From patchwork Wed Jan 29 10:25:12 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Antonio Quartulli X-Patchwork-Id: 3800 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=178.209.62.157; helo=s3.neomailbox.net; envelope-from=antonio@meshcoding.com; receiver=b.a.t.m.a.n@lists.open-mesh.org Received: from s3.neomailbox.net (s3.neomailbox.net [178.209.62.157]) by open-mesh.org (Postfix) with ESMTPS id 3C2C7602368 for ; Wed, 29 Jan 2014 11:26:32 +0100 (CET) From: Antonio Quartulli To: b.a.t.m.a.n@lists.open-mesh.org Date: Wed, 29 Jan 2014 11:25:12 +0100 Message-Id: <1390991112-2494-1-git-send-email-antonio@meshcoding.com> Cc: Antonio Quartulli Subject: [B.A.T.M.A.N.] [PATCHv4] batman-adv: avoid potential race condition when adding a new neighbour X-BeenThere: b.a.t.m.a.n@lists.open-mesh.org X-Mailman-Version: 2.1.15 Precedence: list Reply-To: The list for a Better Approach To Mobile Ad-hoc Networking List-Id: The list for a Better Approach To Mobile Ad-hoc Networking List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 29 Jan 2014 10:26:32 -0000 From: Antonio Quartulli When adding a new neighbour it is important to atomically perform the following: - check if the neighbour already exists - append the neighbour to the proper list If the two operations are not performed in an atomic context it is possible that two concurrent insertions add the same neighbour twice. Signed-off-by: Antonio Quartulli --- Changes from v3: - remove useless initialization Changes from v2: - fix typ0 Changes from v1: - release hard_iface if we already have a matching neighbour bat_iv_ogm.c | 22 ++++++++++++++++------ originator.c | 36 ++++++++++++++++++++++++++++++++++++ originator.h | 4 ++++ 3 files changed, 56 insertions(+), 6 deletions(-) diff --git a/bat_iv_ogm.c b/bat_iv_ogm.c index 512159b..094ae7c 100644 --- a/bat_iv_ogm.c +++ b/bat_iv_ogm.c @@ -266,7 +266,7 @@ batadv_iv_ogm_neigh_new(struct batadv_hard_iface *hard_iface, struct batadv_orig_node *orig_neigh) { struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface); - struct batadv_neigh_node *neigh_node; + struct batadv_neigh_node *neigh_node, *tmp_neigh_node; neigh_node = batadv_neigh_node_new(hard_iface, neigh_addr, orig_node); if (!neigh_node) @@ -281,14 +281,24 @@ batadv_iv_ogm_neigh_new(struct batadv_hard_iface *hard_iface, neigh_node->orig_node = orig_neigh; neigh_node->if_incoming = hard_iface; - batadv_dbg(BATADV_DBG_BATMAN, bat_priv, - "Creating new neighbor %pM for orig_node %pM on interface %s\n", - neigh_addr, orig_node->orig, hard_iface->net_dev->name); - spin_lock_bh(&orig_node->neigh_list_lock); - hlist_add_head_rcu(&neigh_node->list, &orig_node->neigh_list); + tmp_neigh_node = batadv_neigh_node_get(orig_node, hard_iface, + neigh_addr); + if (!tmp_neigh_node) { + hlist_add_head_rcu(&neigh_node->list, &orig_node->neigh_list); + } else { + kfree(neigh_node); + batadv_hardif_free_ref(hard_iface); + neigh_node = tmp_neigh_node; + } spin_unlock_bh(&orig_node->neigh_list_lock); + if (!tmp_neigh_node) + batadv_dbg(BATADV_DBG_BATMAN, bat_priv, + "Creating new neighbor %pM for orig_node %pM on interface %s\n", + neigh_addr, orig_node->orig, + hard_iface->net_dev->name); + out: return neigh_node; } diff --git a/originator.c b/originator.c index 6df12a2..8539416 100644 --- a/originator.c +++ b/originator.c @@ -458,6 +458,42 @@ out: } /** + * batadv_neigh_node_get - retrieve a neighbour from the list + * @orig_node: originator which the neighbour belongs to + * @hard_iface: the interface where this neighbour is connected to + * @addr: the address of the neighbour + * + * Looks for and possibly returns a neighbour belonging to this originator list + * which is connected through the provided hard interface. + * Returns NULL if the neighbour is not found. + */ +struct batadv_neigh_node * +batadv_neigh_node_get(const struct batadv_orig_node *orig_node, + const struct batadv_hard_iface *hard_iface, + const uint8_t *addr) +{ + struct batadv_neigh_node *tmp_neigh_node, *res = NULL; + + rcu_read_lock(); + hlist_for_each_entry_rcu(tmp_neigh_node, &orig_node->neigh_list, list) { + if (!batadv_compare_eth(tmp_neigh_node->addr, addr)) + continue; + + if (tmp_neigh_node->if_incoming != hard_iface) + continue; + + if (!atomic_inc_not_zero(&tmp_neigh_node->refcount)) + continue; + + res = tmp_neigh_node; + break; + } + rcu_read_unlock(); + + return res; +} + +/** * batadv_orig_ifinfo_free_rcu - free the orig_ifinfo object * @rcu: rcu pointer of the orig_ifinfo object */ diff --git a/originator.h b/originator.h index 37be290..db3a9ed 100644 --- a/originator.h +++ b/originator.h @@ -29,6 +29,10 @@ void batadv_orig_node_free_ref_now(struct batadv_orig_node *orig_node); struct batadv_orig_node *batadv_orig_node_new(struct batadv_priv *bat_priv, const uint8_t *addr); struct batadv_neigh_node * +batadv_neigh_node_get(const struct batadv_orig_node *orig_node, + const struct batadv_hard_iface *hard_iface, + const uint8_t *addr); +struct batadv_neigh_node * batadv_neigh_node_new(struct batadv_hard_iface *hard_iface, const uint8_t *neigh_addr, struct batadv_orig_node *orig_node);