linux-kernel - Re: [PATCH v2] drivers/video/via/ioctl.c: prevent reading uninitialized stack memory

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Date:	Thu, 16 Sep 2010 01:45:34 +0200
From:	Florian Tobias Schandinat <FlorianSchandinat@....de>
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 v2] drivers/video/via/ioctl.c: prevent reading uninitialized
 stack memory

Dan Rosenberg schrieb:
> Disregard previous version, which had a typo and wouldn't compile.
> Also, math is fun: the ioctl allows reading of 1968 BITS = 246 bytes,
> not 1968 bytes as previously reported.

Thanks, I will take care of getting it in mainline as soon as possible,

Florian Tobias Schandinat

> 
> The VIAFB_GET_INFO device ioctl allows unprivileged users to read 246
> 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_info));
> +
>  	viainfo.viafb_id = VIAID;
>  	viainfo.vendor_id = PCI_VIA_VENDOR_ID;
>  
> 
> 
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