Make sure listing doesn't grab a set which is just being destroyed.

There was a small window when all sets are destroyed and a concurrent
listing of all sets could grab a set which is just being destroyed.

diff --git a/kernel/net/netfilter/ipset/ip_set_core.c b/kernel/net/netfilter/ipset/ip_set_core.c
index ab4110a5f2c3a299747dc91b7a2369ced1189eb6..3808918c789ffc639a22554bd0b2080a86ec4b62 100644 (file)
--- a/kernel/net/netfilter/ipset/ip_set_core.c
+++ b/kernel/net/netfilter/ipset/ip_set_core.c
@@ -32,7 +32,8 @@ static DEFINE_RWLOCK(ip_set_ref_lock);                /* protects the set refs */
 struct ip_set_net {
        struct ip_set * __rcu *ip_set_list;     /* all individual sets */
        ip_set_id_t     ip_set_max;     /* max number of sets */
-       int             is_deleted;     /* deleted by ip_set_net_exit */
+       bool            is_deleted;     /* deleted by ip_set_net_exit */
+       bool            is_destroyed;   /* all sets are destroyed */
 };
 
 static int ip_set_net_id __read_mostly;
@@ -983,12 +984,15 @@ ip_set_destroy(struct sock *ctnl, struct sk_buff *skb,
                                goto out;
                        }
                }
+               inst->is_destroyed = true;
                read_unlock_bh(&ip_set_ref_lock);
                for (i = 0; i < inst->ip_set_max; i++) {
                        s = ip_set(inst, i);
                        if (s != NULL)
                                ip_set_destroy_set(inst, i);
                }
+               /* Modified by ip_set_destroy() only, which is serialized */
+               inst->is_destroyed = false;
        } else {
                s = find_set_and_id(inst, nla_data(attr[IPSET_ATTR_SETNAME]),
                                    &i);
@@ -1271,12 +1275,19 @@ dump_last:
                 dump_type, dump_flags, cb->args[IPSET_CB_INDEX]);
        for (; cb->args[IPSET_CB_INDEX] < max; cb->args[IPSET_CB_INDEX]++) {
                index = (ip_set_id_t)cb->args[IPSET_CB_INDEX];
+               write_lock_bh(&ip_set_ref_lock);
                set = ip_set(inst, index);
-               if (set == NULL) {
+               if (set == NULL || inst->is_destroyed) {
+                       write_unlock_bh(&ip_set_ref_lock);
                        if (dump_type == DUMP_ONE) {
                                ret = -ENOENT;
                                goto out;
                        }
+                       if (inst->is_destroyed) {
+                               /* All sets are just being destroyed */
+                               ret = 0;
+                               goto out;
+                       }
                        continue;
                }
                /* When dumping all sets, we must dump "sorted"
@@ -1284,14 +1295,17 @@ dump_last:
                 */
                if (dump_type != DUMP_ONE &&
                    ((dump_type == DUMP_ALL) ==
-                    !!(set->type->features & IPSET_DUMP_LAST)))
+                    !!(set->type->features & IPSET_DUMP_LAST))) {
+                       write_unlock_bh(&ip_set_ref_lock);
                        continue;
+               }
                pr_debug("List set: %s\n", set->name);
                if (!cb->args[IPSET_CB_ARG0]) {
                        /* Start listing: make sure set won't be destroyed */
                        pr_debug("reference set\n");
-                       __ip_set_get(set);
+                       set->ref++;
                }
+               write_unlock_bh(&ip_set_ref_lock);
                nlh = start_msg(skb, NETLINK_PORTID(cb->skb),
                                cb->nlh->nlmsg_seq, flags,
                                IPSET_CMD_LIST);
@@ -2000,7 +2014,8 @@ ip_set_net_init(struct net *net)
 #else
                goto err_alloc;
 #endif
-       inst->is_deleted = 0;
+       inst->is_deleted = false;
+       inst->is_destroyed = false;
        rcu_assign_pointer(inst->ip_set_list, list);
        return 0;
 
@@ -2019,7 +2034,7 @@ ip_set_net_exit(struct net *net)
        struct ip_set *set = NULL;
        ip_set_id_t i;
 
-       inst->is_deleted = 1; /* flag for ip_set_nfnl_put */
+       inst->is_deleted = true; /* flag for ip_set_nfnl_put */
 
        for (i = 0; i < inst->ip_set_max; i++) {
                set = ip_set(inst, i);