netfilter: ipset: references are protected by rwlock instead of mutex

The timeout variant of the list:set type must reference the member sets.
However, its garbage collector runs at timer interrupt so the mutex
protection of the references is a no go. Therefore the reference protection
is converted to rwlock.

Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Signed-off-by: Patrick McHardy <kaber@trash.net>

5 files changed, 71 insertions, 53 deletions

diff --git a/net/netfilter/ipset/ip_set_bitmap_ip.c b/net/netfilter/ipset/ip_set_bitmap_ip.c
index bca96990218..a113ff06692 100644
--- a/net/netfilter/ipset/ip_set_bitmap_ip.c
+++ b/net/netfilter/ipset/ip_set_bitmap_ip.c
@@ -338,8 +338,7 @@ bitmap_ip_head(struct ip_set *set, struct sk_buff *skb)
         NLA_PUT_IPADDR4(skb, IPSET_ATTR_IP_TO, htonl(map->last_ip));
         if (map->netmask != 32)
                 NLA_PUT_U8(skb, IPSET_ATTR_NETMASK, map->netmask);
-        NLA_PUT_NET32(skb, IPSET_ATTR_REFERENCES,
-                      htonl(atomic_read(&set->ref) - 1));
+        NLA_PUT_NET32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref - 1));
         NLA_PUT_NET32(skb, IPSET_ATTR_MEMSIZE,
                       htonl(sizeof(*map) + map->memsize));
         if (with_timeout(map->timeout))
diff --git a/net/netfilter/ipset/ip_set_bitmap_ipmac.c b/net/netfilter/ipset/ip_set_bitmap_ipmac.c
index 5e790172def..00a33242e90 100644
--- a/net/netfilter/ipset/ip_set_bitmap_ipmac.c
+++ b/net/netfilter/ipset/ip_set_bitmap_ipmac.c
@@ -434,8 +434,7 @@ bitmap_ipmac_head(struct ip_set *set, struct sk_buff *skb)
                 goto nla_put_failure;
         NLA_PUT_IPADDR4(skb, IPSET_ATTR_IP, htonl(map->first_ip));
         NLA_PUT_IPADDR4(skb, IPSET_ATTR_IP_TO, htonl(map->last_ip));
-        NLA_PUT_NET32(skb, IPSET_ATTR_REFERENCES,
-                      htonl(atomic_read(&set->ref) - 1));
+        NLA_PUT_NET32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref - 1));
         NLA_PUT_NET32(skb, IPSET_ATTR_MEMSIZE,
                       htonl(sizeof(*map)
                             + (map->last_ip - map->first_ip + 1) * map->dsize));
diff --git a/net/netfilter/ipset/ip_set_bitmap_port.c b/net/netfilter/ipset/ip_set_bitmap_port.c
index 165f09b1a9c..6b38eb8f6ed 100644
--- a/net/netfilter/ipset/ip_set_bitmap_port.c
+++ b/net/netfilter/ipset/ip_set_bitmap_port.c
@@ -320,8 +320,7 @@ bitmap_port_head(struct ip_set *set, struct sk_buff *skb)
                 goto nla_put_failure;
         NLA_PUT_NET16(skb, IPSET_ATTR_PORT, htons(map->first_port));
         NLA_PUT_NET16(skb, IPSET_ATTR_PORT_TO, htons(map->last_port));
-        NLA_PUT_NET32(skb, IPSET_ATTR_REFERENCES,
-                      htonl(atomic_read(&set->ref) - 1));
+        NLA_PUT_NET32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref - 1));
         NLA_PUT_NET32(skb, IPSET_ATTR_MEMSIZE,
                       htonl(sizeof(*map) + map->memsize));
         if (with_timeout(map->timeout))
diff --git a/net/netfilter/ipset/ip_set_core.c b/net/netfilter/ipset/ip_set_core.c
index d6b48230a54..e88ac3c3ed0 100644
--- a/net/netfilter/ipset/ip_set_core.c
+++ b/net/netfilter/ipset/ip_set_core.c
@@ -26,6 +26,7 @@
 
 static LIST_HEAD(ip_set_type_list);             /* all registered set types */
 static DEFINE_MUTEX(ip_set_type_mutex);         /* protects ip_set_type_list */
+static DEFINE_RWLOCK(ip_set_ref_lock);          /* protects the set refs */
 
 static struct ip_set **ip_set_list;             /* all individual sets */
 static ip_set_id_t ip_set_max = CONFIG_IP_SET_MAX; /* max number of sets */
@@ -301,13 +302,18 @@ EXPORT_SYMBOL_GPL(ip_set_get_ipaddr6);
 static inline void
 __ip_set_get(ip_set_id_t index)
 {
-        atomic_inc(&ip_set_list[index]->ref);
+        write_lock_bh(&ip_set_ref_lock);
+        ip_set_list[index]->ref++;
+        write_unlock_bh(&ip_set_ref_lock);
 }
 
 static inline void
 __ip_set_put(ip_set_id_t index)
 {
-        atomic_dec(&ip_set_list[index]->ref);
+        write_lock_bh(&ip_set_ref_lock);
+        BUG_ON(ip_set_list[index]->ref == 0);
+        ip_set_list[index]->ref--;
+        write_unlock_bh(&ip_set_ref_lock);
 }
 
 /*
@@ -324,7 +330,7 @@ ip_set_test(ip_set_id_t index, const struct sk_buff *skb,
         struct ip_set *set = ip_set_list[index];
         int ret = 0;
 
-        BUG_ON(set == NULL || atomic_read(&set->ref) == 0);
+        BUG_ON(set == NULL);
         pr_debug("set %s, index %u\n", set->name, index);
 
         if (dim < set->type->dimension ||
@@ -356,7 +362,7 @@ ip_set_add(ip_set_id_t index, const struct sk_buff *skb,
         struct ip_set *set = ip_set_list[index];
         int ret;
 
-        BUG_ON(set == NULL || atomic_read(&set->ref) == 0);
+        BUG_ON(set == NULL);
         pr_debug("set %s, index %u\n", set->name, index);
 
         if (dim < set->type->dimension ||
@@ -378,7 +384,7 @@ ip_set_del(ip_set_id_t index, const struct sk_buff *skb,
         struct ip_set *set = ip_set_list[index];
         int ret = 0;
 
-        BUG_ON(set == NULL || atomic_read(&set->ref) == 0);
+        BUG_ON(set == NULL);
         pr_debug("set %s, index %u\n", set->name, index);
 
         if (dim < set->type->dimension ||
@@ -397,7 +403,6 @@ EXPORT_SYMBOL_GPL(ip_set_del);
  * Find set by name, reference it once. The reference makes sure the
  * thing pointed to, does not go away under our feet.
  *
- * The nfnl mutex must already be activated.
  */
 ip_set_id_t
 ip_set_get_byname(const char *name, struct ip_set **set)
@@ -423,15 +428,12 @@ EXPORT_SYMBOL_GPL(ip_set_get_byname);
  * reference count by 1. The caller shall not assume the index
  * to be valid, after calling this function.
  *
- * The nfnl mutex must already be activated.
  */
 void
 ip_set_put_byindex(ip_set_id_t index)
 {
-        if (ip_set_list[index] != NULL) {
-                BUG_ON(atomic_read(&ip_set_list[index]->ref) == 0);
+        if (ip_set_list[index] != NULL)
                 __ip_set_put(index);
-        }
 }
 EXPORT_SYMBOL_GPL(ip_set_put_byindex);
 
@@ -441,7 +443,6 @@ EXPORT_SYMBOL_GPL(ip_set_put_byindex);
  * can't be destroyed. The set cannot be renamed due to
  * the referencing either.
  *
- * The nfnl mutex must already be activated.
  */
 const char *
 ip_set_name_byindex(ip_set_id_t index)
@@ -449,7 +450,7 @@ ip_set_name_byindex(ip_set_id_t index)
         const struct ip_set *set = ip_set_list[index];
 
         BUG_ON(set == NULL);
-        BUG_ON(atomic_read(&set->ref) == 0);
+        BUG_ON(set->ref == 0);
 
         /* Referenced, so it's safe */
         return set->name;
@@ -515,10 +516,7 @@ void
 ip_set_nfnl_put(ip_set_id_t index)
 {
         nfnl_lock();
-        if (ip_set_list[index] != NULL) {
-                BUG_ON(atomic_read(&ip_set_list[index]->ref) == 0);
-                __ip_set_put(index);
-        }
+        ip_set_put_byindex(index);
         nfnl_unlock();
 }
 EXPORT_SYMBOL_GPL(ip_set_nfnl_put);
@@ -526,7 +524,7 @@ EXPORT_SYMBOL_GPL(ip_set_nfnl_put);
 /*
  * Communication protocol with userspace over netlink.
  *
- * We already locked by nfnl_lock.
+ * The commands are serialized by the nfnl mutex.
  */
 
 static inline bool
@@ -657,7 +655,6 @@ ip_set_create(struct sock *ctnl, struct sk_buff *skb,
                 return -ENOMEM;
         rwlock_init(&set->lock);
         strlcpy(set->name, name, IPSET_MAXNAMELEN);
-        atomic_set(&set->ref, 0);
         set->family = family;
 
         /*
@@ -690,8 +687,8 @@ ip_set_create(struct sock *ctnl, struct sk_buff *skb,
 
         /*
          * Here, we have a valid, constructed set and we are protected
-         * by nfnl_lock. Find the first free index in ip_set_list and
-         * check clashing.
+         * by the nfnl mutex. Find the first free index in ip_set_list
+         * and check clashing.
          */
         if ((ret = find_free_id(set->name, &index, &clash)) != 0) {
                 /* If this is the same set and requested, ignore error */
@@ -751,31 +748,51 @@ ip_set_destroy(struct sock *ctnl, struct sk_buff *skb,
                const struct nlattr * const attr[])
 {
         ip_set_id_t i;
+        int ret = 0;
 
         if (unlikely(protocol_failed(attr)))
                 return -IPSET_ERR_PROTOCOL;
 
-        /* References are protected by the nfnl mutex */
+        /* Commands are serialized and references are
+         * protected by the ip_set_ref_lock.
+         * External systems (i.e. xt_set) must call
+         * ip_set_put|get_nfnl_* functions, that way we
+         * can safely check references here.
+         *
+         * list:set timer can only decrement the reference
+         * counter, so if it's already zero, we can proceed
+         * without holding the lock.
+         */
+        read_lock_bh(&ip_set_ref_lock);
         if (!attr[IPSET_ATTR_SETNAME]) {
                 for (i = 0; i < ip_set_max; i++) {
-                        if (ip_set_list[i] != NULL &&
-                            (atomic_read(&ip_set_list[i]->ref)))
-                                return -IPSET_ERR_BUSY;
+                        if (ip_set_list[i] != NULL && ip_set_list[i]->ref) {
+                                ret = IPSET_ERR_BUSY;
+                                goto out;
+                        }
                 }
+                read_unlock_bh(&ip_set_ref_lock);
                 for (i = 0; i < ip_set_max; i++) {
                         if (ip_set_list[i] != NULL)
                                 ip_set_destroy_set(i);
                 }
         } else {
                 i = find_set_id(nla_data(attr[IPSET_ATTR_SETNAME]));
-                if (i == IPSET_INVALID_ID)
-                        return -ENOENT;
-                else if (atomic_read(&ip_set_list[i]->ref))
-                        return -IPSET_ERR_BUSY;
+                if (i == IPSET_INVALID_ID) {
+                        ret = -ENOENT;
+                        goto out;
+                } else if (ip_set_list[i]->ref) {
+                        ret = -IPSET_ERR_BUSY;
+                        goto out;
+                }
+                read_unlock_bh(&ip_set_ref_lock);
 
                 ip_set_destroy_set(i);
         }
         return 0;
+out:
+        read_unlock_bh(&ip_set_ref_lock);
+        return ret;
 }
 
 /* Flush sets */
@@ -834,6 +851,7 @@ ip_set_rename(struct sock *ctnl, struct sk_buff *skb,
         struct ip_set *set;
         const char *name2;
         ip_set_id_t i;
+        int ret = 0;
 
         if (unlikely(protocol_failed(attr) ||
                      attr[IPSET_ATTR_SETNAME] == NULL ||
@@ -843,25 +861,33 @@ ip_set_rename(struct sock *ctnl, struct sk_buff *skb,
         set = find_set(nla_data(attr[IPSET_ATTR_SETNAME]));
         if (set == NULL)
                 return -ENOENT;
-        if (atomic_read(&set->ref) != 0)
-                return -IPSET_ERR_REFERENCED;
+
+        read_lock_bh(&ip_set_ref_lock);
+        if (set->ref != 0) {
+                ret = -IPSET_ERR_REFERENCED;
+                goto out;
+        }
 
         name2 = nla_data(attr[IPSET_ATTR_SETNAME2]);
         for (i = 0; i < ip_set_max; i++) {
                 if (ip_set_list[i] != NULL &&
-                    STREQ(ip_set_list[i]->name, name2))
-                        return -IPSET_ERR_EXIST_SETNAME2;
+                    STREQ(ip_set_list[i]->name, name2)) {
+                        ret = -IPSET_ERR_EXIST_SETNAME2;
+                        goto out;
+                }
         }
         strncpy(set->name, name2, IPSET_MAXNAMELEN);
 
-        return 0;
+out:
+        read_unlock_bh(&ip_set_ref_lock);
+        return ret;
 }
 
 /* Swap two sets so that name/index points to the other.
  * References and set names are also swapped.
  *
- * We are protected by the nfnl mutex and references are
- * manipulated only by holding the mutex. The kernel interfaces
+ * The commands are serialized by the nfnl mutex and references are
+ * protected by the ip_set_ref_lock. The kernel interfaces
  * do not hold the mutex but the pointer settings are atomic
  * so the ip_set_list always contains valid pointers to the sets.
  */
@@ -874,7 +900,6 @@ ip_set_swap(struct sock *ctnl, struct sk_buff *skb,
         struct ip_set *from, *to;
         ip_set_id_t from_id, to_id;
         char from_name[IPSET_MAXNAMELEN];
-        u32 from_ref;
 
         if (unlikely(protocol_failed(attr) ||
                      attr[IPSET_ATTR_SETNAME] == NULL ||
@@ -899,17 +924,15 @@ ip_set_swap(struct sock *ctnl, struct sk_buff *skb,
               from->type->family == to->type->family))
                 return -IPSET_ERR_TYPE_MISMATCH;
 
-        /* No magic here: ref munging protected by the nfnl_lock */
         strncpy(from_name, from->name, IPSET_MAXNAMELEN);
-        from_ref = atomic_read(&from->ref);
-
         strncpy(from->name, to->name, IPSET_MAXNAMELEN);
-        atomic_set(&from->ref, atomic_read(&to->ref));
         strncpy(to->name, from_name, IPSET_MAXNAMELEN);
-        atomic_set(&to->ref, from_ref);
 
+        write_lock_bh(&ip_set_ref_lock);
+        swap(from->ref, to->ref);
         ip_set_list[from_id] = to;
         ip_set_list[to_id] = from;
+        write_unlock_bh(&ip_set_ref_lock);
 
         return 0;
 }
@@ -926,7 +949,7 @@ ip_set_dump_done(struct netlink_callback *cb)
 {
         if (cb->args[2]) {
                 pr_debug("release set %s\n", ip_set_list[cb->args[1]]->name);
-                __ip_set_put((ip_set_id_t) cb->args[1]);
+                ip_set_put_byindex((ip_set_id_t) cb->args[1]);
         }
         return 0;
 }
@@ -1068,7 +1091,7 @@ release_refcount:
         /* If there was an error or set is done, release set */
         if (ret || !cb->args[2]) {
                 pr_debug("release set %s\n", ip_set_list[index]->name);
-                __ip_set_put(index);
+                ip_set_put_byindex(index);
         }
 
         /* If we dump all sets, continue with dumping last ones */
diff --git a/net/netfilter/ipset/ip_set_list_set.c b/net/netfilter/ipset/ip_set_list_set.c
index f4a46c0d25f..e9159e99fc4 100644
--- a/net/netfilter/ipset/ip_set_list_set.c
+++ b/net/netfilter/ipset/ip_set_list_set.c
@@ -366,8 +366,7 @@ list_set_head(struct ip_set *set, struct sk_buff *skb)
         NLA_PUT_NET32(skb, IPSET_ATTR_SIZE, htonl(map->size));
         if (with_timeout(map->timeout))
                 NLA_PUT_NET32(skb, IPSET_ATTR_TIMEOUT, htonl(map->timeout));
-        NLA_PUT_NET32(skb, IPSET_ATTR_REFERENCES,
-                      htonl(atomic_read(&set->ref) - 1));
+        NLA_PUT_NET32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref - 1));
         NLA_PUT_NET32(skb, IPSET_ATTR_MEMSIZE,
                       htonl(sizeof(*map) + map->size * map->dsize));
         ipset_nest_end(skb, nested);
@@ -457,8 +456,7 @@ list_set_gc(unsigned long ul_set)
         struct list_set *map = set->data;
         struct set_telem *e;
         u32 i;
-        
-        /* nfnl_lock should be called */
+
         write_lock_bh(&set->lock);
         for (i = 0; i < map->size; i++) {
                 e = list_set_telem(map, i);