linux-kernel - Re: [PATCH] drivers/video/via/ioctl.c: prevent reading uninitialized stack memory

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Date:	Thu, 16 Sep 2010 12:07:45 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Dan Rosenberg <drosenberg@...curity.com>
Cc:	JosephChan@....com.tw, ScottFang@...tech.com.cn,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	security@...nel.org, stable@...nel.org
Subject: Re: [PATCH] drivers/video/via/ioctl.c: prevent reading
 uninitialized stack memory

On Wed, Sep 15, 2010 at 05:44:19PM -0400, Dan Rosenberg wrote:
> The VIAFB_GET_INFO device ioctl allows unprivileged users to read 1968
> bytes of uninitialized stack memory, because the "reserved" member of
> the viafb_ioctl_info struct declared on the stack is not altered or
> zeroed before being copied back to the user.  This patch takes care of
> it.
> 
> Signed-off-by: Dan Rosenberg <dan.j.rosenberg@...il.com>
> 
> --- linux-2.6.35.4.orig/drivers/video/via/ioctl.c	2010-08-26 19:47:12.000000000 -0400
> +++ linux-2.6.35.4/drivers/video/via/ioctl.c	2010-09-15 11:53:29.997375748 -0400
> @@ -25,6 +25,8 @@ int viafb_ioctl_get_viafb_info(u_long ar
>  {
>  	struct viafb_ioctl_info viainfo;
>  
> +	memset(&viainfo, 0, sizeof(struct viafb_ioctl));
> +

Again, this could probably be better off as:

-  	struct viafb_ioctl_info viainfo;
+  	struct viafb_ioctl_info viainfo = {
+  		.viafb_id = VIAID,
+ 		.vendor_id = PCI_VIA_VENDOR_ID,
+	};

-  	viainfo.viafb_id = VIAID;
-  	viainfo.vendor_id = PCI_VIA_VENDOR_ID;

-- Steve

>  	viainfo.viafb_id = VIAID;
>  	viainfo.vendor_id = PCI_VIA_VENDOR_ID;
>  
> 
> 
> 
> --
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