[NETFILTER]: ip_conntrack: properly use RCU API for ip_ct_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
all paths not obviously only used within packet process context
(nfnetlink_conntrack).

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

3 files changed, 26 insertions, 15 deletions

diff --git a/net/ipv4/netfilter/ip_conntrack_core.c b/net/ipv4/netfilter/ip_conntrack_core.c
index 508e6007a191..e7de6d31b853 100644
--- a/net/ipv4/netfilter/ip_conntrack_core.c
+++ b/net/ipv4/netfilter/ip_conntrack_core.c
@@ -318,9 +318,11 @@ destroy_conntrack(struct nf_conntrack *nfct)
         /* To make sure we don't get any weird locking issues here:
          * destroy_conntrack() MUST NOT be called with a write lock
          * to ip_conntrack_lock!!! -HW */
+        rcu_read_lock();
         proto = __ip_conntrack_proto_find(ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.protonum);
         if (proto && proto->destroy)
                 proto->destroy(ct);
+        rcu_read_unlock();
 
         if (ip_conntrack_destroyed)
                 ip_conntrack_destroyed(ct);
@@ -595,13 +597,13 @@ ip_conntrack_proto_find_get(u_int8_t protocol)
 {
         struct ip_conntrack_protocol *p;
 
-        preempt_disable();
+        rcu_read_lock();
         p = __ip_conntrack_proto_find(protocol);
         if (p) {
                 if (!try_module_get(p->me))
                         p = &ip_conntrack_generic_protocol;
         }
-        preempt_enable();
+        rcu_read_unlock();
 
         return p;
 }
@@ -830,6 +832,7 @@ unsigned int ip_conntrack_in(unsigned int hooknum,
         }
 #endif
 
+        /* rcu_read_lock()ed by nf_hook_slow */
         proto = __ip_conntrack_proto_find((*pskb)->nh.iph->protocol);
 
         /* It may be an special packet, error, unclean...
@@ -875,8 +878,15 @@ unsigned int ip_conntrack_in(unsigned int hooknum,
 int invert_tuplepr(struct ip_conntrack_tuple *inverse,
                    const struct ip_conntrack_tuple *orig)
 {
-        return ip_ct_invert_tuple(inverse, orig,
-                                  __ip_conntrack_proto_find(orig->dst.protonum));
+        struct ip_conntrack_protocol *proto;
+        int ret;
+
+        rcu_read_lock();
+        proto = __ip_conntrack_proto_find(orig->dst.protonum);
+        ret = ip_ct_invert_tuple(inverse, orig, proto);
+        rcu_read_unlock();
+
+        return ret;
 }
 
 /* Would two expected things clash? */
@@ -1507,11 +1517,11 @@ int __init ip_conntrack_init(void)
         /* Don't NEED lock here, but good form anyway. */
         write_lock_bh(&ip_conntrack_lock);
         for (i = 0; i < MAX_IP_CT_PROTO; i++)
-                ip_ct_protos[i] = &ip_conntrack_generic_protocol;
+                rcu_assign_pointer(ip_ct_protos[i], &ip_conntrack_generic_protocol);
         /* Sew in builtin protocols. */
-        ip_ct_protos[IPPROTO_TCP] = &ip_conntrack_protocol_tcp;
-        ip_ct_protos[IPPROTO_UDP] = &ip_conntrack_protocol_udp;
-        ip_ct_protos[IPPROTO_ICMP] = &ip_conntrack_protocol_icmp;
+        rcu_assign_pointer(ip_ct_protos[IPPROTO_TCP], &ip_conntrack_protocol_tcp);
+        rcu_assign_pointer(ip_ct_protos[IPPROTO_UDP], &ip_conntrack_protocol_udp);
+        rcu_assign_pointer(ip_ct_protos[IPPROTO_ICMP], &ip_conntrack_protocol_icmp);
         write_unlock_bh(&ip_conntrack_lock);
 
         /* For use by ipt_REJECT */
diff --git a/net/ipv4/netfilter/ip_conntrack_standalone.c b/net/ipv4/netfilter/ip_conntrack_standalone.c
index 300ccbbbdac9..c7c1ec61b0f5 100644
--- a/net/ipv4/netfilter/ip_conntrack_standalone.c
+++ b/net/ipv4/netfilter/ip_conntrack_standalone.c
@@ -796,7 +796,7 @@ int ip_conntrack_protocol_register(struct ip_conntrack_protocol *proto)
                 ret = -EBUSY;
                 goto out;
         }
-        ip_ct_protos[proto->proto] = proto;
+        rcu_assign_pointer(ip_ct_protos[proto->proto], proto);
  out:
         write_unlock_bh(&ip_conntrack_lock);
         return ret;
@@ -805,11 +805,10 @@ int ip_conntrack_protocol_register(struct ip_conntrack_protocol *proto)
 void ip_conntrack_protocol_unregister(struct ip_conntrack_protocol *proto)
 {
         write_lock_bh(&ip_conntrack_lock);
-        ip_ct_protos[proto->proto] = &ip_conntrack_generic_protocol;
+        rcu_assign_pointer(ip_ct_protos[proto->proto],
+                           &ip_conntrack_generic_protocol);
         write_unlock_bh(&ip_conntrack_lock);
-
-        /* Somebody could be still looking at the proto in bh. */
-        synchronize_net();
+        synchronize_rcu();
 
         /* Remove all contrack entries for this protocol */
         ip_ct_iterate_cleanup(kill_proto, &proto->proto);
diff --git a/net/ipv4/netfilter/ip_nat_core.c b/net/ipv4/netfilter/ip_nat_core.c
index 85ae0cabc8b5..18daabc22069 100644
--- a/net/ipv4/netfilter/ip_nat_core.c
+++ b/net/ipv4/netfilter/ip_nat_core.c
@@ -420,6 +420,7 @@ int ip_nat_icmp_reply_translation(struct ip_conntrack *ct,
                 struct icmphdr icmp;
                 struct iphdr ip;
         } *inside;
+        struct ip_conntrack_protocol *proto;
         struct ip_conntrack_tuple inner, target;
         int hdrlen = (*pskb)->nh.iph->ihl * 4;
         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
@@ -455,10 +456,11 @@ int ip_nat_icmp_reply_translation(struct ip_conntrack *ct,
         DEBUGP("icmp_reply_translation: translating error %p manp %u dir %s\n",
                *pskb, manip, dir == IP_CT_DIR_ORIGINAL ? "ORIG" : "REPLY");
 
+        /* rcu_read_lock()ed by nf_hook_slow */
+        proto = __ip_conntrack_proto_find(inside->ip.protocol);
         if (!ip_ct_get_tuple(&inside->ip, *pskb, (*pskb)->nh.iph->ihl*4 +
                              sizeof(struct icmphdr) + inside->ip.ihl*4,
-                             &inner,
-                             __ip_conntrack_proto_find(inside->ip.protocol)))
+                             &inner, proto))
                 return 0;
 
         /* Change inner back to look like incoming packet.  We do the