[PATCH net-next v2] openvswitch: Pad OVS_PACKET_ATTR_PACKET if linear copy was performed

[Thomas Graf <tgraf@suug.ch>]

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@suug.ch>
---
v2: initialize padding to 0's

 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..3ca9121 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)
+		memset(skb_put(user_skb, plen), 0, plen);
+
 	((struct nlmsghdr *) user_skb->data)->nlmsg_len = user_skb->len;
 
 	err = genlmsg_unicast(ovs_dp_get_net(dp), user_skb, upcall_info->portid);