The kobject_put is only removing the sysfs entry and corresponding entries when its reference counter becomes zero. This tends to lead to collisions when a device is moved between two different network namespaces because some of the sysfs files have to be removed first and then added again to the already moved sysfs entry.
WARNING: CPU: 0 PID: 290 at lib/kobject.c:240 kobject_add_internal+0x5ec/0x8a0 kobject_add_internal failed for batman_adv with -EEXIST, don't try to register things with the same name in the same directory.
But the caller of kobject_put can already remove the sysfs entry before it does the kobject_put. This removal is done even when the reference counter is not yet zero and thus avoids the problem.
Signed-off-by: Sven Eckelmann sven@narfation.org --- v4: - rebase on top of current master - avoid deletes of vlan->kobj when it is a pointer to bat_priv->mesh_obj (happens for untagged vlan and can cause some kernfs warnings) v3: - rebased on top of current master to fix conflicts with newest patches v2: - rebased on top of current master to fix conflicts with newest patches --- net/batman-adv/sysfs.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/net/batman-adv/sysfs.c b/net/batman-adv/sysfs.c index 8528959..4e06cb7 100644 --- a/net/batman-adv/sysfs.c +++ b/net/batman-adv/sysfs.c @@ -713,6 +713,8 @@ rem_attr: for (bat_attr = batadv_mesh_attrs; *bat_attr; ++bat_attr) sysfs_remove_file(bat_priv->mesh_obj, &((*bat_attr)->attr));
+ kobject_uevent(bat_priv->mesh_obj, KOBJ_REMOVE); + kobject_del(bat_priv->mesh_obj); kobject_put(bat_priv->mesh_obj); bat_priv->mesh_obj = NULL; out: @@ -727,6 +729,8 @@ void batadv_sysfs_del_meshif(struct net_device *dev) for (bat_attr = batadv_mesh_attrs; *bat_attr; ++bat_attr) sysfs_remove_file(bat_priv->mesh_obj, &((*bat_attr)->attr));
+ kobject_uevent(bat_priv->mesh_obj, KOBJ_REMOVE); + kobject_del(bat_priv->mesh_obj); kobject_put(bat_priv->mesh_obj); bat_priv->mesh_obj = NULL; } @@ -782,6 +786,10 @@ rem_attr: for (bat_attr = batadv_vlan_attrs; *bat_attr; ++bat_attr) sysfs_remove_file(vlan->kobj, &((*bat_attr)->attr));
+ if (vlan->kobj != bat_priv->mesh_obj) { + kobject_uevent(vlan->kobj, KOBJ_REMOVE); + kobject_del(vlan->kobj); + } kobject_put(vlan->kobj); vlan->kobj = NULL; out: @@ -801,6 +809,10 @@ void batadv_sysfs_del_vlan(struct batadv_priv *bat_priv, for (bat_attr = batadv_vlan_attrs; *bat_attr; ++bat_attr) sysfs_remove_file(vlan->kobj, &((*bat_attr)->attr));
+ if (vlan->kobj != bat_priv->mesh_obj) { + kobject_uevent(vlan->kobj, KOBJ_REMOVE); + kobject_del(vlan->kobj); + } kobject_put(vlan->kobj); vlan->kobj = NULL; } @@ -1103,6 +1115,8 @@ out:
void batadv_sysfs_del_hardif(struct kobject **hardif_obj) { + kobject_uevent(*hardif_obj, KOBJ_REMOVE); + kobject_del(*hardif_obj); kobject_put(*hardif_obj); *hardif_obj = NULL; }