We currently try to call unregister_netdev when we can destroy a softif after all corresponding hard-interfaces announced that they will be removed.

This will be done when we receive a hard_if_event which already takes the rtnl semaphore and thus we try to get it again in unregister_netdev. This results in a deadlock. This call to unregister_netdev cannot easily replaced by unregister_netdevice, because other parts of the batman-adv module still call that code indirectly without holding the rtnl semaphore.

(needs rtln_unlocked) unregister_netdev ^ | softif_destroy ^ | hardif_disable_interface ^ ^ / | store_mesh_iface hardif_remove_interface (rtln_unlocked) ^ ^ | \ hardif_remove_interfaces hard_if_event ^ (rtln_locked) | batman_exit (rtln_unlocked)

A consistent workaround is to change store_mesh_iface and hardif_remove_interfaces to call rtnl_lock before they call the mentioned child function, release the semaphore afterwards and change unregister_netdev in softif_destroy to unregister_netdevice.

Reported-by: Kazuki Shimada zukky@bb.banban.jp Signed-off-by: Sven Eckelmann sven.eckelmann@gmx.de --- batman-adv/bat_sysfs.c | 7 ++++++- batman-adv/hard-interface.c | 5 ++++- batman-adv/soft-interface.c | 2 +- 3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/batman-adv/bat_sysfs.c b/batman-adv/bat_sysfs.c index 1331a02..8e180ba 100644 --- a/batman-adv/bat_sysfs.c +++ b/batman-adv/bat_sysfs.c @@ -492,13 +492,18 @@ static ssize_t store_mesh_iface(struct kobject *kobj, struct attribute *attr, return count;

if (status_tmp == IF_NOT_IN_USE) { + rtnl_lock(); hardif_disable_interface(batman_if); + rtnl_unlock(); return count; }

/* if the interface already is in use */ - if (batman_if->if_status != IF_NOT_IN_USE) + if (batman_if->if_status != IF_NOT_IN_USE) { + rtnl_lock(); hardif_disable_interface(batman_if); + rtnl_unlock(); + }

return hardif_enable_interface(batman_if, buff); } diff --git a/batman-adv/hard-interface.c b/batman-adv/hard-interface.c index a437ec3..b12f63b 100644 --- a/batman-adv/hard-interface.c +++ b/batman-adv/hard-interface.c @@ -441,8 +441,11 @@ void hardif_remove_interfaces(void) { struct batman_if *batman_if, *batman_if_tmp;

- list_for_each_entry_safe(batman_if, batman_if_tmp, &if_list, list) + list_for_each_entry_safe(batman_if, batman_if_tmp, &if_list, list) { + rtnl_lock(); hardif_remove_interface(batman_if); + rtnl_unlock(); + } }

static int hard_if_event(struct notifier_block *this, diff --git a/batman-adv/soft-interface.c b/batman-adv/soft-interface.c index a45626e..38134ae 100644 --- a/batman-adv/soft-interface.c +++ b/batman-adv/soft-interface.c @@ -351,7 +351,7 @@ void softif_destroy(struct net_device *soft_iface) debugfs_del_meshif(soft_iface); sysfs_del_meshif(soft_iface); mesh_free(soft_iface); - unregister_netdev(soft_iface); + unregister_netdevice(soft_iface); }

/* ethtool */