linux-kernel - Re: [PATCH] drivers/net/tulip/de4x5.c: prevent reading uninitialized stack memory

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Message-ID: <4C90E970.6020700@suse.com>
Date:	Wed, 15 Sep 2010 11:42:40 -0400
From:	Jeff Mahoney <jeffm@...e.com>
To:	Dan Rosenberg <dan.j.rosenberg@...il.com>
Cc:	grundler@...isc-linux.org, kyle@...artin.ca,
	linux-kernel@...r.kernel.org, security@...nel.org
Subject: Re: [PATCH] drivers/net/tulip/de4x5.c: prevent reading uninitialized
 stack memory

On 09/11/2010 07:46 PM, Dan Rosenberg wrote:
> The DE4X5_GET_REG device ioctl allows unprivileged users to read 32
> bytes of uninitialized stack memory, because it copies the
> uninitialized "addr" member instead of the intended "lval" member.
> This patch takes care of it.
>
> Signed-off-by: Dan Rosenberg<dan.j.rosenberg@...il.com>

No. This patch may be considered for correctness, but there's no 
security issue here.

'tmp' is a union, not a struct. Writes to lval are the same as writes to 
addr. The length is correctly determined so that only initialized memory 
is used.

-Jeff

> --- linux-2.6.35.4.orig/drivers/net/tulip/de4x5.c	2010-09-11
> 19:12:27.000000000 -0400
> +++ linux-2.6.35.4/drivers/net/tulip/de4x5.c	2010-09-11 19:17:12.000000000 -0400
> @@ -5474,7 +5474,7 @@ de4x5_ioctl(struct net_device *dev, stru
>   	tmp.lval[6] = inl(DE4X5_STRR); j+=4;
>   	tmp.lval[7] = inl(DE4X5_SIGR); j+=4;
>   	ioc->len = j;
> -	if (copy_to_user(ioc->data, tmp.addr, ioc->len)) return -EFAULT;
> +	if (copy_to_user(ioc->data, tmp.lval, ioc->len)) return -EFAULT;
>   	break;
>
>   #define DE4X5_DUMP              0x0f /* Dump the DE4X5 Status */
> --
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-- 
Jeff Mahoney
SUSE Labs
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