[NETFILTER]: nf_nat: properly use RCU API for nf_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, 28 insertions, 31 deletions

diff --git a/net/ipv4/netfilter/nf_nat_core.c b/net/ipv4/netfilter/nf_nat_core.c
index cf1010827be1..6d0061f05810 100644
--- a/net/ipv4/netfilter/nf_nat_core.c
+++ b/net/ipv4/netfilter/nf_nat_core.c
@@ -53,7 +53,7 @@ static struct nf_nat_protocol *nf_nat_protos[MAX_IP_NAT_PROTO];
 static inline struct nf_nat_protocol *
 __nf_nat_proto_find(u_int8_t protonum)
 {
-        return nf_nat_protos[protonum];
+        return rcu_dereference(nf_nat_protos[protonum]);
 }
 
 struct nf_nat_protocol *
@@ -61,13 +61,11 @@ nf_nat_proto_find_get(u_int8_t protonum)
 {
         struct nf_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 = __nf_nat_proto_find(protonum);
         if (!try_module_get(p->me))
                 p = &nf_nat_unknown_protocol;
-        preempt_enable();
+        rcu_read_unlock();
 
         return p;
 }
@@ -126,8 +124,8 @@ in_range(const struct nf_conntrack_tuple *tuple,
          const struct nf_nat_range *range)
 {
         struct nf_nat_protocol *proto;
+        int ret = 0;
 
-        proto = __nf_nat_proto_find(tuple->dst.protonum);
         /* 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. */
         if (range->flags & IP_NAT_RANGE_MAP_IPS) {
@@ -136,12 +134,15 @@ in_range(const struct nf_conntrack_tuple *tuple,
                         return 0;
         }
 
+        rcu_read_lock();
+        proto = __nf_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
@@ -268,27 +269,25 @@ get_unique_tuple(struct nf_conntrack_tuple *tuple,
         /* 3) The per-protocol part of the manip is made to map into
            the range to make a unique tuple. */
 
-        proto = nf_nat_proto_find_get(orig_tuple->dst.protonum);
+        rcu_read_lock();
+        proto = __nf_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, ct);
-                nf_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)) &&
-            !nf_nat_used_tuple(tuple, ct)) {
-                nf_nat_proto_put(proto);
-                return;
-        }
+            !nf_nat_used_tuple(tuple, ct))
+                goto out;
 
         /* Last change: get protocol to try to obtain unique tuple. */
         proto->unique_tuple(tuple, range, maniptype, ct);
-
-        nf_nat_proto_put(proto);
+out:
+        rcu_read_unlock();
 }
 
 unsigned int
@@ -369,12 +368,11 @@ manip_pkt(u_int16_t proto,
         iph = (void *)(*pskb)->data + iphdroff;
 
         /* Manipulate protcol part. */
-        p = nf_nat_proto_find_get(proto);
-        if (!p->manip_pkt(pskb, iphdroff, target, maniptype)) {
-                nf_nat_proto_put(p);
+
+        /* rcu_read_lock()ed by nf_hook_slow */
+        p = __nf_nat_proto_find(proto);
+        if (!p->manip_pkt(pskb, iphdroff, target, maniptype))
                 return 0;
-        }
-        nf_nat_proto_put(p);
 
         iph = (void *)(*pskb)->data + iphdroff;
 
@@ -529,7 +527,7 @@ int nf_nat_protocol_register(struct nf_nat_protocol *proto)
                 ret = -EBUSY;
                 goto out;
         }
-        nf_nat_protos[proto->protonum] = proto;
+        rcu_assign_pointer(nf_nat_protos[proto->protonum], proto);
  out:
         write_unlock_bh(&nf_nat_lock);
         return ret;
@@ -540,11 +538,10 @@ EXPORT_SYMBOL(nf_nat_protocol_register);
 void nf_nat_protocol_unregister(struct nf_nat_protocol *proto)
 {
         write_lock_bh(&nf_nat_lock);
-        nf_nat_protos[proto->protonum] = &nf_nat_unknown_protocol;
+        rcu_assign_pointer(nf_nat_protos[proto->protonum],
+                           &nf_nat_unknown_protocol);
         write_unlock_bh(&nf_nat_lock);
-
-        /* Someone could be still looking at the proto in a bh. */
-        synchronize_net();
+        synchronize_rcu();
 }
 EXPORT_SYMBOL(nf_nat_protocol_unregister);
 
@@ -608,10 +605,10 @@ static int __init nf_nat_init(void)
         /* Sew in builtin protocols. */
         write_lock_bh(&nf_nat_lock);
         for (i = 0; i < MAX_IP_NAT_PROTO; i++)
-                nf_nat_protos[i] = &nf_nat_unknown_protocol;
-        nf_nat_protos[IPPROTO_TCP] = &nf_nat_protocol_tcp;
-        nf_nat_protos[IPPROTO_UDP] = &nf_nat_protocol_udp;
-        nf_nat_protos[IPPROTO_ICMP] = &nf_nat_protocol_icmp;
+                rcu_assign_pointer(nf_nat_protos[i], &nf_nat_unknown_protocol);
+        rcu_assign_pointer(nf_nat_protos[IPPROTO_TCP], &nf_nat_protocol_tcp);
+        rcu_assign_pointer(nf_nat_protos[IPPROTO_UDP], &nf_nat_protocol_udp);
+        rcu_assign_pointer(nf_nat_protos[IPPROTO_ICMP], &nf_nat_protocol_icmp);
         write_unlock_bh(&nf_nat_lock);
 
         for (i = 0; i < nf_nat_htable_size; i++) {