[XFRM]: Fix aevent related crash

[Patrick McHardy]

Fix a regression in net-2.6.17 from the aevent patches.


[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 <[EMAIL PROTECTED]>

---
commit bee4457e500cbbe3f6d8a5b200588f6b0afb6f93
tree f174724ffb83f8a9768257d2ac320710f008002b
parent 5134e9a6559778d2f3f8dcaf60a1009360e477a2
author Patrick McHardy <[EMAIL PROTECTED]> Mon, 06 Mar 2006 14:14:30 +0100
committer Patrick McHardy <[EMAIL PROTECTED]> Mon, 06 Mar 2006 14:14:30 +0100

 include/net/xfrm.h   |   10 +++++++++-
 net/xfrm/xfrm_user.c |   11 ++++++++---
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 156f52e..7dff185 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -1000,7 +1000,15 @@ static inline int xfrm_policy_id2dir(u32
 
 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 ca8ac61..7afe4b1 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);
 
@@ -1962,6 +1965,8 @@ static int __init xfrm_user_init(void)
 static void __exit xfrm_user_exit(void)
 {
        xfrm_unregister_km(&netlink_mgr);
+       rcu_assign_pointer(xfrm_nl, NULL);
+       synchronize_rcu();
        sock_release(xfrm_nl->sk_socket);
 }