[XFRM]: Fix aevent related crash

When xfrm_user isn't loaded xfrm_nl is NULL, which makes IPsec crash because
xfrm_aevent_is_on passes the NULL pointer to netlink_has_listeners as socket.
A second problem is that the xfrm_nl pointer is not cleared when the socket
is releases at module unload time.

Protect references of xfrm_nl from outside of xfrm_user by RCU, check
that the socket is present in xfrm_aevent_is_on and set it to NULL
when unloading xfrm_user.

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

2 files changed, 20 insertions, 5 deletions

diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 786371365f2b..61b7504fc2ba 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -1001,7 +1001,15 @@ static inline int xfrm_policy_id2dir(u32 index)
 
 static inline int xfrm_aevent_is_on(void)
 {
-        return netlink_has_listeners(xfrm_nl,XFRMNLGRP_AEVENTS);
+        struct sock *nlsk;
+        int ret = 0;
+
+        rcu_read_lock();
+        nlsk = rcu_dereference(xfrm_nl);
+        if (nlsk)
+                ret = netlink_has_listeners(nlsk, XFRMNLGRP_AEVENTS);
+        rcu_read_unlock();
+        return ret;
 }
 
 static inline void xfrm_aevent_doreplay(struct xfrm_state *x)
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 4a7120a7e10f..81d1005830f4 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1947,12 +1947,15 @@ static struct xfrm_mgr netlink_mgr = {
 
 static int __init xfrm_user_init(void)
 {
+        struct sock *nlsk;
+
         printk(KERN_INFO "Initializing IPsec netlink socket\n");
 
-        xfrm_nl = netlink_kernel_create(NETLINK_XFRM, XFRMNLGRP_MAX,
-                                        xfrm_netlink_rcv, THIS_MODULE);
-        if (xfrm_nl == NULL)
+        nlsk = netlink_kernel_create(NETLINK_XFRM, XFRMNLGRP_MAX,
+                                     xfrm_netlink_rcv, THIS_MODULE);
+        if (nlsk == NULL)
                 return -ENOMEM;
+        rcu_assign_pointer(xfrm_nl, nlsk);
 
         xfrm_register_km(&netlink_mgr);
 
@@ -1961,8 +1964,12 @@ static int __init xfrm_user_init(void)
 
 static void __exit xfrm_user_exit(void)
 {
+        struct sock *nlsk = xfrm_nl;
+
         xfrm_unregister_km(&netlink_mgr);
-        sock_release(xfrm_nl->sk_socket);
+        rcu_assign_pointer(xfrm_nl, NULL);
+        synchronize_rcu();
+        sock_release(nlsk->sk_socket);
 }
 
 module_init(xfrm_user_init);