drivers/media/video: avoid NULL dereference
Commit Message
From: Julia Lawall <julia@diku.dk>
If ov is NULL, it will not be possible to take the lock in the first place,
so move the test up earlier.
The semantic match that finds the problem is as follows:
(http://coccinelle.lip6.fr/)
// <smpl>
@r exists@
expression E, E1;
identifier f;
statement S1,S3;
iterator iter;
@@
if ((E == NULL && ...) || ...)
{
... when != false ((E == NULL && ...) || ...)
when != true ((E != NULL && ...) || ...)
when != iter(E,...) S1
when != E = E1
(
sizeof(E->f)
|
* E->f
)
... when any
return ...;
}
else S3
// </smpl>
Signed-off-by: Julia Lawall <julia@diku.dk>
---
drivers/media/video/ov511.c | 8 +++-----
1 files changed, 3 insertions(+), 5 deletions(-)
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Comments
On Sun, 21 Mar 2010 22:31:06 +0100 (CET) Julia Lawall <julia@diku.dk> wrote:
> From: Julia Lawall <julia@diku.dk>
>
> If ov is NULL, it will not be possible to take the lock in the first place,
> so move the test up earlier.
>
> ...
>
> --- a/drivers/media/video/ov511.c
> +++ b/drivers/media/video/ov511.c
> @@ -5913,14 +5913,12 @@ ov51x_disconnect(struct usb_interface *intf)
>
> PDEBUG(3, "");
>
> + if (!ov)
> + return;
> +
> mutex_lock(&ov->lock);
> usb_set_intfdata (intf, NULL);
>
> - if (!ov) {
> - mutex_unlock(&ov->lock);
> - return;
> - }
> -
> /* Free device number */
> ov511_devused &= ~(1 << ov->nr);
I think we can pretty safely assume that we never get here with ov==NULL.
Oh well, I'll leave the test there for others to ponder.
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> I think we can pretty safely assume that we never get here with ov==NULL.
>
> Oh well, I'll leave the test there for others to ponder.
OK. I didn't read far enough in this email and sent another patch, in
case it's useful.
julia
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@@ -5913,14 +5913,12 @@ ov51x_disconnect(struct usb_interface *intf)
PDEBUG(3, "");
+ if (!ov)
+ return;
+
mutex_lock(&ov->lock);
usb_set_intfdata (intf, NULL);
- if (!ov) {
- mutex_unlock(&ov->lock);
- return;
- }
-
/* Free device number */
ov511_devused &= ~(1 << ov->nr);