netdev - Re: [patch v3] fix stack overflow in pktgen_if

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Date:	Fri, 29 Oct 2010 01:11:57 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Dan Carpenter <error27@...il.com>
Cc:	Nelson Elhage <nelhage@...lice.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Robert Olsson <robert.olsson@....uu.se>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	netdev@...r.kernel.org
Subject: Re: [patch v3] fix stack overflow in pktgen_if_write()

Dan Carpenter <error27@...il.com> writes:

> Reported-by: Nelson Elhage <nelhage@...lice.com>
> Signed-off-by: Dan Carpenter <error27@...il.com>
> ---
> v3:  just use kmalloc()
>
> diff --git a/net/core/pktgen.c b/net/core/pktgen.c
> index 2c0df0f..c8d3620 100644
> --- a/net/core/pktgen.c
> +++ b/net/core/pktgen.c
> @@ -887,12 +887,17 @@ static ssize_t pktgen_if_write(struct file *file,
>  	i += len;
>  
>  	if (debug) {
> -		char tb[count + 1];
> +		char *tb;
> +
> +		tb = kmalloc(count + 1, GFP_KERNEL);


This is still trivially exploitable (for root) -- think what happens
when count is near ULONG_MAX

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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