[PATCH] drivers/video/fbdev : dereference without an error test

[PATCH] drivers/video/fbdev : dereference without an error test

[Himangi Saraogi]

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:

// <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: Himangi Saraogi <himangi774@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
---
 drivers/video/fbdev/omap2/displays-new/panel-sony-acx565akm.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/video/fbdev/omap2/displays-new/panel-sony-acx565akm.c b/drivers/video/fbdev/omap2/displays-new/panel-sony-acx565akm.c
index c7ba4d8..acd9ff1 100644
--- a/drivers/video/fbdev/omap2/displays-new/panel-sony-acx565akm.c
+++ b/drivers/video/fbdev/omap2/displays-new/panel-sony-acx565akm.c
@@ -817,6 +817,10 @@ static int acx565akm_probe(struct spi_device *spi)
 
 	bldev = backlight_device_register("acx565akm", &ddata->spi->dev,
 			ddata, &acx565akm_bl_ops, &props);
+	if (IS_ERR(bldev)) {
+		r = PTR_ERR(bldev);
+		goto err_reg;
+	}
 	ddata->bl_dev = bldev;
 	if (ddata->has_cabc) {
 		r = sysfs_create_group(&bldev->dev.kobj, &bldev_attr_group);
@@ -862,6 +866,7 @@ err_reg:
 	sysfs_remove_group(&bldev->dev.kobj, &bldev_attr_group);
 err_sysfs:
 	backlight_device_unregister(bldev);
+err_reg:
 err_detect:
 err_gpio:
 	omap_dss_put_device(ddata->in);
-- 
1.9.1

Re: [PATCH] drivers/video/fbdev : dereference without an error test

[Tomi Valkeinen]

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On 21/06/14 18:57, Himangi Saraogi 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:
> 
> // <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: Himangi Saraogi <himangi774@gmail.com>
> Acked-by: Julia Lawall <julia.lawall@lip6.fr>
> ---
>  drivers/video/fbdev/omap2/displays-new/panel-sony-acx565akm.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/video/fbdev/omap2/displays-new/panel-sony-acx565akm.c b/drivers/video/fbdev/omap2/displays-new/panel-sony-acx565akm.c
> index c7ba4d8..acd9ff1 100644
> --- a/drivers/video/fbdev/omap2/displays-new/panel-sony-acx565akm.c
> +++ b/drivers/video/fbdev/omap2/displays-new/panel-sony-acx565akm.c
> @@ -817,6 +817,10 @@ static int acx565akm_probe(struct spi_device *spi)
>  
>  	bldev = backlight_device_register("acx565akm", &ddata->spi->dev,
>  			ddata, &acx565akm_bl_ops, &props);
> +	if (IS_ERR(bldev)) {
> +		r = PTR_ERR(bldev);
> +		goto err_reg;
> +	}
>  	ddata->bl_dev = bldev;
>  	if (ddata->has_cabc) {
>  		r = sysfs_create_group(&bldev->dev.kobj, &bldev_attr_group);
> @@ -862,6 +866,7 @@ err_reg:
>  	sysfs_remove_group(&bldev->dev.kobj, &bldev_attr_group);
>  err_sysfs:
>  	backlight_device_unregister(bldev);
> +err_reg:
>  err_detect:
>  err_gpio:
>  	omap_dss_put_device(ddata->in);

Thanks. This didn't compile, as there already was a "err_reg" label
defined. I fixed the issue, and queued for 3.17.

 Tomi



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