netdev - Re: [PATCHv1 net-next 0/5] netlink: mmap: kernel panic and some issues

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Date:	Mon, 17 Aug 2015 14:02:22 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	daniel@...earbox.net
Cc:	chamaken@...il.com, netdev@...r.kernel.org, fw@...len.de
Subject: Re: [PATCHv1 net-next 0/5] netlink: mmap: kernel panic and some
 issues

From: Daniel Borkmann <daniel@...earbox.net>
Date: Fri, 14 Aug 2015 12:38:21 +0200

> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index 67d2104..4307446 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -238,6 +238,13 @@ static void __netlink_deliver_tap(struct sk_buff
> *skb)
> 
>  static void netlink_deliver_tap(struct sk_buff *skb)
>  {
> +	/* Netlink mmaped skbs must not access shared info, and thus
> +	 * are not allowed to be cloned. For now, just don't allow
> +	 * them to get inspected by taps.
> +	 */
> +	if (netlink_skb_is_mmaped(skb))
> +		return;
> +

I would seriously rather see us do an expensive full copy of the SKB
than to have traffic which is unexpectedly invisible to taps.
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