Commit 32f53760 authored Jun 18, 2012 by Pablo Neira Ayuso

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 <pablo@netfilter.org>

parent fd7462de

net/netfilter/nf_conntrack_helper.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -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);