ip6mr: Make mroute_sk rcu-based

In ipmr the mr_table socket is handled under RCU. Introduce the same
for ip6mr.

Signed-off-by: Yuval Mintz <yuvalm@mellanox.com>
Acked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 31 insertions, 22 deletions

diff --git a/include/linux/mroute6.h b/include/linux/mroute6.h
index e5e5b8282551..e1b9fb06e1ea 100644
--- a/include/linux/mroute6.h
+++ b/include/linux/mroute6.h
@@ -111,12 +111,12 @@ extern int ip6mr_get_route(struct net *net, struct sk_buff *skb,
                            struct rtmsg *rtm, u32 portid);
 
 #ifdef CONFIG_IPV6_MROUTE
-extern struct sock *mroute6_socket(struct net *net, struct sk_buff *skb);
+bool mroute6_is_socket(struct net *net, struct sk_buff *skb);
 extern int ip6mr_sk_done(struct sock *sk);
 #else
-static inline struct sock *mroute6_socket(struct net *net, struct sk_buff *skb)
+static inline bool mroute6_is_socket(struct net *net, struct sk_buff *skb)
 {
-        return NULL;
+        return false;
 }
 static inline int ip6mr_sk_done(struct sock *sk)
 {
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 997c7f19ad62..a6eb0e699b15 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -71,7 +71,7 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff *
                 struct inet6_dev *idev = ip6_dst_idev(skb_dst(skb));
 
                 if (!(dev->flags & IFF_LOOPBACK) && sk_mc_loop(sk) &&
-                    ((mroute6_socket(net, skb) &&
+                    ((mroute6_is_socket(net, skb) &&
                      !(IP6CB(skb)->flags & IP6SKB_FORWARDED)) ||
                      ipv6_chk_mcast_addr(dev, &ipv6_hdr(skb)->daddr,
                                          &ipv6_hdr(skb)->saddr))) {
diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index e397990f6eb8..a0e297ddca6e 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -58,7 +58,7 @@ struct mr6_table {
         struct list_head        list;
         possible_net_t          net;
         u32                     id;
-        struct sock             *mroute6_sk;
+        struct sock __rcu       *mroute6_sk;
         struct timer_list       ipmr_expire_timer;
         struct list_head        mfc6_unres_queue;
         struct list_head        mfc6_cache_array[MFC6_LINES];
@@ -1121,6 +1121,7 @@ static void ip6mr_cache_resolve(struct net *net, struct mr6_table *mrt,
 static int ip6mr_cache_report(struct mr6_table *mrt, struct sk_buff *pkt,
                               mifi_t mifi, int assert)
 {
+        struct sock *mroute6_sk;
         struct sk_buff *skb;
         struct mrt6msg *msg;
         int ret;
@@ -1190,17 +1191,19 @@ static int ip6mr_cache_report(struct mr6_table *mrt, struct sk_buff *pkt,
         skb->ip_summed = CHECKSUM_UNNECESSARY;
         }
 
-        if (!mrt->mroute6_sk) {
+        rcu_read_lock();
+        mroute6_sk = rcu_dereference(mrt->mroute6_sk);
+        if (!mroute6_sk) {
+                rcu_read_unlock();
                 kfree_skb(skb);
                 return -EINVAL;
         }
 
         mrt6msg_netlink_event(mrt, skb);
 
-        /*
-         *      Deliver to user space multicast routing algorithms
-         */
-        ret = sock_queue_rcv_skb(mrt->mroute6_sk, skb);
+        /* Deliver to user space multicast routing algorithms */
+        ret = sock_queue_rcv_skb(mroute6_sk, skb);
+        rcu_read_unlock();
         if (ret < 0) {
                 net_warn_ratelimited("mroute6: pending queue full, dropping entries\n");
                 kfree_skb(skb);
@@ -1584,11 +1587,11 @@ static int ip6mr_sk_init(struct mr6_table *mrt, struct sock *sk)
 
         rtnl_lock();
         write_lock_bh(&mrt_lock);
-        if (likely(mrt->mroute6_sk == NULL)) {
-                mrt->mroute6_sk = sk;
-                net->ipv6.devconf_all->mc_forwarding++;
-        } else {
+        if (rtnl_dereference(mrt->mroute6_sk)) {
                 err = -EADDRINUSE;
+        } else {
+                rcu_assign_pointer(mrt->mroute6_sk, sk);
+                net->ipv6.devconf_all->mc_forwarding++;
         }
         write_unlock_bh(&mrt_lock);
 
@@ -1614,9 +1617,9 @@ int ip6mr_sk_done(struct sock *sk)
 
         rtnl_lock();
         ip6mr_for_each_table(mrt, net) {
-                if (sk == mrt->mroute6_sk) {
+                if (sk == rtnl_dereference(mrt->mroute6_sk)) {
                         write_lock_bh(&mrt_lock);
-                        mrt->mroute6_sk = NULL;
+                        RCU_INIT_POINTER(mrt->mroute6_sk, NULL);
                         net->ipv6.devconf_all->mc_forwarding--;
                         write_unlock_bh(&mrt_lock);
                         inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,
@@ -1630,11 +1633,12 @@ int ip6mr_sk_done(struct sock *sk)
                 }
         }
         rtnl_unlock();
+        synchronize_rcu();
 
         return err;
 }
 
-struct sock *mroute6_socket(struct net *net, struct sk_buff *skb)
+bool mroute6_is_socket(struct net *net, struct sk_buff *skb)
 {
         struct mr6_table *mrt;
         struct flowi6 fl6 = {
@@ -1646,8 +1650,9 @@ struct sock *mroute6_socket(struct net *net, struct sk_buff *skb)
         if (ip6mr_fib_lookup(net, &fl6, &mrt) < 0)
                 return NULL;
 
-        return mrt->mroute6_sk;
+        return rcu_access_pointer(mrt->mroute6_sk);
 }
+EXPORT_SYMBOL(mroute6_is_socket);
 
 /*
  *      Socket options and virtual interface manipulation. The whole
@@ -1674,7 +1679,8 @@ int ip6_mroute_setsockopt(struct sock *sk, int optname, char __user *optval, uns
                 return -ENOENT;
 
         if (optname != MRT6_INIT) {
-                if (sk != mrt->mroute6_sk && !ns_capable(net->user_ns, CAP_NET_ADMIN))
+                if (sk != rcu_access_pointer(mrt->mroute6_sk) &&
+                    !ns_capable(net->user_ns, CAP_NET_ADMIN))
                         return -EACCES;
         }
 
@@ -1696,7 +1702,8 @@ int ip6_mroute_setsockopt(struct sock *sk, int optname, char __user *optval, uns
                 if (vif.mif6c_mifi >= MAXMIFS)
                         return -ENFILE;
                 rtnl_lock();
-                ret = mif6_add(net, mrt, &vif, sk == mrt->mroute6_sk);
+                ret = mif6_add(net, mrt, &vif,
+                               sk == rtnl_dereference(mrt->mroute6_sk));
                 rtnl_unlock();
                 return ret;
 
@@ -1731,7 +1738,9 @@ int ip6_mroute_setsockopt(struct sock *sk, int optname, char __user *optval, uns
                         ret = ip6mr_mfc_delete(mrt, &mfc, parent);
                 else
                         ret = ip6mr_mfc_add(net, mrt, &mfc,
-                                            sk == mrt->mroute6_sk, parent);
+                                            sk ==
+                                            rtnl_dereference(mrt->mroute6_sk),
+                                            parent);
                 rtnl_unlock();
                 return ret;
 
@@ -1783,7 +1792,7 @@ int ip6_mroute_setsockopt(struct sock *sk, int optname, char __user *optval, uns
                 /* "pim6reg%u" should not exceed 16 bytes (IFNAMSIZ) */
                 if (v != RT_TABLE_DEFAULT && v >= 100000000)
                         return -EINVAL;
-                if (sk == mrt->mroute6_sk)
+                if (sk == rcu_access_pointer(mrt->mroute6_sk))
                         return -EBUSY;
 
                 rtnl_lock();