[NETFILTER]: nf_conntrack: fix helper module unload races

[sfrench/cifs-2.6.git] / net / netfilter / nf_conntrack_netlink.c

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index d6d39e2413278b5b8fa9a60523be7a74ded14979..3f73327794ab40a7bb4ae05d0a8b3334458f9eea 100644 (file)
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -171,21 +171,29 @@ ctnetlink_dump_helpinfo(struct sk_buff *skb, const struct nf_conn *ct)
 {
        struct nfattr *nest_helper;
        const struct nf_conn_help *help = nfct_help(ct);
+       struct nf_conntrack_helper *helper;
 
-       if (!help || !help->helper)
+       if (!help)
                return 0;
 
+       rcu_read_lock();
+       helper = rcu_dereference(help->helper);
+       if (!helper)
+               goto out;
+
        nest_helper = NFA_NEST(skb, CTA_HELP);
-       NFA_PUT(skb, CTA_HELP_NAME, strlen(help->helper->name), help->helper->name);
+       NFA_PUT(skb, CTA_HELP_NAME, strlen(helper->name), helper->name);
 
-       if (help->helper->to_nfattr)
-               help->helper->to_nfattr(skb, ct);
+       if (helper->to_nfattr)
+               helper->to_nfattr(skb, ct);
 
        NFA_NEST_END(skb, nest_helper);
-
+out:
+       rcu_read_unlock();
        return 0;
 
 nfattr_failure:
+       rcu_read_unlock();
        return -1;
 }
 
@@ -842,7 +850,7 @@ ctnetlink_change_helper(struct nf_conn *ct, struct nfattr *cda[])
                if (help && help->helper) {
                        /* we had a helper before ... */
                        nf_ct_remove_expectations(ct);
-                       help->helper = NULL;
+                       rcu_assign_pointer(help->helper, NULL);
                }
 
                return 0;
@@ -866,7 +874,7 @@ ctnetlink_change_helper(struct nf_conn *ct, struct nfattr *cda[])
 
        /* need to zero data of old helper */
        memset(&help->help, 0, sizeof(help->help));
-       help->helper = helper;
+       rcu_assign_pointer(help->helper, helper);
 
        return 0;
 }
@@ -950,6 +958,7 @@ ctnetlink_create_conntrack(struct nfattr *cda[],
        struct nf_conn *ct;
        int err = -EINVAL;
        struct nf_conn_help *help;
+       struct nf_conntrack_helper *helper = NULL;
 
        ct = nf_conntrack_alloc(otuple, rtuple);
        if (ct == NULL || IS_ERR(ct))
@@ -980,14 +989,17 @@ ctnetlink_create_conntrack(struct nfattr *cda[],
 #endif
 
        help = nfct_help(ct);
-       if (help)
-               help->helper = nf_ct_helper_find_get(rtuple);
+       if (help) {
+               helper = nf_ct_helper_find_get(rtuple);
+               /* not in hash table yet so not strictly necessary */
+               rcu_assign_pointer(help->helper, helper);
+       }
 
        add_timer(&ct->timeout);
        nf_conntrack_hash_insert(ct);
 
-       if (help && help->helper)
-               nf_ct_helper_put(help->helper);
+       if (helper)
+               nf_ct_helper_put(helper);
 
        return 0;