netfilter: ctnetlink: sleepable allocation with spin lock bh

This patch removes a GFP_KERNEL allocation while holding a spin lock with
bottom halves disabled in ctnetlink_change_helper().

This problem was introduced in 2.6.23 with the netfilter extension
infrastructure.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/nf_conntrack_netlink.c

@@ -968,7 +968,7 @@ ctnetlink_change_helper(struct nf_conn *ct, struct nlattr *cda[])
 		/* need to zero data of old helper */
 		memset(&help->help, 0, sizeof(help->help));
 	} else {
-		help = nf_ct_helper_ext_add(ct, GFP_KERNEL);
+		help = nf_ct_helper_ext_add(ct, GFP_ATOMIC);
 		if (help == NULL)
 			return -ENOMEM;
 	}