2014, Tomi Valkeinen wrote:
> 
>> On 04/06/14 12:07, Julia Lawall wrote:
>>> From: Julia Lawall <Julia.Lawall@lip6.fr>
>>>
>>> Find_first_zero_bit considers BITS_PER_LONG bits at a time, and thus may
>>> return a larger number than the maximum position argument if that position
>>> is not a multiple of BITS_PER_LONG.
>>
>> Thanks, queued for 3.17.
> 
> No, sorry you can drop it.  It doesn't hurt anything, but it is not
> necessary either.  Returning a larger number is actually not possible.

Ok, dropped.

 Tomi
diff mbox

Patch

diff -u -p a/drivers/video/fbdev/sh_mobile_meram.c b/drivers/video/fbdev/sh_mobile_meram.c
--- a/drivers/video/fbdev/sh_mobile_meram.c
+++ b/drivers/video/fbdev/sh_mobile_meram.c
@@ -222,7 +222,7 @@  static int meram_plane_alloc(struct sh_m
 	unsigned long idx;
 
 	idx = find_first_zero_bit(&priv->used_icb, 28);
-	if (idx == 28)
+	if (idx >= 28)
 		return -ENOMEM;
 	plane->cache = &priv->icbs[idx];