From patchwork Tue Jun 19 03:16:27 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [2/4] netfilter: nf_ct_helper: disable automatic helper re-assignment of different type Date: Mon, 18 Jun 2012 17:16:27 -0000 From: Pablo Neira X-Patchwork-Id: 165635 Message-Id: <1340075789-6196-3-git-send-email-pablo@netfilter.org> To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org From: Pablo Neira Ayuso This patch modifies __nf_ct_try_assign_helper in a way that invalidates support for the following scenario: 1) attach the helper A for first time when the conntrack is created 2) attach new (different) helper B due to changes the reply tuple caused by NAT eg. port redirection from TCP/21 to TCP/5060 with both FTP and SIP helpers loaded, which seems to be a quite unorthodox scenario. I can provide a more elaborated patch to support this scenario but explicit helper attachment provides a better solution for this since now the use can attach the helpers consistently, without relying on the automatic helper lookup magic. This patch fixes a possible out of bound zeroing of the conntrack helper extension if the helper B uses more memory for its private data than helper A. Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nf_conntrack_helper.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c index 2918ec2..c4bc637 100644 --- a/net/netfilter/nf_conntrack_helper.c +++ b/net/netfilter/nf_conntrack_helper.c @@ -229,7 +229,13 @@ int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl, goto out; } } else { - memset(help->data, 0, helper->data_len); + /* We only allow helper re-assignment of the same sort since + * we cannot reallocate the helper extension area. + */ + if (help->helper != helper) { + RCU_INIT_POINTER(help->helper, NULL); + goto out; + } } rcu_assign_pointer(help->helper, helper);