[NETFILTER]: ip_nat: properly use RCU API for ip_nat_protos array

Replace preempt_{enable,disable} based RCU by proper use of the
RCU API and add missing rcu_read_lock/rcu_read_unlock calls in
paths used outside of packet processing context (nfnetlink_conntrack).

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 29 insertions, 32 deletions

diff --git a/net/ipv4/netfilter/ip_nat_core.c b/net/ipv4/netfilter/ip_nat_core.c
index 275a4d3faf0a..85ae0cabc8b5 100644
--- a/net/ipv4/netfilter/ip_nat_core.c
+++ b/net/ipv4/netfilter/ip_nat_core.c
@@ -50,7 +50,7 @@ static struct ip_nat_protocol *ip_nat_protos[MAX_IP_NAT_PROTO];
 static inline struct ip_nat_protocol *
 __ip_nat_proto_find(u_int8_t protonum)
 {
-        return ip_nat_protos[protonum];
+        return rcu_dereference(ip_nat_protos[protonum]);
 }
 
 struct ip_nat_protocol *
@@ -58,13 +58,11 @@ ip_nat_proto_find_get(u_int8_t protonum)
 {
         struct ip_nat_protocol *p;
 
-        /* we need to disable preemption to make sure 'p' doesn't get
-         * removed until we've grabbed the reference */
-        preempt_disable();
+        rcu_read_lock();
         p = __ip_nat_proto_find(protonum);
         if (!try_module_get(p->me))
                 p = &ip_nat_unknown_protocol;
-        preempt_enable();
+        rcu_read_unlock();
 
         return p;
 }
@@ -120,8 +118,8 @@ static int
 in_range(const struct ip_conntrack_tuple *tuple,
          const struct ip_nat_range *range)
 {
-        struct ip_nat_protocol *proto =
-                                __ip_nat_proto_find(tuple->dst.protonum);
+        struct ip_nat_protocol *proto;
+        int ret = 0;
 
         /* If we are supposed to map IPs, then we must be in the
            range specified, otherwise let this drag us onto a new src IP. */
@@ -131,12 +129,15 @@ in_range(const struct ip_conntrack_tuple *tuple,
                         return 0;
         }
 
+        rcu_read_lock();
+        proto = __ip_nat_proto_find(tuple->dst.protonum);
         if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)
             || proto->in_range(tuple, IP_NAT_MANIP_SRC,
                                &range->min, &range->max))
-                return 1;
+                ret = 1;
+        rcu_read_unlock();
 
-        return 0;
+        return ret;
 }
 
 static inline int
@@ -260,27 +261,25 @@ get_unique_tuple(struct ip_conntrack_tuple *tuple,
         /* 3) The per-protocol part of the manip is made to map into
            the range to make a unique tuple. */
 
-        proto = ip_nat_proto_find_get(orig_tuple->dst.protonum);
+        rcu_read_lock();
+        proto = __ip_nat_proto_find(orig_tuple->dst.protonum);
 
         /* Change protocol info to have some randomization */
         if (range->flags & IP_NAT_RANGE_PROTO_RANDOM) {
                 proto->unique_tuple(tuple, range, maniptype, conntrack);
-                ip_nat_proto_put(proto);
-                return;
+                goto out;
         }
 
         /* Only bother mapping if it's not already in range and unique */
         if ((!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)
              || proto->in_range(tuple, maniptype, &range->min, &range->max))
-            && !ip_nat_used_tuple(tuple, conntrack)) {
-                ip_nat_proto_put(proto);
-                return;
-        }
+            && !ip_nat_used_tuple(tuple, conntrack))
+                goto out;
 
         /* Last change: get protocol to try to obtain unique tuple. */
         proto->unique_tuple(tuple, range, maniptype, conntrack);
-
-        ip_nat_proto_put(proto);
+out:
+        rcu_read_unlock();
 }
 
 unsigned int
@@ -360,12 +359,11 @@ manip_pkt(u_int16_t proto,
         iph = (void *)(*pskb)->data + iphdroff;
 
         /* Manipulate protcol part. */
-        p = ip_nat_proto_find_get(proto);
-        if (!p->manip_pkt(pskb, iphdroff, target, maniptype)) {
-                ip_nat_proto_put(p);
+
+        /* rcu_read_lock()ed by nf_hook_slow */
+        p = __ip_nat_proto_find(proto);
+        if (!p->manip_pkt(pskb, iphdroff, target, maniptype))
                 return 0;
-        }
-        ip_nat_proto_put(p);
 
         iph = (void *)(*pskb)->data + iphdroff;
 
@@ -515,7 +513,7 @@ int ip_nat_protocol_register(struct ip_nat_protocol *proto)
                 ret = -EBUSY;
                 goto out;
         }
-        ip_nat_protos[proto->protonum] = proto;
+        rcu_assign_pointer(ip_nat_protos[proto->protonum], proto);
  out:
         write_unlock_bh(&ip_nat_lock);
         return ret;
@@ -526,11 +524,10 @@ EXPORT_SYMBOL(ip_nat_protocol_register);
 void ip_nat_protocol_unregister(struct ip_nat_protocol *proto)
 {
         write_lock_bh(&ip_nat_lock);
-        ip_nat_protos[proto->protonum] = &ip_nat_unknown_protocol;
+        rcu_assign_pointer(ip_nat_protos[proto->protonum],
+                           &ip_nat_unknown_protocol);
         write_unlock_bh(&ip_nat_lock);
-
-        /* Someone could be still looking at the proto in a bh. */
-        synchronize_net();
+        synchronize_rcu();
 }
 EXPORT_SYMBOL(ip_nat_protocol_unregister);
 
@@ -594,10 +591,10 @@ static int __init ip_nat_init(void)
         /* Sew in builtin protocols. */
         write_lock_bh(&ip_nat_lock);
         for (i = 0; i < MAX_IP_NAT_PROTO; i++)
-                ip_nat_protos[i] = &ip_nat_unknown_protocol;
-        ip_nat_protos[IPPROTO_TCP] = &ip_nat_protocol_tcp;
-        ip_nat_protos[IPPROTO_UDP] = &ip_nat_protocol_udp;
-        ip_nat_protos[IPPROTO_ICMP] = &ip_nat_protocol_icmp;
+                rcu_assign_pointer(ip_nat_protos[i], &ip_nat_unknown_protocol);
+        rcu_assign_pointer(ip_nat_protos[IPPROTO_TCP], &ip_nat_protocol_tcp);
+        rcu_assign_pointer(ip_nat_protos[IPPROTO_UDP], &ip_nat_protocol_udp);
+        rcu_assign_pointer(ip_nat_protos[IPPROTO_ICMP], &ip_nat_protocol_icmp);
         write_unlock_bh(&ip_nat_lock);
 
         for (i = 0; i < ip_nat_htable_size; i++) {