On Tuesday, June 16, 2015 17:10:26 Linus Lüssing wrote:
> So far the mcast tvlv handler did not anticipate the processing of
> multiple incoming OGMs from the same originator at the same time. This
> can lead to various issues:
>
> * Broken refcounting: For instance two mcast handlers might both assume
> that an originator just got multicast capabilities and will together
> wrongly decrease mcast.num_disabled by two, potentially leading to
> an integer underflow.
>
> * Potential kernel panic on hlist_del_rcu(): Two mcast handlers might
> one after another try to do an
> hlist_del_rcu(&orig->mcast_want_all_*_node). The second one will
> cause memory corruption / crashes.
> (Reported by: Sven Eckelmann <sven@narfation.org>)
>
> Right in the beginning the code path makes assumptions about the current
> multicast related state of an originator and bases all updates on that. The
> easiest and least error prune way to fix the issues in this case is to
> serialize multiple mcast handler invocations with a spinlock.
>
> Fixes: 77ec494490d6 ("batman-adv: Announce new capability via multicast
> TVLV") Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
> ---
> multicast.c | 62
> ++++++++++++++++++++++++++++++++++++++++++++++------------ originator.c
> | 4 ++++
> types.h | 3 +++
> 3 files changed, 56 insertions(+), 13 deletions(-)
Applied in revision 7f220ed.
Thanks,
Marek
@@ -565,19 +565,26 @@ batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
*
* If the BATADV_MCAST_WANT_ALL_UNSNOOPABLES flag of this originator,
* orig, has toggled then this method updates counter and list accordingly.
+ *
+ * Caller needs to hold orig->mcast_handler_lock.
*/
static void batadv_mcast_want_unsnoop_update(struct batadv_priv *bat_priv,
struct batadv_orig_node *orig,
uint8_t mcast_flags)
{
+ struct hlist_node *node = &orig->mcast_want_all_unsnoopables_node;
+ struct hlist_head *head = &bat_priv->mcast.want_all_unsnoopables_list;
+
/* switched from flag unset to set */
if (mcast_flags & BATADV_MCAST_WANT_ALL_UNSNOOPABLES &&
!(orig->mcast_flags & BATADV_MCAST_WANT_ALL_UNSNOOPABLES)) {
atomic_inc(&bat_priv->mcast.num_want_all_unsnoopables);
spin_lock_bh(&bat_priv->mcast.want_lists_lock);
- hlist_add_head_rcu(&orig->mcast_want_all_unsnoopables_node,
- &bat_priv->mcast.want_all_unsnoopables_list);
+ /* flag checks above + mcast_handler_lock prevents this */
+ BUG_ON(!hlist_unhashed(node));
+
+ hlist_add_head_rcu(node, head);
spin_unlock_bh(&bat_priv->mcast.want_lists_lock);
/* switched from flag set to unset */
} else if (!(mcast_flags & BATADV_MCAST_WANT_ALL_UNSNOOPABLES) &&
@@ -585,7 +592,10 @@ static void batadv_mcast_want_unsnoop_update(struct batadv_priv *bat_priv,
atomic_dec(&bat_priv->mcast.num_want_all_unsnoopables);
spin_lock_bh(&bat_priv->mcast.want_lists_lock);
- hlist_del_rcu(&orig->mcast_want_all_unsnoopables_node);
+ /* flag checks above + mcast_handler_lock prevents this */
+ BUG_ON(hlist_unhashed(node));
+
+ hlist_del_init_rcu(node);
spin_unlock_bh(&bat_priv->mcast.want_lists_lock);
}
}
@@ -598,19 +608,26 @@ static void batadv_mcast_want_unsnoop_update(struct batadv_priv *bat_priv,
*
* If the BATADV_MCAST_WANT_ALL_IPV4 flag of this originator, orig, has
* toggled then this method updates counter and list accordingly.
+ *
+ * Caller needs to hold orig->mcast_handler_lock.
*/
static void batadv_mcast_want_ipv4_update(struct batadv_priv *bat_priv,
struct batadv_orig_node *orig,
uint8_t mcast_flags)
{
+ struct hlist_node *node = &orig->mcast_want_all_ipv4_node;
+ struct hlist_head *head = &bat_priv->mcast.want_all_ipv4_list;
+
/* switched from flag unset to set */
if (mcast_flags & BATADV_MCAST_WANT_ALL_IPV4 &&
!(orig->mcast_flags & BATADV_MCAST_WANT_ALL_IPV4)) {
atomic_inc(&bat_priv->mcast.num_want_all_ipv4);
spin_lock_bh(&bat_priv->mcast.want_lists_lock);
- hlist_add_head_rcu(&orig->mcast_want_all_ipv4_node,
- &bat_priv->mcast.want_all_ipv4_list);
+ /* flag checks above + mcast_handler_lock prevents this */
+ BUG_ON(!hlist_unhashed(node));
+
+ hlist_add_head_rcu(node, head);
spin_unlock_bh(&bat_priv->mcast.want_lists_lock);
/* switched from flag set to unset */
} else if (!(mcast_flags & BATADV_MCAST_WANT_ALL_IPV4) &&
@@ -618,7 +635,10 @@ static void batadv_mcast_want_ipv4_update(struct batadv_priv *bat_priv,
atomic_dec(&bat_priv->mcast.num_want_all_ipv4);
spin_lock_bh(&bat_priv->mcast.want_lists_lock);
- hlist_del_rcu(&orig->mcast_want_all_ipv4_node);
+ /* flag checks above + mcast_handler_lock prevents this */
+ BUG_ON(hlist_unhashed(node));
+
+ hlist_del_init_rcu(node);
spin_unlock_bh(&bat_priv->mcast.want_lists_lock);
}
}
@@ -631,19 +651,26 @@ static void batadv_mcast_want_ipv4_update(struct batadv_priv *bat_priv,
*
* If the BATADV_MCAST_WANT_ALL_IPV6 flag of this originator, orig, has
* toggled then this method updates counter and list accordingly.
+ *
+ * Caller needs to hold orig->mcast_handler_lock.
*/
static void batadv_mcast_want_ipv6_update(struct batadv_priv *bat_priv,
struct batadv_orig_node *orig,
uint8_t mcast_flags)
{
+ struct hlist_node *node = &orig->mcast_want_all_ipv6_node;
+ struct hlist_head *head = &bat_priv->mcast.want_all_ipv6_list;
+
/* switched from flag unset to set */
if (mcast_flags & BATADV_MCAST_WANT_ALL_IPV6 &&
!(orig->mcast_flags & BATADV_MCAST_WANT_ALL_IPV6)) {
atomic_inc(&bat_priv->mcast.num_want_all_ipv6);
spin_lock_bh(&bat_priv->mcast.want_lists_lock);
- hlist_add_head_rcu(&orig->mcast_want_all_ipv6_node,
- &bat_priv->mcast.want_all_ipv6_list);
+ /* flag checks above + mcast_handler_lock prevents this */
+ BUG_ON(!hlist_unhashed(node));
+
+ hlist_add_head_rcu(node, head);
spin_unlock_bh(&bat_priv->mcast.want_lists_lock);
/* switched from flag set to unset */
} else if (!(mcast_flags & BATADV_MCAST_WANT_ALL_IPV6) &&
@@ -651,7 +678,10 @@ static void batadv_mcast_want_ipv6_update(struct batadv_priv *bat_priv,
atomic_dec(&bat_priv->mcast.num_want_all_ipv6);
spin_lock_bh(&bat_priv->mcast.want_lists_lock);
- hlist_del_rcu(&orig->mcast_want_all_ipv6_node);
+ /* flag checks above + mcast_handler_lock prevents this */
+ BUG_ON(hlist_unhashed(node));
+
+ hlist_del_init_rcu(node);
spin_unlock_bh(&bat_priv->mcast.want_lists_lock);
}
}
@@ -674,6 +704,11 @@ static void batadv_mcast_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
uint8_t mcast_flags = BATADV_NO_FLAGS;
bool orig_initialized;
+ if (orig_mcast_enabled && tvlv_value &&
+ (tvlv_value_len >= sizeof(mcast_flags)))
+ mcast_flags = *(uint8_t *)tvlv_value;
+
+ spin_lock_bh(&orig->mcast_handler_lock);
orig_initialized = orig->capa_initialized & BATADV_ORIG_CAPA_HAS_MCAST;
/* If mcast support is turned on decrease the disabled mcast node
@@ -698,15 +733,12 @@ static void batadv_mcast_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
set_bit(BATADV_ORIG_CAPA_HAS_MCAST, &orig->capa_initialized);
- if (orig_mcast_enabled && tvlv_value &&
- (tvlv_value_len >= sizeof(mcast_flags)))
- mcast_flags = *(uint8_t *)tvlv_value;
-
batadv_mcast_want_unsnoop_update(bat_priv, orig, mcast_flags);
batadv_mcast_want_ipv4_update(bat_priv, orig, mcast_flags);
batadv_mcast_want_ipv6_update(bat_priv, orig, mcast_flags);
orig->mcast_flags = mcast_flags;
+ spin_unlock_bh(&orig->mcast_handler_lock);
}
/**
@@ -740,6 +772,8 @@ void batadv_mcast_purge_orig(struct batadv_orig_node *orig)
{
struct batadv_priv *bat_priv = orig->bat_priv;
+ spin_lock_bh(&orig->mcast_handler_lock);
+
if (!(orig->capabilities & BATADV_ORIG_CAPA_HAS_MCAST) &&
orig->capa_initialized & BATADV_ORIG_CAPA_HAS_MCAST)
atomic_dec(&bat_priv->mcast.num_disabled);
@@ -747,4 +781,6 @@ void batadv_mcast_purge_orig(struct batadv_orig_node *orig)
batadv_mcast_want_unsnoop_update(bat_priv, orig, BATADV_NO_FLAGS);
batadv_mcast_want_ipv4_update(bat_priv, orig, BATADV_NO_FLAGS);
batadv_mcast_want_ipv6_update(bat_priv, orig, BATADV_NO_FLAGS);
+
+ spin_unlock_bh(&orig->mcast_handler_lock);
}
@@ -658,11 +658,15 @@ struct batadv_orig_node *batadv_orig_node_new(struct batadv_priv *bat_priv,
INIT_HLIST_HEAD(&orig_node->neigh_list);
INIT_LIST_HEAD(&orig_node->vlan_list);
INIT_HLIST_HEAD(&orig_node->ifinfo_list);
+ INIT_HLIST_NODE(&orig_node->mcast_want_all_unsnoopables_node);
+ INIT_HLIST_NODE(&orig_node->mcast_want_all_ipv4_node);
+ INIT_HLIST_NODE(&orig_node->mcast_want_all_ipv6_node);
spin_lock_init(&orig_node->bcast_seqno_lock);
spin_lock_init(&orig_node->neigh_list_lock);
spin_lock_init(&orig_node->tt_buff_lock);
spin_lock_init(&orig_node->tt_lock);
spin_lock_init(&orig_node->vlan_list_lock);
+ spin_lock_init(&orig_node->mcast_handler_lock);
batadv_nc_init_orig(orig_node);
@@ -204,6 +204,7 @@ struct batadv_orig_bat_iv {
* @batadv_dat_addr_t: address of the orig node in the distributed hash
* @last_seen: time when last packet from this node was received
* @bcast_seqno_reset: time when the broadcast seqno window was reset
+ * @mcast_handler_lock: synchronizes mcast-capability and -flag changes
* @mcast_flags: multicast flags announced by the orig node
* @mcast_want_all_unsnoop_node: a list node for the
* mcast.want_all_unsnoopables list
@@ -251,6 +252,8 @@ struct batadv_orig_node {
unsigned long last_seen;
unsigned long bcast_seqno_reset;
#ifdef CONFIG_BATMAN_ADV_MCAST
+ /* synchronizes mcast tvlv specific orig changes */
+ spinlock_t mcast_handler_lock;
uint8_t mcast_flags;
struct hlist_node mcast_want_all_unsnoopables_node;
struct hlist_node mcast_want_all_ipv4_node;