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;
}