A malicious actor behind one bridge port may spam the kernel with OGMs with a random source MAC address, each of which will create a neighbor node entry, each of which is a dynamic allocation in the kernel. This will at some point exhaust the available memory.
Mitigate this by maintaining a per meshif count of those automatically generated entries in neigh_learned, and a limit in neigh_max_learned. If the limit is hit new entries are not learned anymore. For backwards compatibility, the default setting of 0 disables the limit. Signed-off-by: Sven Eckelmann <[email protected]> --- include/uapi/linux/batman_adv.h | 6 ++++++ net/batman-adv/mesh-interface.c | 3 +++ net/batman-adv/netlink.c | 11 +++++++++++ net/batman-adv/originator.c | 12 ++++++++++++ net/batman-adv/types.h | 6 ++++++ 5 files changed, 38 insertions(+) diff --git a/include/uapi/linux/batman_adv.h b/include/uapi/linux/batman_adv.h index 936bcac2..addb6092 100644 --- a/include/uapi/linux/batman_adv.h +++ b/include/uapi/linux/batman_adv.h @@ -481,6 +481,12 @@ enum batadv_nl_attrs { */ BATADV_ATTR_MULTICAST_FANOUT, + /** + * @BATADV_ATTR_NEIGH_MAX_LEARNED: defines the maximum number of neighbors + * which can be learned in parallel + */ + BATADV_ATTR_NEIGH_MAX_LEARNED, + /* add attributes above here, update the policy in netlink.c */ /** diff --git a/net/batman-adv/mesh-interface.c b/net/batman-adv/mesh-interface.c index 50c26037..b9302c58 100644 --- a/net/batman-adv/mesh-interface.c +++ b/net/batman-adv/mesh-interface.c @@ -790,6 +790,9 @@ static int batadv_meshif_init_late(struct net_device *dev) #endif atomic_set(&bat_priv->tp_num, 0); + atomic_set(&bat_priv->neigh_learned, 0); + WRITE_ONCE(bat_priv->neigh_max_learned, 0); + WRITE_ONCE(bat_priv->tt.local_changes, 0); bat_priv->tt.last_changeset = NULL; bat_priv->tt.last_changeset_len = 0; diff --git a/net/batman-adv/netlink.c b/net/batman-adv/netlink.c index e52f44e7..915a7d74 100644 --- a/net/batman-adv/netlink.c +++ b/net/batman-adv/netlink.c @@ -13,6 +13,7 @@ #include <linux/bug.h> #include <linux/byteorder/generic.h> #include <linux/cache.h> +#include <linux/compiler.h> #include <linux/err.h> #include <linux/errno.h> #include <linux/gfp.h> @@ -146,6 +147,7 @@ static const struct nla_policy batadv_netlink_policy[NUM_BATADV_ATTR] = { [BATADV_ATTR_ORIG_INTERVAL] = { .type = NLA_U32 }, [BATADV_ATTR_ELP_INTERVAL] = { .type = NLA_U32 }, [BATADV_ATTR_THROUGHPUT_OVERRIDE] = { .type = NLA_U32 }, + [BATADV_ATTR_NEIGH_MAX_LEARNED] = { .type = NLA_U32 }, }; /** @@ -347,6 +349,10 @@ static int batadv_netlink_mesh_fill(struct sk_buff *msg, atomic_read(&bat_priv->orig_interval))) goto nla_put_failure; + if (nla_put_u32(msg, BATADV_ATTR_NEIGH_MAX_LEARNED, + READ_ONCE(bat_priv->neigh_max_learned))) + goto nla_put_failure; + batadv_hardif_put(primary_if); genlmsg_end(msg, hdr); @@ -592,6 +598,11 @@ static int batadv_netlink_set_mesh(struct sk_buff *skb, struct genl_info *info) atomic_set(&bat_priv->orig_interval, orig_interval); } + if (info->attrs[BATADV_ATTR_NEIGH_MAX_LEARNED]) { + WRITE_ONCE(bat_priv->neigh_max_learned, + nla_get_u32(info->attrs[BATADV_ATTR_NEIGH_MAX_LEARNED])); + } + batadv_netlink_notify_mesh(bat_priv); return 0; diff --git a/net/batman-adv/originator.c b/net/batman-adv/originator.c index b3468cca..90f553fc 100644 --- a/net/batman-adv/originator.c +++ b/net/batman-adv/originator.c @@ -671,6 +671,8 @@ batadv_neigh_node_create(struct batadv_orig_node *orig_node, { struct batadv_neigh_node *neigh_node; struct batadv_hardif_neigh_node *hardif_neigh = NULL; + u32 neigh_max_learned; + int neigh_learned; spin_lock_bh(&orig_node->neigh_list_lock); @@ -678,6 +680,11 @@ batadv_neigh_node_create(struct batadv_orig_node *orig_node, if (neigh_node) goto out; + neigh_max_learned = READ_ONCE(orig_node->bat_priv->neigh_max_learned); + neigh_learned = atomic_read(&orig_node->bat_priv->neigh_learned); + if (neigh_max_learned && neigh_learned >= neigh_max_learned) + goto out; + hardif_neigh = batadv_hardif_neigh_get_or_create(hard_iface, neigh_addr, orig_node); if (!hardif_neigh) @@ -701,6 +708,8 @@ batadv_neigh_node_create(struct batadv_orig_node *orig_node, kref_get(&hardif_neigh->refcount); neigh_node->hardif_neigh = hardif_neigh; + atomic_inc(&orig_node->bat_priv->neigh_learned); + /* extra reference for return */ kref_init(&neigh_node->refcount); @@ -866,6 +875,8 @@ void batadv_orig_node_release(struct kref *ref) &orig_node->neigh_list, list) { hlist_del_rcu(&neigh_node->list); batadv_neigh_node_put(neigh_node); + + atomic_dec(&orig_node->bat_priv->neigh_learned); } hlist_for_each_entry_safe(orig_ifinfo, node_tmp, @@ -1144,6 +1155,7 @@ batadv_purge_orig_neighbors(struct batadv_priv *bat_priv, hlist_del_rcu(&neigh_node->list); batadv_neigh_node_put(neigh_node); + atomic_dec(&bat_priv->neigh_learned); } else { /* only necessary if not the whole neighbor is to be * deleted, but some interface has been removed. diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h index c8c3e806..13349350 100644 --- a/net/batman-adv/types.h +++ b/net/batman-adv/types.h @@ -1637,6 +1637,12 @@ struct batadv_priv { /** @meshif_vlan_list_lock: lock protecting meshif_vlan_list */ spinlock_t meshif_vlan_list_lock; + /** @neigh_max_learned: Maximum number of neighbors */ + u32 neigh_max_learned; + + /** @neigh_learned: current number of learned neighbors */ + atomic_t neigh_learned; + #ifdef CONFIG_BATMAN_ADV_BLA /** @bla: bridge loop avoidance data */ struct batadv_priv_bla bla; -- 2.47.3
