From 32f5376003920a8bc1bd97c6cddcf42df0b6a833 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Mon, 18 Jun 2012 17:29:53 +0200 Subject: [PATCH] netfilter: nf_ct_helper: disable automatic helper re-assignment of different type 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 2918ec2e4509..c4bc637feb76 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); -- 2.30.2