kernel: fix conntrack leak for flow_offload connections

This was caused by a race condition between offload teardown and
conntrack gc bumping the timeout of offloaded connections

Signed-off-by: Felix Fietkau <nbd@nbd.name>

3 files changed, 123 insertions, 28 deletions

diff --git a/target/linux/generic/backport-4.14/370-netfilter-nf_flow_table-fix-offloaded-connection-tim.patch b/target/linux/generic/backport-4.14/370-netfilter-nf_flow_table-fix-offloaded-connection-tim.patch
new file mode 100644
index 0000000000..e68395c69e
--- /dev/null
+++ b/target/linux/generic/backport-4.14/370-netfilter-nf_flow_table-fix-offloaded-connection-tim.patch
@@ -0,0 +1,110 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Wed, 13 Jun 2018 12:33:39 +0200
+Subject: [PATCH] netfilter: nf_flow_table: fix offloaded connection timeout
+ corner case
+
+The full teardown of offloaded flows is deferred to a gc work item,
+however processing of packets by netfilter needs to happen immediately
+after a teardown is requested, because the conntrack state needs to be
+fixed up.
+
+Since the IPS_OFFLOAD_BIT is still kept until the teardown is complete,
+the netfilter conntrack gc can accidentally bump the timeout of a
+connection where offload was just stopped, causing a conntrack entry
+leak.
+
+Fix this by moving the conntrack timeout bumping from conntrack core to
+the nf_flow_offload and add a check to prevent bogus timeout bumps.
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/net/netfilter/nf_conntrack_core.c
++++ b/net/netfilter/nf_conntrack_core.c
+@@ -978,18 +978,6 @@ static bool gc_worker_can_early_drop(con
+ 	return false;
+ }
+ 
+-#define	DAY	(86400 * HZ)
+-
+-/* Set an arbitrary timeout large enough not to ever expire, this save
+- * us a check for the IPS_OFFLOAD_BIT from the packet path via
+- * nf_ct_is_expired().
+- */
+-static void nf_ct_offload_timeout(struct nf_conn *ct)
+-{
+-	if (nf_ct_expires(ct) < DAY / 2)
+-		ct->timeout = nfct_time_stamp + DAY;
+-}
+-
+ static void gc_worker(struct work_struct *work)
+ {
+ 	unsigned int min_interval = max(HZ / GC_MAX_BUCKETS_DIV, 1u);
+@@ -1026,10 +1014,8 @@ static void gc_worker(struct work_struct
+ 			tmp = nf_ct_tuplehash_to_ctrack(h);
+ 
+ 			scanned++;
+-			if (test_bit(IPS_OFFLOAD_BIT, &tmp->status)) {
+-				nf_ct_offload_timeout(tmp);
++			if (test_bit(IPS_OFFLOAD_BIT, &tmp->status))
+ 				continue;
+-			}
+ 
+ 			if (nf_ct_is_expired(tmp)) {
+ 				nf_ct_gc_expired(tmp);
+--- a/net/netfilter/nf_flow_table_core.c
++++ b/net/netfilter/nf_flow_table_core.c
+@@ -185,8 +185,27 @@ static const struct rhashtable_params nf
+ 	.automatic_shrinking	= true,
+ };
+ 
++#define	DAY	(86400 * HZ)
++
++/* Set an arbitrary timeout large enough not to ever expire, this save
++ * us a check for the IPS_OFFLOAD_BIT from the packet path via
++ * nf_ct_is_expired().
++ */
++static void nf_ct_offload_timeout(struct flow_offload *flow)
++{
++	struct flow_offload_entry *entry;
++	struct nf_conn *ct;
++
++	entry = container_of(flow, struct flow_offload_entry, flow);
++	ct = entry->ct;
++
++	if (nf_ct_expires(ct) < DAY / 2)
++		ct->timeout = nfct_time_stamp + DAY;
++}
++
+ int flow_offload_add(struct nf_flowtable *flow_table, struct flow_offload *flow)
+ {
++	nf_ct_offload_timeout(flow);
+ 	flow->timeout = (u32)jiffies;
+ 
+ 	rhashtable_insert_fast(&flow_table->rhashtable,
+@@ -307,6 +326,8 @@ static int nf_flow_offload_gc_step(struc
+ 	rhashtable_walk_start(&hti);
+ 
+ 	while ((tuplehash = rhashtable_walk_next(&hti))) {
++		bool teardown;
++
+ 		if (IS_ERR(tuplehash)) {
+ 			err = PTR_ERR(tuplehash);
+ 			if (err != -EAGAIN)
+@@ -319,9 +340,13 @@ static int nf_flow_offload_gc_step(struc
+ 
+ 		flow = container_of(tuplehash, struct flow_offload, tuplehash[0]);
+ 
+-		if (nf_flow_has_expired(flow) ||
+-		    (flow->flags & (FLOW_OFFLOAD_DYING |
+-				    FLOW_OFFLOAD_TEARDOWN)))
++		teardown = flow->flags & (FLOW_OFFLOAD_DYING |
++					  FLOW_OFFLOAD_TEARDOWN);
++
++		if (!teardown)
++			nf_ct_offload_timeout(flow);
++
++		if (nf_flow_has_expired(flow) || teardown)
+ 			flow_offload_del(flow_table, flow);
+ 	}
+ out:
diff --git a/target/linux/generic/pending-4.14/640-netfilter-nf_flow_table-add-hardware-offload-support.patch b/target/linux/generic/pending-4.14/640-netfilter-nf_flow_table-add-hardware-offload-support.patch
index df48db04eb..ad77215843 100644
--- a/target/linux/generic/pending-4.14/640-netfilter-nf_flow_table-add-hardware-offload-support.patch
+++ b/target/linux/generic/pending-4.14/640-netfilter-nf_flow_table-add-hardware-offload-support.patch
@@ -156,7 +156,7 @@ Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
  obj-$(CONFIG_NETFILTER_XTABLES) += x_tables.o xt_tcpudp.o
 --- a/net/netfilter/nf_flow_table_core.c
 +++ b/net/netfilter/nf_flow_table_core.c
-@@ -199,10 +199,16 @@ int flow_offload_add(struct nf_flowtable
+@@ -218,10 +218,16 @@ int flow_offload_add(struct nf_flowtable
  }
  EXPORT_SYMBOL_GPL(flow_offload_add);
  
@@ -173,7 +173,7 @@ Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
  
  	rhashtable_remove_fast(&flow_table->rhashtable,
  			       &flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].node,
-@@ -214,6 +220,9 @@ static void flow_offload_del(struct nf_f
+@@ -233,6 +239,9 @@ static void flow_offload_del(struct nf_f
  	e = container_of(flow, struct flow_offload_entry, flow);
  	clear_bit(IPS_OFFLOAD_BIT, &e->ct->status);
  
@@ -183,32 +183,17 @@ Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
  	flow_offload_free(flow);
  }
  
-@@ -307,6 +316,7 @@ static int nf_flow_offload_gc_step(struc
- 	rhashtable_walk_start(&hti);
+@@ -346,6 +355,9 @@ static int nf_flow_offload_gc_step(struc
+ 		if (!teardown)
+ 			nf_ct_offload_timeout(flow);
  
- 	while ((tuplehash = rhashtable_walk_next(&hti))) {
-+		bool teardown;
- 		if (IS_ERR(tuplehash)) {
- 			err = PTR_ERR(tuplehash);
- 			if (err != -EAGAIN)
-@@ -319,9 +329,13 @@ static int nf_flow_offload_gc_step(struc
- 
- 		flow = container_of(tuplehash, struct flow_offload, tuplehash[0]);
- 
--		if (nf_flow_has_expired(flow) ||
--		    (flow->flags & (FLOW_OFFLOAD_DYING |
--				    FLOW_OFFLOAD_TEARDOWN)))
-+		teardown = flow->flags & (FLOW_OFFLOAD_DYING |
-+					  FLOW_OFFLOAD_TEARDOWN);
-+
 +		if (nf_flow_in_hw(flow) && !teardown)
 +			continue;
 +
-+		if (nf_flow_has_expired(flow) || teardown)
+ 		if (nf_flow_has_expired(flow) || teardown)
  			flow_offload_del(flow_table, flow);
  	}
- out:
-@@ -456,10 +470,43 @@ int nf_flow_dnat_port(const struct flow_
+@@ -481,10 +493,43 @@ int nf_flow_dnat_port(const struct flow_
  }
  EXPORT_SYMBOL_GPL(nf_flow_dnat_port);
  
@@ -252,7 +237,7 @@ Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
  	INIT_DEFERRABLE_WORK(&flowtable->gc_work, nf_flow_offload_work_gc);
  
  	err = rhashtable_init(&flowtable->rhashtable,
-@@ -497,6 +544,8 @@ static void nf_flow_table_iterate_cleanu
+@@ -522,6 +567,8 @@ static void nf_flow_table_iterate_cleanu
  {
  	nf_flow_table_iterate(flowtable, nf_flow_table_do_cleanup, dev);
  	flush_delayed_work(&flowtable->gc_work);
@@ -261,7 +246,7 @@ Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
  }
  
  void nf_flow_table_cleanup(struct net *net, struct net_device *dev)
-@@ -510,6 +559,26 @@ void nf_flow_table_cleanup(struct net *n
+@@ -535,6 +582,26 @@ void nf_flow_table_cleanup(struct net *n
  }
  EXPORT_SYMBOL_GPL(nf_flow_table_cleanup);
  
@@ -288,7 +273,7 @@ Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
  void nf_flow_table_free(struct nf_flowtable *flow_table)
  {
  	mutex_lock(&flowtable_lock);
-@@ -519,9 +588,58 @@ void nf_flow_table_free(struct nf_flowta
+@@ -544,9 +611,58 @@ void nf_flow_table_free(struct nf_flowta
  	nf_flow_table_iterate(flow_table, nf_flow_table_do_cleanup, NULL);
  	WARN_ON(!nf_flow_offload_gc_step(flow_table));
  	rhashtable_destroy(&flow_table->rhashtable);
diff --git a/target/linux/generic/pending-4.14/645-netfilter-nf_flow_table-rework-hardware-offload-time.patch b/target/linux/generic/pending-4.14/645-netfilter-nf_flow_table-rework-hardware-offload-time.patch
index 8da15bc336..2b3725f81e 100644
--- a/target/linux/generic/pending-4.14/645-netfilter-nf_flow_table-rework-hardware-offload-time.patch
+++ b/target/linux/generic/pending-4.14/645-netfilter-nf_flow_table-rework-hardware-offload-time.patch
@@ -26,9 +26,9 @@ Signed-off-by: Felix Fietkau <nbd@nbd.name>
  	struct flow_offload_tuple_rhash		tuplehash[FLOW_OFFLOAD_DIR_MAX];
 --- a/net/netfilter/nf_flow_table_core.c
 +++ b/net/netfilter/nf_flow_table_core.c
-@@ -332,7 +332,7 @@ static int nf_flow_offload_gc_step(struc
- 		teardown = flow->flags & (FLOW_OFFLOAD_DYING |
- 					  FLOW_OFFLOAD_TEARDOWN);
+@@ -355,7 +355,7 @@ static int nf_flow_offload_gc_step(struc
+ 		if (!teardown)
+ 			nf_ct_offload_timeout(flow);
  
 -		if (nf_flow_in_hw(flow) && !teardown)
 +		if ((flow->flags & FLOW_OFFLOAD_KEEP) && !teardown)