Subject: Re: [PATCH 2/2] net: check for underlength tap writes

From: Max Krasnyanskiy <[email-masked]>
Date: Thu, 10 Apr 2008 11:19:38 -0700

Ack. I've been meaning to fix this as well.
Dave, can please merge it.

Thanx
Max

Rusty Russell wrote:
> If the user gives a packet under 14 bytes, we'll end up reading off the end
> of the skb (not oopsing, just reading off the end).
> 
> Signed-off-by: Rusty Russell <[email-masked]>
> 
> diff -r 99132ad16999 drivers/net/tun.c
> --- a/drivers/net/tun.c	Sat Apr 05 21:20:32 2008 +1100
> +++ b/drivers/net/tun.c	Sat Apr 05 22:47:20 2008 +1100
> @@ -286,8 +286,11 @@ static __inline__ ssize_t tun_get_user(s
>  			return -EFAULT;
>  	}
>  
> -	if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV)
> +	if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV) {
>  		align = NET_IP_ALIGN;
> +		if (unlikely(len < ETH_HLEN))
> +			return -EINVAL;
> +	}
>  
>  	if (!(skb = alloc_skb(len + align, GFP_KERNEL))) {
>  		tun->dev->stats.rx_dropped++;
>