[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>

diff --git a/net/ipv4/netfilter/ip_nat_core.c b/net/ipv4/netfilter/ip_nat_core.c
index 275a4d3faf0af65d0da5ed7470d71d137dba30f5..85ae0cabc8b5cc4d90b4f4537f52814a0f0f5257 100644 (file)
--- 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++) {