[ 100/136 ] netfilter: nf_ct_helper: dont discard helper if it is actually thesame

[Steven Rostedt]

3.6.11.4 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Florian Westphal <fw@xxxxxxxxx>

[ Upstream commit 6e2f0aa8cf8892868bf2c19349cb5d7c407f690d ]

commit (32f5376 netfilter: nf_ct_helper: disable automatic helper
re-assignment of different type) broke transparent proxy scenarios.

For example, initial helper lookup might yield "ftp" (dport 21),
while re-lookup after REDIRECT yields "ftp-2121".

This causes the autoassign code to toss the ftp helper, even
though these are just different instances of the same helper.

Change the test to check for the helper function address instead
of the helper address, as suggested by Pablo.

Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 net/netfilter/nf_conntrack_helper.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
index c4bc637..622dd4d 100644
--- a/net/netfilter/nf_conntrack_helper.c
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -232,7 +232,9 @@ int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
 		/* We only allow helper re-assignment of the same sort since
 		 * we cannot reallocate the helper extension area.
 		 */
-		if (help->helper != helper) {
+		struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
+
+		if (tmp && tmp->help != helper->help) {
 			RCU_INIT_POINTER(help->helper, NULL);
 			goto out;
 		}
-- 
1.7.10.4


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