batman-adv: Avoid deadlock between rtnl_lock and s_active
The hard_if_event is called by the notifier with rtnl_lock and tries to
remove sysfs entries when a NETDEV_UNREGISTER event is received. This
will automatically take the s_active lock.
The s_active lock is also used when a new interface is added to a meshif
through sysfs. In that situation we cannot wait for the rntl_lock before
creating the actual batman-adv interface to prevent a deadlock. It is
still possible to try to get the rtnl_lock and immediately abort the
current operation when the trylock call failed.
Signed-off-by: Sven Eckelmann <sven@narfation.org>
diff --git a/net/batman-adv/bat_sysfs.c b/net/batman-adv/bat_sysfs.c
index 85ba20d..497a070 100644
--- a/net/batman-adv/bat_sysfs.c
+++ b/net/batman-adv/bat_sysfs.c
@@ -488,24 +488,24 @@
(strncmp(hard_iface->soft_iface->name, buff, IFNAMSIZ) == 0))
goto out;
- if (status_tmp == IF_NOT_IN_USE) {
- rtnl_lock();
- hardif_disable_interface(hard_iface);
- rtnl_unlock();
+ if (!rtnl_trylock()) {
+ ret = -ERESTARTSYS;
goto out;
}
- /* if the interface already is in use */
- if (hard_iface->if_status != IF_NOT_IN_USE) {
- rtnl_lock();
+ if (status_tmp == IF_NOT_IN_USE) {
hardif_disable_interface(hard_iface);
- rtnl_unlock();
+ goto unlock;
}
- rtnl_lock();
- ret = hardif_enable_interface(hard_iface, buff);
- rtnl_unlock();
+ /* if the interface already is in use */
+ if (hard_iface->if_status != IF_NOT_IN_USE)
+ hardif_disable_interface(hard_iface);
+ ret = hardif_enable_interface(hard_iface, buff);
+
+unlock:
+ rtnl_unlock();
out:
hardif_free_ref(hard_iface);
return ret;
