batman-adv: Correct rcu refcounting for batman_if
It might be possible that 2 threads access the same data in the same
rcu grace period. The first thread calls call_rcu() to decrement the
refcount and free the data while the second thread increases the
refcount to use the data. To avoid this race condition all refcount
operations have to be atomic.
Reported-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
diff --git a/net/batman-adv/bat_sysfs.c b/net/batman-adv/bat_sysfs.c
index f7b93a0..93ae20a 100644
--- a/net/batman-adv/bat_sysfs.c
+++ b/net/batman-adv/bat_sysfs.c
@@ -450,7 +450,7 @@
length = sprintf(buff, "%s\n", batman_if->if_status == IF_NOT_IN_USE ?
"none" : batman_if->soft_iface->name);
- kref_put(&batman_if->refcount, hardif_free_ref);
+ hardif_free_ref(batman_if);
return length;
}
@@ -461,7 +461,7 @@
struct net_device *net_dev = kobj_to_netdev(kobj);
struct batman_if *batman_if = get_batman_if_by_netdev(net_dev);
int status_tmp = -1;
- int ret;
+ int ret = count;
if (!batman_if)
return count;
@@ -472,7 +472,7 @@
if (strlen(buff) >= IFNAMSIZ) {
pr_err("Invalid parameter for 'mesh_iface' setting received: "
"interface name too long '%s'\n", buff);
- kref_put(&batman_if->refcount, hardif_free_ref);
+ hardif_free_ref(batman_if);
return -EINVAL;
}
@@ -482,17 +482,14 @@
status_tmp = IF_I_WANT_YOU;
if ((batman_if->if_status == status_tmp) || ((batman_if->soft_iface) &&
- (strncmp(batman_if->soft_iface->name, buff, IFNAMSIZ) == 0))) {
- kref_put(&batman_if->refcount, hardif_free_ref);
- return count;
- }
+ (strncmp(batman_if->soft_iface->name, buff, IFNAMSIZ) == 0)))
+ goto out;
if (status_tmp == IF_NOT_IN_USE) {
rtnl_lock();
hardif_disable_interface(batman_if);
rtnl_unlock();
- kref_put(&batman_if->refcount, hardif_free_ref);
- return count;
+ goto out;
}
/* if the interface already is in use */
@@ -503,8 +500,9 @@
}
ret = hardif_enable_interface(batman_if, buff);
- kref_put(&batman_if->refcount, hardif_free_ref);
+out:
+ hardif_free_ref(batman_if);
return ret;
}
@@ -537,7 +535,7 @@
break;
}
- kref_put(&batman_if->refcount, hardif_free_ref);
+ hardif_free_ref(batman_if);
return length;
}
diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index e2b001a..8982485 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -40,13 +40,13 @@
struct packet_type *ptype,
struct net_device *orig_dev);
-static void hardif_free_rcu(struct rcu_head *rcu)
+void hardif_free_rcu(struct rcu_head *rcu)
{
struct batman_if *batman_if;
batman_if = container_of(rcu, struct batman_if, rcu);
dev_put(batman_if->net_dev);
- kref_put(&batman_if->refcount, hardif_free_ref);
+ kfree(batman_if);
}
struct batman_if *get_batman_if_by_netdev(struct net_device *net_dev)
@@ -55,16 +55,14 @@
rcu_read_lock();
list_for_each_entry_rcu(batman_if, &if_list, list) {
- if (batman_if->net_dev == net_dev)
+ if (batman_if->net_dev == net_dev &&
+ atomic_inc_not_zero(&batman_if->refcount))
goto out;
}
batman_if = NULL;
out:
- if (batman_if)
- kref_get(&batman_if->refcount);
-
rcu_read_unlock();
return batman_if;
}
@@ -105,16 +103,14 @@
if (batman_if->soft_iface != soft_iface)
continue;
- if (batman_if->if_status == IF_ACTIVE)
+ if (batman_if->if_status == IF_ACTIVE &&
+ atomic_inc_not_zero(&batman_if->refcount))
goto out;
}
batman_if = NULL;
out:
- if (batman_if)
- kref_get(&batman_if->refcount);
-
rcu_read_unlock();
return batman_if;
}
@@ -137,14 +133,14 @@
struct batman_packet *batman_packet;
struct batman_if *old_if;
- if (batman_if)
- kref_get(&batman_if->refcount);
+ if (batman_if && !atomic_inc_not_zero(&batman_if->refcount))
+ batman_if = NULL;
old_if = bat_priv->primary_if;
bat_priv->primary_if = batman_if;
if (old_if)
- kref_put(&old_if->refcount, hardif_free_ref);
+ hardif_free_ref(old_if);
if (!bat_priv->primary_if)
return;
@@ -290,6 +286,9 @@
if (batman_if->if_status != IF_NOT_IN_USE)
goto out;
+ if (!atomic_inc_not_zero(&batman_if->refcount))
+ goto out;
+
batman_if->soft_iface = dev_get_by_name(&init_net, iface_name);
if (!batman_if->soft_iface) {
@@ -328,7 +327,6 @@
batman_if->batman_adv_ptype.type = __constant_htons(ETH_P_BATMAN);
batman_if->batman_adv_ptype.func = batman_skb_recv;
batman_if->batman_adv_ptype.dev = batman_if->net_dev;
- kref_get(&batman_if->refcount);
dev_add_pack(&batman_if->batman_adv_ptype);
atomic_set(&batman_if->seqno, 1);
@@ -371,6 +369,7 @@
return 0;
err:
+ hardif_free_ref(batman_if);
return -ENOMEM;
}
@@ -387,7 +386,6 @@
bat_info(batman_if->soft_iface, "Removing interface: %s\n",
batman_if->net_dev->name);
dev_remove_pack(&batman_if->batman_adv_ptype);
- kref_put(&batman_if->refcount, hardif_free_ref);
bat_priv->num_ifaces--;
orig_hash_del_if(batman_if, bat_priv->num_ifaces);
@@ -399,7 +397,7 @@
set_primary_if(bat_priv, new_if);
if (new_if)
- kref_put(&new_if->refcount, hardif_free_ref);
+ hardif_free_ref(new_if);
}
kfree(batman_if->packet_buff);
@@ -416,6 +414,7 @@
softif_destroy(batman_if->soft_iface);
batman_if->soft_iface = NULL;
+ hardif_free_ref(batman_if);
}
static struct batman_if *hardif_add_interface(struct net_device *net_dev)
@@ -445,7 +444,8 @@
batman_if->soft_iface = NULL;
batman_if->if_status = IF_NOT_IN_USE;
INIT_LIST_HEAD(&batman_if->list);
- kref_init(&batman_if->refcount);
+ /* extra reference for return */
+ atomic_set(&batman_if->refcount, 2);
check_known_mac_addr(batman_if->net_dev);
@@ -453,8 +453,6 @@
list_add_tail_rcu(&batman_if->list, &if_list);
spin_unlock(&if_list_lock);
- /* extra reference for return */
- kref_get(&batman_if->refcount);
return batman_if;
free_if:
@@ -476,7 +474,7 @@
batman_if->if_status = IF_TO_BE_REMOVED;
sysfs_del_hardif(&batman_if->hardif_obj);
- call_rcu(&batman_if->rcu, hardif_free_rcu);
+ hardif_free_ref(batman_if);
}
void hardif_remove_interfaces(void)
@@ -548,7 +546,7 @@
};
hardif_put:
- kref_put(&batman_if->refcount, hardif_free_ref);
+ hardif_free_ref(batman_if);
out:
return NOTIFY_DONE;
}
diff --git a/net/batman-adv/hard-interface.h b/net/batman-adv/hard-interface.h
index ad19543..e488b90 100644
--- a/net/batman-adv/hard-interface.h
+++ b/net/batman-adv/hard-interface.h
@@ -37,13 +37,12 @@
void hardif_remove_interfaces(void);
int hardif_min_mtu(struct net_device *soft_iface);
void update_min_mtu(struct net_device *soft_iface);
+void hardif_free_rcu(struct rcu_head *rcu);
-static inline void hardif_free_ref(struct kref *refcount)
+static inline void hardif_free_ref(struct batman_if *batman_if)
{
- struct batman_if *batman_if;
-
- batman_if = container_of(refcount, struct batman_if, refcount);
- kfree(batman_if);
+ if (atomic_dec_and_test(&batman_if->refcount))
+ call_rcu(&batman_if->rcu, hardif_free_rcu);
}
#endif /* _NET_BATMAN_ADV_HARD_INTERFACE_H_ */
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 96f7c22..e0140c6 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -43,7 +43,7 @@
unsigned char *packet_buff;
int packet_len;
struct kobject *hardif_obj;
- struct kref refcount;
+ atomic_t refcount;
struct packet_type batman_adv_ptype;
struct net_device *soft_iface;
struct rcu_head rcu;