vxlan: avoid using stale vxlan socket.

When vxlan device is closed vxlan socket is freed. This
operation can race with vxlan-xmit function which
dereferences vxlan socket. Following patch uses RCU
mechanism to avoid this situation.

Signed-off-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index c1639a3..f3c2fa3 100644 (file)
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -943,17 +943,20 @@ static bool vxlan_snoop(struct net_device *dev,
 static bool vxlan_group_used(struct vxlan_net *vn, struct vxlan_dev *dev)
 {
        struct vxlan_dev *vxlan;
+       struct vxlan_sock *sock4;
+       struct vxlan_sock *sock6 = NULL;
        unsigned short family = dev->default_dst.remote_ip.sa.sa_family;
 
+       sock4 = rtnl_dereference(dev->vn4_sock);
+
        /* The vxlan_sock is only used by dev, leaving group has
         * no effect on other vxlan devices.
         */
-       if (family == AF_INET && dev->vn4_sock &&
-           atomic_read(&dev->vn4_sock->refcnt) == 1)
+       if (family == AF_INET && sock4 && atomic_read(&sock4->refcnt) == 1)
                return false;
 #if IS_ENABLED(CONFIG_IPV6)
-       if (family == AF_INET6 && dev->vn6_sock &&
-           atomic_read(&dev->vn6_sock->refcnt) == 1)
+       sock6 = rtnl_dereference(dev->vn6_sock);
+       if (family == AF_INET6 && sock6 && atomic_read(&sock6->refcnt) == 1)
                return false;
 #endif
 
@@ -961,10 +964,12 @@ static bool vxlan_group_used(struct vxlan_net *vn, struct vxlan_dev *dev)
                if (!netif_running(vxlan->dev) || vxlan == dev)
                        continue;
 
-               if (family == AF_INET && vxlan->vn4_sock != dev->vn4_sock)
+               if (family == AF_INET &&
+                   rtnl_dereference(vxlan->vn4_sock) != sock4)
                        continue;
 #if IS_ENABLED(CONFIG_IPV6)
-               if (family == AF_INET6 && vxlan->vn6_sock != dev->vn6_sock)
+               if (family == AF_INET6 &&
+                   rtnl_dereference(vxlan->vn6_sock) != sock6)
                        continue;
 #endif
 
@@ -1005,22 +1010,25 @@ static bool __vxlan_sock_release_prep(struct vxlan_sock *vs)
 
 static void vxlan_sock_release(struct vxlan_dev *vxlan)
 {
-       bool ipv4 = __vxlan_sock_release_prep(vxlan->vn4_sock);
+       struct vxlan_sock *sock4 = rtnl_dereference(vxlan->vn4_sock);
 #if IS_ENABLED(CONFIG_IPV6)
-       bool ipv6 = __vxlan_sock_release_prep(vxlan->vn6_sock);
+       struct vxlan_sock *sock6 = rtnl_dereference(vxlan->vn6_sock);
+
+       rcu_assign_pointer(vxlan->vn6_sock, NULL);
 #endif
 
+       rcu_assign_pointer(vxlan->vn4_sock, NULL);
        synchronize_net();
 
-       if (ipv4) {
-               udp_tunnel_sock_release(vxlan->vn4_sock->sock);
-               kfree(vxlan->vn4_sock);
+       if (__vxlan_sock_release_prep(sock4)) {
+               udp_tunnel_sock_release(sock4->sock);
+               kfree(sock4);
        }
 
 #if IS_ENABLED(CONFIG_IPV6)
-       if (ipv6) {
-               udp_tunnel_sock_release(vxlan->vn6_sock->sock);
-               kfree(vxlan->vn6_sock);
+       if (__vxlan_sock_release_prep(sock6)) {
+               udp_tunnel_sock_release(sock6->sock);
+               kfree(sock6);
        }
 #endif
 }
@@ -1036,18 +1044,21 @@ static int vxlan_igmp_join(struct vxlan_dev *vxlan)
        int ret = -EINVAL;
 
        if (ip->sa.sa_family == AF_INET) {
+               struct vxlan_sock *sock4 = rtnl_dereference(vxlan->vn4_sock);
                struct ip_mreqn mreq = {
                        .imr_multiaddr.s_addr   = ip->sin.sin_addr.s_addr,
                        .imr_ifindex            = ifindex,
                };
 
-               sk = vxlan->vn4_sock->sock->sk;
+               sk = sock4->sock->sk;
                lock_sock(sk);
                ret = ip_mc_join_group(sk, &mreq);
                release_sock(sk);
 #if IS_ENABLED(CONFIG_IPV6)
        } else {
-               sk = vxlan->vn6_sock->sock->sk;
+               struct vxlan_sock *sock6 = rtnl_dereference(vxlan->vn6_sock);
+
+               sk = sock6->sock->sk;
                lock_sock(sk);
                ret = ipv6_stub->ipv6_sock_mc_join(sk, ifindex,
                                                   &ip->sin6.sin6_addr);
@@ -1067,18 +1078,21 @@ static int vxlan_igmp_leave(struct vxlan_dev *vxlan)
        int ret = -EINVAL;
 
        if (ip->sa.sa_family == AF_INET) {
+               struct vxlan_sock *sock4 = rtnl_dereference(vxlan->vn4_sock);
                struct ip_mreqn mreq = {
                        .imr_multiaddr.s_addr   = ip->sin.sin_addr.s_addr,
                        .imr_ifindex            = ifindex,
                };
 
-               sk = vxlan->vn4_sock->sock->sk;
+               sk = sock4->sock->sk;
                lock_sock(sk);
                ret = ip_mc_leave_group(sk, &mreq);
                release_sock(sk);
 #if IS_ENABLED(CONFIG_IPV6)
        } else {
-               sk = vxlan->vn6_sock->sock->sk;
+               struct vxlan_sock *sock6 = rtnl_dereference(vxlan->vn6_sock);
+
+               sk = sock6->sock->sk;
                lock_sock(sk);
                ret = ipv6_stub->ipv6_sock_mc_drop(sk, ifindex,
                                                   &ip->sin6.sin6_addr);
@@ -1828,11 +1842,15 @@ static struct dst_entry *vxlan6_get_route(struct vxlan_dev *vxlan,
                                          struct dst_cache *dst_cache,
                                          const struct ip_tunnel_info *info)
 {
+       struct vxlan_sock *sock6 = rcu_dereference(vxlan->vn6_sock);
        bool use_cache = ip_tunnel_dst_cache_usable(skb, info);
        struct dst_entry *ndst;
        struct flowi6 fl6;
        int err;
 
+       if (!sock6)
+               return ERR_PTR(-EIO);
+
        if (tos && !info)
                use_cache = false;
        if (use_cache) {
@@ -1850,7 +1868,7 @@ static struct dst_entry *vxlan6_get_route(struct vxlan_dev *vxlan,
        fl6.flowi6_proto = IPPROTO_UDP;
 
        err = ipv6_stub->ipv6_dst_lookup(vxlan->net,
-                                        vxlan->vn6_sock->sock->sk,
+                                        sock6->sock->sk,
                                         &ndst, &fl6);
        if (err < 0)
                return ERR_PTR(err);
@@ -1995,9 +2013,11 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
        }
 
        if (dst->sa.sa_family == AF_INET) {
-               if (!vxlan->vn4_sock)
+               struct vxlan_sock *sock4 = rcu_dereference(vxlan->vn4_sock);
+
+               if (!sock4)
                        goto drop;
-               sk = vxlan->vn4_sock->sock->sk;
+               sk = sock4->sock->sk;
 
                rt = vxlan_get_route(vxlan, skb,
                                     rdst ? rdst->remote_ifindex : 0, tos,
@@ -2050,12 +2070,13 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
                                    src_port, dst_port, xnet, !udp_sum);
 #if IS_ENABLED(CONFIG_IPV6)
        } else {
+               struct vxlan_sock *sock6 = rcu_dereference(vxlan->vn6_sock);
                struct dst_entry *ndst;
                u32 rt6i_flags;
 
-               if (!vxlan->vn6_sock)
+               if (!sock6)
                        goto drop;
-               sk = vxlan->vn6_sock->sock->sk;
+               sk = sock6->sock->sk;
 
                ndst = vxlan6_get_route(vxlan, skb,
                                        rdst ? rdst->remote_ifindex : 0, tos,
@@ -2415,9 +2436,10 @@ static int vxlan_fill_metadata_dst(struct net_device *dev, struct sk_buff *skb)
        dport = info->key.tp_dst ? : vxlan->cfg.dst_port;
 
        if (ip_tunnel_info_af(info) == AF_INET) {
+               struct vxlan_sock *sock4 = rcu_dereference(vxlan->vn4_sock);
                struct rtable *rt;
 
-               if (!vxlan->vn4_sock)
+               if (!sock4)
                        return -EINVAL;
                rt = vxlan_get_route(vxlan, skb, 0, info->key.tos,
                                     info->key.u.ipv4.dst,
@@ -2429,8 +2451,6 @@ static int vxlan_fill_metadata_dst(struct net_device *dev, struct sk_buff *skb)
 #if IS_ENABLED(CONFIG_IPV6)
                struct dst_entry *ndst;
 
-               if (!vxlan->vn6_sock)
-                       return -EINVAL;
                ndst = vxlan6_get_route(vxlan, skb, 0, info->key.tos,
                                        info->key.label, &info->key.u.ipv6.dst,
                                        &info->key.u.ipv6.src, NULL, info);
@@ -2740,10 +2760,10 @@ static int __vxlan_sock_add(struct vxlan_dev *vxlan, bool ipv6)
                return PTR_ERR(vs);
 #if IS_ENABLED(CONFIG_IPV6)
        if (ipv6)
-               vxlan->vn6_sock = vs;
+               rcu_assign_pointer(vxlan->vn6_sock, vs);
        else
 #endif
-               vxlan->vn4_sock = vs;
+               rcu_assign_pointer(vxlan->vn4_sock, vs);
        vxlan_vs_add_dev(vs, vxlan);
        return 0;
 }
@@ -2754,9 +2774,9 @@ static int vxlan_sock_add(struct vxlan_dev *vxlan)
        bool metadata = vxlan->flags & VXLAN_F_COLLECT_METADATA;
        int ret = 0;
 
-       vxlan->vn4_sock = NULL;
+       RCU_INIT_POINTER(vxlan->vn4_sock, NULL);
 #if IS_ENABLED(CONFIG_IPV6)
-       vxlan->vn6_sock = NULL;
+       RCU_INIT_POINTER(vxlan->vn6_sock, NULL);
        if (ipv6 || metadata)
                ret = __vxlan_sock_add(vxlan, true);
 #endif

diff --git a/include/net/vxlan.h b/include/net/vxlan.h
index 0255613..308adc4 100644 (file)
--- a/include/net/vxlan.h
+++ b/include/net/vxlan.h
@@ -225,9 +225,9 @@ struct vxlan_config {
 struct vxlan_dev {
        struct hlist_node hlist;        /* vni hash table */
        struct list_head  next;         /* vxlan's per namespace list */
-       struct vxlan_sock *vn4_sock;    /* listening socket for IPv4 */
+       struct vxlan_sock __rcu *vn4_sock;      /* listening socket for IPv4 */
 #if IS_ENABLED(CONFIG_IPV6)
-       struct vxlan_sock *vn6_sock;    /* listening socket for IPv6 */
+       struct vxlan_sock __rcu *vn6_sock;      /* listening socket for IPv6 */
 #endif
        struct net_device *dev;
        struct net        *net;         /* netns for packet i/o */