openvswitch: Fix kernel panic on ovs_flow_free

Both mega flow mask's reference counter and per flow table mask list
should only be accessed when holding ovs_mutex() lock. However
this is not true with ovs_flow_table_flush(). The patch fixes this bug.

Reported-by: Joe Stringer <joestringer@nicira.com>
Signed-off-by: Andy Zhou <azhou@nicira.com>
Signed-off-by: Jesse Gross <jesse@nicira.com>

3 files changed, 47 insertions, 48 deletions

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index d1a73a6102f8..e1b337e0bf4d 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -55,6 +55,7 @@
 
 #include "datapath.h"
 #include "flow.h"
+#include "flow_table.h"
 #include "flow_netlink.h"
 #include "vport-internal_dev.h"
 #include "vport-netdev.h"
@@ -160,7 +161,6 @@ static void destroy_dp_rcu(struct rcu_head *rcu)
 {
         struct datapath *dp = container_of(rcu, struct datapath, rcu);
 
-        ovs_flow_tbl_destroy(&dp->table);
         free_percpu(dp->stats_percpu);
         release_net(ovs_dp_get_net(dp));
         kfree(dp->ports);
@@ -1287,7 +1287,7 @@ err_destroy_ports_array:
 err_destroy_percpu:
         free_percpu(dp->stats_percpu);
 err_destroy_table:
-        ovs_flow_tbl_destroy(&dp->table);
+        ovs_flow_tbl_destroy(&dp->table, false);
 err_free_dp:
         release_net(ovs_dp_get_net(dp));
         kfree(dp);
@@ -1314,10 +1314,13 @@ static void __dp_destroy(struct datapath *dp)
         list_del_rcu(&dp->list_node);
 
         /* OVSP_LOCAL is datapath internal port. We need to make sure that
-         * all port in datapath are destroyed first before freeing datapath.
+         * all ports in datapath are destroyed first before freeing datapath.
          */
         ovs_dp_detach_port(ovs_vport_ovsl(dp, OVSP_LOCAL));
 
+        /* RCU destroy the flow table */
+        ovs_flow_tbl_destroy(&dp->table, true);
+
         call_rcu(&dp->rcu, destroy_dp_rcu);
 }
 
diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c
index c58a0fe3c889..bd14052ed342 100644
--- a/net/openvswitch/flow_table.c
+++ b/net/openvswitch/flow_table.c
@@ -153,29 +153,27 @@ static void rcu_free_flow_callback(struct rcu_head *rcu)
         flow_free(flow);
 }
 
-static void flow_mask_del_ref(struct sw_flow_mask *mask, bool deferred)
+void ovs_flow_free(struct sw_flow *flow, bool deferred)
 {
-        if (!mask)
+        if (!flow)
                 return;
 
-        BUG_ON(!mask->ref_count);
-        mask->ref_count--;
+        ASSERT_OVSL();
 
-        if (!mask->ref_count) {
-                list_del_rcu(&mask->list);
-                if (deferred)
-                        kfree_rcu(mask, rcu);
-                else
-                        kfree(mask);
-        }
-}
+        if (flow->mask) {
+                struct sw_flow_mask *mask = flow->mask;
 
-void ovs_flow_free(struct sw_flow *flow, bool deferred)
-{
-        if (!flow)
-                return;
+                BUG_ON(!mask->ref_count);
+                mask->ref_count--;
 
-        flow_mask_del_ref(flow->mask, deferred);
+                if (!mask->ref_count) {
+                        list_del_rcu(&mask->list);
+                        if (deferred)
+                                kfree_rcu(mask, rcu);
+                        else
+                                kfree(mask);
+                }
+        }
 
         if (deferred)
                 call_rcu(&flow->rcu, rcu_free_flow_callback);
@@ -188,26 +186,9 @@ static void free_buckets(struct flex_array *buckets)
         flex_array_free(buckets);
 }
 
+
 static void __table_instance_destroy(struct table_instance *ti)
 {
-        int i;
-
-        if (ti->keep_flows)
-                goto skip_flows;
-
-        for (i = 0; i < ti->n_buckets; i++) {
-                struct sw_flow *flow;
-                struct hlist_head *head = flex_array_get(ti->buckets, i);
-                struct hlist_node *n;
-                int ver = ti->node_ver;
-
-                hlist_for_each_entry_safe(flow, n, head, hash_node[ver]) {
-                        hlist_del(&flow->hash_node[ver]);
-                        ovs_flow_free(flow, false);
-                }
-        }
-
-skip_flows:
         free_buckets(ti->buckets);
         kfree(ti);
 }
@@ -258,20 +239,38 @@ static void flow_tbl_destroy_rcu_cb(struct rcu_head *rcu)
 
 static void table_instance_destroy(struct table_instance *ti, bool deferred)
 {
+        int i;
+
         if (!ti)
                 return;
 
+        if (ti->keep_flows)
+                goto skip_flows;
+
+        for (i = 0; i < ti->n_buckets; i++) {
+                struct sw_flow *flow;
+                struct hlist_head *head = flex_array_get(ti->buckets, i);
+                struct hlist_node *n;
+                int ver = ti->node_ver;
+
+                hlist_for_each_entry_safe(flow, n, head, hash_node[ver]) {
+                        hlist_del_rcu(&flow->hash_node[ver]);
+                        ovs_flow_free(flow, deferred);
+                }
+        }
+
+skip_flows:
         if (deferred)
                 call_rcu(&ti->rcu, flow_tbl_destroy_rcu_cb);
         else
                 __table_instance_destroy(ti);
 }
 
-void ovs_flow_tbl_destroy(struct flow_table *table)
+void ovs_flow_tbl_destroy(struct flow_table *table, bool deferred)
 {
         struct table_instance *ti = ovsl_dereference(table->ti);
 
-        table_instance_destroy(ti, false);
+        table_instance_destroy(ti, deferred);
 }
 
 struct sw_flow *ovs_flow_tbl_dump_next(struct table_instance *ti,
@@ -504,16 +503,11 @@ static struct sw_flow_mask *mask_alloc(void)
 
         mask = kmalloc(sizeof(*mask), GFP_KERNEL);
         if (mask)
-                mask->ref_count = 0;
+                mask->ref_count = 1;
 
         return mask;
 }
 
-static void mask_add_ref(struct sw_flow_mask *mask)
-{
-        mask->ref_count++;
-}
-
 static bool mask_equal(const struct sw_flow_mask *a,
                        const struct sw_flow_mask *b)
 {
@@ -554,9 +548,11 @@ static int flow_mask_insert(struct flow_table *tbl, struct sw_flow *flow,
                 mask->key = new->key;
                 mask->range = new->range;
                 list_add_rcu(&mask->list, &tbl->mask_list);
+        } else {
+                BUG_ON(!mask->ref_count);
+                mask->ref_count++;
         }
 
-        mask_add_ref(mask);
         flow->mask = mask;
         return 0;
 }
diff --git a/net/openvswitch/flow_table.h b/net/openvswitch/flow_table.h
index 1996e34c0fd8..baaeb101924d 100644
--- a/net/openvswitch/flow_table.h
+++ b/net/openvswitch/flow_table.h
@@ -60,7 +60,7 @@ void ovs_flow_free(struct sw_flow *, bool deferred);
 
 int ovs_flow_tbl_init(struct flow_table *);
 int ovs_flow_tbl_count(struct flow_table *table);
-void ovs_flow_tbl_destroy(struct flow_table *table);
+void ovs_flow_tbl_destroy(struct flow_table *table, bool deferred);
 int ovs_flow_tbl_flush(struct flow_table *flow_table);
 
 int ovs_flow_tbl_insert(struct flow_table *table, struct sw_flow *flow,