From: Sven Eckelmann sven@narfation.org

hardif_list_lock is unneccessary because we already ensure that no multiple admin operations can take place through rtnl_lock. hardif_list_lock only adds additional overhead and complexity.

Critical functions now check whether they are called with rtnl_lock using ASSERT_RTNL.

It indirectly fixes the problem that orig_hash_del_if() expects that only one interface is deleted from hardif_list at a time, but hardif_remove_interfaces() removes all at once and then calls orig_hash_del_if().

Reported-by: Linus Lüssing linus.luessing@web.de Signed-off-by: Sven Eckelmann sven@narfation.org --- * Also doing the register_netdev->register_netdevice change one commit earlier, as patch 1/2 would otherwise deadlock due to the rtnl_lock() already being grabbed before the hardif_enable_interface() and register_netdev() trying to get it again.

bat_sysfs.c | 2 ++ hard-interface.c | 30 +++++++----------------------- main.c | 3 +++ soft-interface.c | 2 +- 4 files changed, 13 insertions(+), 24 deletions(-)

diff --git a/bat_sysfs.c b/bat_sysfs.c index e449bf6..85ba20d 100644 --- a/bat_sysfs.c +++ b/bat_sysfs.c @@ -502,7 +502,9 @@ static ssize_t store_mesh_iface(struct kobject *kobj, struct attribute *attr, rtnl_unlock(); }

+ rtnl_lock(); ret = hardif_enable_interface(hard_iface, buff); + rtnl_unlock();

out: hardif_free_ref(hard_iface); diff --git a/hard-interface.c b/hard-interface.c index 3e888f1..7e2f772 100644 --- a/hard-interface.c +++ b/hard-interface.c @@ -31,9 +31,6 @@

#include <linux/if_arp.h>

-/* protect update critical side of hardif_list - but not the content */ -static DEFINE_SPINLOCK(hardif_list_lock); -

static int batman_skb_recv(struct sk_buff *skb, struct net_device *dev, @@ -136,7 +133,7 @@ static void primary_if_select(struct bat_priv *bat_priv, struct hard_iface *curr_hard_iface; struct batman_packet *batman_packet;

- spin_lock_bh(&hardif_list_lock); + ASSERT_RTNL();

if (new_hard_iface && !atomic_inc_not_zero(&new_hard_iface->refcount)) new_hard_iface = NULL; @@ -148,7 +145,7 @@ static void primary_if_select(struct bat_priv *bat_priv, hardif_free_ref(curr_hard_iface);

if (!new_hard_iface) - goto out; + return;

batman_packet = (struct batman_packet *)(new_hard_iface->packet_buff); batman_packet->flags = PRIMARIES_FIRST_HOP; @@ -161,9 +158,6 @@ static void primary_if_select(struct bat_priv *bat_priv, * our new primary interface */ atomic_set(&bat_priv->hna_local_changed, 1); - -out: - spin_unlock_bh(&hardif_list_lock); }

static bool hardif_is_iface_up(struct hard_iface *hard_iface) @@ -456,6 +450,8 @@ static struct hard_iface *hardif_add_interface(struct net_device *net_dev) struct hard_iface *hard_iface; int ret;

+ ASSERT_RTNL(); + ret = is_valid_iface(net_dev); if (ret != 1) goto out; @@ -482,10 +478,7 @@ static struct hard_iface *hardif_add_interface(struct net_device *net_dev) atomic_set(&hard_iface->refcount, 2);

check_known_mac_addr(hard_iface->net_dev); - - spin_lock(&hardif_list_lock); list_add_tail_rcu(&hard_iface->list, &hardif_list); - spin_unlock(&hardif_list_lock);

return hard_iface;

@@ -499,6 +492,8 @@ out:

static void hardif_remove_interface(struct hard_iface *hard_iface) { + ASSERT_RTNL(); + /* first deactivate interface */ if (hard_iface->if_status != IF_NOT_IN_USE) hardif_disable_interface(hard_iface); @@ -514,20 +509,11 @@ static void hardif_remove_interface(struct hard_iface *hard_iface) void hardif_remove_interfaces(void) { struct hard_iface *hard_iface, *hard_iface_tmp; - struct list_head if_queue; - - INIT_LIST_HEAD(&if_queue);

- spin_lock(&hardif_list_lock); + rtnl_lock(); list_for_each_entry_safe(hard_iface, hard_iface_tmp, &hardif_list, list) { list_del_rcu(&hard_iface->list); - list_add_tail(&hard_iface->list, &if_queue); - } - spin_unlock(&hardif_list_lock); - - rtnl_lock(); - list_for_each_entry_safe(hard_iface, hard_iface_tmp, &if_queue, list) { hardif_remove_interface(hard_iface); } rtnl_unlock(); @@ -556,9 +542,7 @@ static int hard_if_event(struct notifier_block *this, hardif_deactivate_interface(hard_iface); break; case NETDEV_UNREGISTER: - spin_lock(&hardif_list_lock); list_del_rcu(&hard_iface->list); - spin_unlock(&hardif_list_lock);

hardif_remove_interface(hard_iface); break; diff --git a/main.c b/main.c index 709b33b..39feb5a 100644 --- a/main.c +++ b/main.c @@ -33,6 +33,9 @@ #include "vis.h" #include "hash.h"

+ +/* List manipulations on hardif_list have to be rtnl_lock()'ed, + * list traversals just rcu-locked */ struct list_head hardif_list;

unsigned char broadcast_addr[] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff}; diff --git a/soft-interface.c b/soft-interface.c index 1772e2b..a78e923 100644 --- a/soft-interface.c +++ b/soft-interface.c @@ -639,7 +639,7 @@ struct net_device *softif_create(char *name) goto out; }

- ret = register_netdev(soft_iface); + ret = register_netdevice(soft_iface); if (ret < 0) { pr_err("Unable to register the batman interface '%s': %i\n", name, ret);

From: Sven Eckelmann sven@narfation.org

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 --- bat_sysfs.c | 18 +++++++++--------- 1 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/bat_sysfs.c b/bat_sysfs.c index 85ba20d..497a070 100644 --- a/bat_sysfs.c +++ b/bat_sysfs.c @@ -488,24 +488,24 @@ static ssize_t store_mesh_iface(struct kobject *kobj, struct attribute *attr, (strncmp(hard_iface->soft_iface->name, buff, IFNAMSIZ) == 0)) goto out;

+ if (!rtnl_trylock()) { + ret = -ERESTARTSYS; + goto out; + } + if (status_tmp == IF_NOT_IN_USE) { - rtnl_lock(); hardif_disable_interface(hard_iface); - rtnl_unlock(); - goto out; + goto unlock; }

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

- rtnl_lock(); ret = hardif_enable_interface(hard_iface, buff); - rtnl_unlock();

+unlock: + rtnl_unlock(); out: hardif_free_ref(hard_iface); return ret;