Re: [patch] Fix snd-usb-audio in 32-bit compat environemt

[Alexey Dobriyan]

On Sat, Feb 18, 2006 at 07:50:37PM +0100, Juergen Kreileder wrote:
> I'm getting oopses with snd-usb-audio in 32-bit compat environments:
> control_compat.c:get_ctl_type() doesn't initialize 'info', so
> 'itemlist[uinfo->value.enumerated.item]' in
> usbmixer.c:mixer_ctl_selector_info() might access random memory
> (The 'if ((int)uinfo->value.enumerated.item >= cval->max)' doesn't fix
> all problems because of the unsigned -> signed conversion.)

IMO, what you did is an overkill. Does this patch fixes your problem?

Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>

--- a/sound/core/control_compat.c
+++ b/sound/core/control_compat.c
@@ -176,6 +176,7 @@ static int get_ctl_type(struct snd_card
 		up_read(&card->controls_rwsem);
 		return -ENXIO;
 	}
+	memset(info, 0, sizeof(struct snd_ctl_elem_info));
 	info.id = *id;
 	err = kctl->info(kctl, &info);
 	up_read(&card->controls_rwsem);

> --- linux-mm-vanilla/sound/core/control_compat.c
> +++ linux-mm/sound/core/control_compat.c
> @@ -167,7 +167,7 @@ static int get_ctl_type(struct snd_card
>  			int *countp)
>  {
>  	struct snd_kcontrol *kctl;
> -	struct snd_ctl_elem_info info;
> +	struct snd_ctl_elem_info *info;
>  	int err;
>
>  	down_read(&card->controls_rwsem);
> @@ -176,13 +176,19 @@ static int get_ctl_type(struct snd_card
>  		up_read(&card->controls_rwsem);
>  		return -ENXIO;
>  	}
> -	info.id = *id;
> -	err = kctl->info(kctl, &info);
> +	info = kzalloc(sizeof(*info), GFP_KERNEL);
> +	if (info == NULL) {
> +		up_read(&card->controls_rwsem);
> +		return -ENOMEM;
> +	}
> +	info->id = *id;
> +	err = kctl->info(kctl, info);
>  	up_read(&card->controls_rwsem);
>  	if (err >= 0) {
> -		err = info.type;
> -		*countp = info.count;
> +		err = info->type;
> +		*countp = info->count;
>  	}
> +	kfree(info);
>  	return err;
>  }

-
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