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SubjectRe: [PATCH] drivers/acpi: dereference without an error test
applied.

thanks,
-len

On Fri, 26 Sep 2008, Julien Brunel wrote:

> After a variable is assigned the result of backlight_device_register, an error
> test should be performed before a dereference.
>
> A simplified version of the semantic match that finds this problem is
> as follows:
> (http://www.emn.fr/x-info/coccinelle/)
> // <smpl>
> @def0@
> expression x;
> position p0;
> @@
>
> x@p0 = backlight_device_register(...)
>
> @protected@
> expression def0.x,E;
> position def0.p0;
> position p;
> statement S;
> @@
> x@p0
> ... when != x = E
> if (!IS_ERR(x) && ...) {<... x@p ...>} else S
>
> @unprotected@
> expression def0.x,E;
> identifier fld;
> position def0.p0;
> position p != protected.p;
> @@
> x@p0
> ... when != x = E
> * x@p->fld
> // </smpl>
>
> Signed-off-by: Julien Brunel <brunel@diku.dk>
> Signed-off-by: Julia Lawall <julia@diku.dk>
>
> ---
> drivers/acpi/video.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff -u -p a/drivers/acpi/video.c b/drivers/acpi/video.c
> --- a/drivers/acpi/video.c
> +++ b/drivers/acpi/video.c
> @@ -752,6 +752,8 @@ static void acpi_video_device_find_cap(s
> sprintf(name, "acpi_video%d", count++);
> device->backlight = backlight_device_register(name,
> NULL, device, &acpi_backlight_ops);
> + if (IS_ERR(device->backlight))
> + return;
> device->backlight->props.max_brightness = device->brightness->count-3;
> /*
> * If there exists the _BQC object, the _BQC object will be
> --
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>


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