Repository : ssh://git@open-mesh.org/batman-adv

On branch : master

commit d3be478f1aa27b47f61c4a62e18eb063d47c9168 Author: Sven Eckelmann sven@narfation.org Date: Sun Oct 13 21:03:07 2019 +0200

batman-adv: Avoid OGM workqueue synchronous cancel deadlock

batadv_forw_packet_list_free can be called when an interface is being disabled. Under this circumstance, the rntl_lock will be held and while it calls cancel_delayed_work_sync.

cancel_delayed_work_sync will stop the execution of the current context when the work item is currently processed. It can now happen that the cancel_delayed_work_sync was called when rtnl_lock was already called in batadv_iv_send_outstanding_bat_ogm_packet or when it was in the process of calling it. In this case, batadv_iv_send_outstanding_bat_ogm_packet waits for the lock and cancel_delayed_work_sync (which holds the rtnl_lock) is waiting for batadv_iv_send_outstanding_bat_ogm_packet to finish.

This can only be avoided by not using (conflicting) blocking locks while cancel_delayed_work_sync is called. It also has the benefit that the ogm scheduling functionality can avoid unnecessary delays which can be introduced by a global lock.

Fixes: 9b8ceef26c69 ("batman-adv: Avoid free/alloc race when handling OGM buffer") Signed-off-by: Sven Eckelmann sven@narfation.org

d3be478f1aa27b47f61c4a62e18eb063d47c9168 net/batman-adv/bat_iv_ogm.c | 86 ++++++++++++++++++++++++++--------------- net/batman-adv/hard-interface.c | 2 + net/batman-adv/types.h | 7 +++- 3 files changed, 61 insertions(+), 34 deletions(-)

diff --git a/net/batman-adv/bat_iv_ogm.c b/net/batman-adv/bat_iv_ogm.c index e20c3813..5b0b20e6 100644 --- a/net/batman-adv/bat_iv_ogm.c +++ b/net/batman-adv/bat_iv_ogm.c @@ -22,6 +22,8 @@ #include <linux/kernel.h> #include <linux/kref.h> #include <linux/list.h> +#include <linux/lockdep.h> +#include <linux/mutex.h> #include <linux/netdevice.h> #include <linux/netlink.h> #include <linux/pkt_sched.h> @@ -29,7 +31,6 @@ #include <linux/random.h> #include <linux/rculist.h> #include <linux/rcupdate.h> -#include <linux/rtnetlink.h> #include <linux/seq_file.h> #include <linux/skbuff.h> #include <linux/slab.h> @@ -194,7 +195,7 @@ static int batadv_iv_ogm_iface_enable(struct batadv_hard_iface *hard_iface) unsigned char *ogm_buff; u32 random_seqno;

- ASSERT_RTNL(); + mutex_lock(&hard_iface->bat_iv.ogm_buff_mutex);

/* randomize initial seqno to avoid collision */ get_random_bytes(&random_seqno, sizeof(random_seqno)); @@ -202,8 +203,10 @@ static int batadv_iv_ogm_iface_enable(struct batadv_hard_iface *hard_iface)

hard_iface->bat_iv.ogm_buff_len = BATADV_OGM_HLEN; ogm_buff = kmalloc(hard_iface->bat_iv.ogm_buff_len, GFP_ATOMIC); - if (!ogm_buff) + if (!ogm_buff) { + mutex_unlock(&hard_iface->bat_iv.ogm_buff_mutex); return -ENOMEM; + }

hard_iface->bat_iv.ogm_buff = ogm_buff;

@@ -215,41 +218,59 @@ static int batadv_iv_ogm_iface_enable(struct batadv_hard_iface *hard_iface) batadv_ogm_packet->reserved = 0; batadv_ogm_packet->tq = BATADV_TQ_MAX_VALUE;

+ mutex_unlock(&hard_iface->bat_iv.ogm_buff_mutex); + return 0; }

static void batadv_iv_ogm_iface_disable(struct batadv_hard_iface *hard_iface) { - ASSERT_RTNL(); + mutex_lock(&hard_iface->bat_iv.ogm_buff_mutex);

kfree(hard_iface->bat_iv.ogm_buff); hard_iface->bat_iv.ogm_buff = NULL; + + mutex_unlock(&hard_iface->bat_iv.ogm_buff_mutex); }

static void batadv_iv_ogm_iface_update_mac(struct batadv_hard_iface *hard_iface) { struct batadv_ogm_packet *batadv_ogm_packet; - unsigned char *ogm_buff = hard_iface->bat_iv.ogm_buff; + void *ogm_buff;

- ASSERT_RTNL(); + mutex_lock(&hard_iface->bat_iv.ogm_buff_mutex);

- batadv_ogm_packet = (struct batadv_ogm_packet *)ogm_buff; + ogm_buff = hard_iface->bat_iv.ogm_buff; + if (!ogm_buff) + goto unlock; + + batadv_ogm_packet = ogm_buff; ether_addr_copy(batadv_ogm_packet->orig, hard_iface->net_dev->dev_addr); ether_addr_copy(batadv_ogm_packet->prev_sender, hard_iface->net_dev->dev_addr); + +unlock: + mutex_unlock(&hard_iface->bat_iv.ogm_buff_mutex); }

static void batadv_iv_ogm_primary_iface_set(struct batadv_hard_iface *hard_iface) { struct batadv_ogm_packet *batadv_ogm_packet; - unsigned char *ogm_buff = hard_iface->bat_iv.ogm_buff; + void *ogm_buff;

- ASSERT_RTNL(); + mutex_lock(&hard_iface->bat_iv.ogm_buff_mutex);

- batadv_ogm_packet = (struct batadv_ogm_packet *)ogm_buff; + ogm_buff = hard_iface->bat_iv.ogm_buff; + if (!ogm_buff) + goto unlock; + + batadv_ogm_packet = ogm_buff; batadv_ogm_packet->ttl = BATADV_TTL; + +unlock: + mutex_unlock(&hard_iface->bat_iv.ogm_buff_mutex); }

/* when do we schedule our own ogm to be sent */ @@ -751,7 +772,11 @@ batadv_iv_ogm_slide_own_bcast_window(struct batadv_hard_iface *hard_iface) } }

-static void batadv_iv_ogm_schedule(struct batadv_hard_iface *hard_iface) +/** + * batadv_iv_ogm_schedule_buff() - schedule submission of hardif ogm buffer + * @hard_iface: interface whose ogm buffer should be transmitted + */ +static void batadv_iv_ogm_schedule_buff(struct batadv_hard_iface *hard_iface) { struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface); unsigned char **ogm_buff = &hard_iface->bat_iv.ogm_buff; @@ -762,11 +787,7 @@ static void batadv_iv_ogm_schedule(struct batadv_hard_iface *hard_iface) u16 tvlv_len = 0; unsigned long send_time;

- ASSERT_RTNL(); - - if (hard_iface->if_status == BATADV_IF_NOT_IN_USE || - hard_iface->if_status == BATADV_IF_TO_BE_REMOVED) - return; + lockdep_assert_held(&hard_iface->bat_iv.ogm_buff_mutex);

/* the interface gets activated here to avoid race conditions between * the moment of activating the interface in @@ -834,6 +855,17 @@ out: batadv_hardif_put(primary_if); }

+static void batadv_iv_ogm_schedule(struct batadv_hard_iface *hard_iface) +{ + if (hard_iface->if_status == BATADV_IF_NOT_IN_USE || + hard_iface->if_status == BATADV_IF_TO_BE_REMOVED) + return; + + mutex_lock(&hard_iface->bat_iv.ogm_buff_mutex); + batadv_iv_ogm_schedule_buff(hard_iface); + mutex_unlock(&hard_iface->bat_iv.ogm_buff_mutex); +} + /** * batadv_iv_orig_ifinfo_sum() - Get bcast_own sum for originator over iterface * @orig_node: originator which reproadcasted the OGMs directly @@ -1654,12 +1686,16 @@ static void batadv_iv_ogm_process(const struct sk_buff *skb, int ogm_offset, batadv_orig_node_put(orig_node); }

-static void -batadv_iv_send_outstanding_forw_packet(struct batadv_forw_packet *forw_packet) +static void batadv_iv_send_outstanding_bat_ogm_packet(struct work_struct *work) { + struct delayed_work *delayed_work; + struct batadv_forw_packet *forw_packet; struct batadv_priv *bat_priv; bool dropped = false;

+ delayed_work = to_delayed_work(work); + forw_packet = container_of(delayed_work, struct batadv_forw_packet, + delayed_work); bat_priv = netdev_priv(forw_packet->if_incoming->soft_iface);

if (atomic_read(&bat_priv->mesh_state) == BATADV_MESH_DEACTIVATING) { @@ -1688,20 +1724,6 @@ out: batadv_forw_packet_free(forw_packet, dropped); }

-static void batadv_iv_send_outstanding_bat_ogm_packet(struct work_struct *work) -{ - struct delayed_work *delayed_work; - struct batadv_forw_packet *forw_packet; - - delayed_work = to_delayed_work(work); - forw_packet = container_of(delayed_work, struct batadv_forw_packet, - delayed_work); - - rtnl_lock(); - batadv_iv_send_outstanding_forw_packet(forw_packet); - rtnl_unlock(); -} - static int batadv_iv_ogm_receive(struct sk_buff *skb, struct batadv_hard_iface *if_incoming) { diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c index c90e4734..afb52282 100644 --- a/net/batman-adv/hard-interface.c +++ b/net/batman-adv/hard-interface.c @@ -18,6 +18,7 @@ #include <linux/kref.h> #include <linux/limits.h> #include <linux/list.h> +#include <linux/mutex.h> #include <linux/netdevice.h> #include <linux/printk.h> #include <linux/rculist.h> @@ -929,6 +930,7 @@ batadv_hardif_add_interface(struct net_device *net_dev) INIT_LIST_HEAD(&hard_iface->list); INIT_HLIST_HEAD(&hard_iface->neigh_list);

+ mutex_init(&hard_iface->bat_iv.ogm_buff_mutex); spin_lock_init(&hard_iface->neigh_list_lock); kref_init(&hard_iface->refcount);

diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h index eded9167..aa038b91 100644 --- a/net/batman-adv/types.h +++ b/net/batman-adv/types.h @@ -74,14 +74,17 @@ enum batadv_dhcp_recipient { * struct batadv_hard_iface_bat_iv - per hard-interface B.A.T.M.A.N. IV data */ struct batadv_hard_iface_bat_iv { - /** @ogm_buff: buffer holding the OGM packet. rtnl protected */ + /** @ogm_buff: buffer holding the OGM packet */ unsigned char *ogm_buff;

- /** @ogm_buff_len: length of the OGM packet buffer. rtnl protected */ + /** @ogm_buff_len: length of the OGM packet buffer */ int ogm_buff_len;

/** @ogm_seqno: OGM sequence number - used to identify each OGM */ atomic_t ogm_seqno; + + /** @ogm_buff_mutex: lock protecting ogm_buff and ogm_buff_len */ + struct mutex ogm_buff_mutex; };

/**