netdev - Re: [PATCH net] net: test nouarg before dereferencing zerocopy pointers

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Message-Id: <20190516.121841.1544241385308476523.davem@davemloft.net>
Date:   Thu, 16 May 2019 12:18:41 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     willemdebruijn.kernel@...il.com
Cc:     netdev@...r.kernel.org, edumazet@...gle.com, willemb@...gle.com
Subject: Re: [PATCH net] net: test nouarg before dereferencing zerocopy
 pointers

From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Date: Wed, 15 May 2019 13:29:16 -0400

> From: Willem de Bruijn <willemb@...gle.com>
> 
> Zerocopy skbs without completion notification were added for packet
> sockets with PACKET_TX_RING user buffers. Those signal completion
> through the TP_STATUS_USER bit in the ring. Zerocopy annotation was
> added only to avoid premature notification after clone or orphan, by
> triggering a copy on these paths for these packets.
> 
> The mechanism had to define a special "no-uarg" mode because packet
> sockets already use skb_uarg(skb) == skb_shinfo(skb)->destructor_arg
> for a different pointer.
> 
> Before deferencing skb_uarg(skb), verify that it is a real pointer.
> 
> Fixes: 5cd8d46ea1562 ("packet: copy user buffers before orphan or clone")
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>

Applied and queued up for -stable, thanks.