netdev - Re: [PATCH net-next] openvswitch: Pad OVS_PACKET_ATTR

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Date:	Tue, 14 Jan 2014 16:19:11 +0000
From:	Thomas Graf <tgraf@...g.ch>
To:	Zoltan Kiss <zoltan.kiss@...rix.com>
Cc:	Thomas Graf <tgraf@...hat.com>, Jesse Gross <jesse@...ira.com>,
	David Miller <davem@...emloft.net>,
	"dev@...nvswitch.org" <dev@...nvswitch.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] openvswitch: Pad OVS_PACKET_ATTR_PACKET if
 linear copy was performed

On 01/14/14 at 04:16pm, Thomas Graf wrote:
> While the zerocopy method is correctly omitted if user space
> does not support unaligned Netlink messages. The attribute is
> still not padded correctly as skb_zerocopy() will not ensure
> padding and the attribute size is no longer pre calculated
> though nla_reserve() which ensured padding previously.
> 
> This patch applies appropriate padding if a linear data copy
> was performed in skb_zerocopy().
> 
> Signed-off-by: Thomas Graf <tgraf@...g.ch>
> ---
>  net/openvswitch/datapath.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
> index df46928..24e93f5 100644
> --- a/net/openvswitch/datapath.c
> +++ b/net/openvswitch/datapath.c
> @@ -396,7 +396,7 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
>  		.dst_sk = ovs_dp_get_net(dp)->genl_sock,
>  		.snd_portid = upcall_info->portid,
>  	};
> -	size_t len;
> +	size_t len, plen;
>  	unsigned int hlen;
>  	int err, dp_ifindex;
>  
> @@ -466,6 +466,11 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
>  
>  	skb_zerocopy(user_skb, skb, skb->len, hlen);
>  
> +	/* Pad OVS_PACKET_ATTR_PACKET if linear copy was performed */
> +	if (!(dp->user_features & OVS_DP_F_UNALIGNED) &&
> +	    (plen = (ALIGN(user_skb->len, NLA_ALIGNTO) - user_skb->len)) > 0)
> +		skb_put(user_skb, plen);

While this fixes the padding issue, it leaves the padding
uninitialized, I will send v2 with an additional memset().
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