The pointer batadv_bla_claim::backbone_gw can be changed at any time. Therefore, access to it must be protected to ensure that two function accessing the same backbone_gw are actually accessing the same. This is especially important when the crc_lock is used or when the backbone_gw of a claim is exchanged.

Not doing so leads to invalid memory access and/or reference leaks.

Fixes: a9ce0dc43e2c ("batman-adv: add basic bridge loop avoidance code") Fixes: b307e72d119f ("batman-adv: lock crc access in bridge loop avoidance") Signed-off-by: Sven Eckelmann sven@narfation.org --- v3: - rename batadv_bla_claim_backbone_gw to batadv_bla_claim_get_backbone_gw v2: - Move backbone release of claim to batadv_claim_release - added kerneldoc for backbone_lock --- net/batman-adv/bridge_loop_avoidance.c | 111 ++++++++++++++++++++++++++------- net/batman-adv/types.h | 2 + 2 files changed, 90 insertions(+), 23 deletions(-)

diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c index 748a9ea..a796bde 100644 --- a/net/batman-adv/bridge_loop_avoidance.c +++ b/net/batman-adv/bridge_loop_avoidance.c @@ -177,10 +177,21 @@ static void batadv_backbone_gw_put(struct batadv_bla_backbone_gw *backbone_gw) static void batadv_claim_release(struct kref *ref) { struct batadv_bla_claim *claim; + struct batadv_bla_backbone_gw *old_backbone_gw;

claim = container_of(ref, struct batadv_bla_claim, refcount);

- batadv_backbone_gw_put(claim->backbone_gw); + spin_lock_bh(&claim->backbone_lock); + old_backbone_gw = claim->backbone_gw; + claim->backbone_gw = NULL; + spin_unlock_bh(&claim->backbone_lock); + + spin_lock_bh(&old_backbone_gw->crc_lock); + old_backbone_gw->crc ^= crc16(0, claim->addr, ETH_ALEN); + spin_unlock_bh(&old_backbone_gw->crc_lock); + + batadv_backbone_gw_put(old_backbone_gw); + kfree_rcu(claim, rcu); }

@@ -674,8 +685,10 @@ static void batadv_bla_add_claim(struct batadv_priv *bat_priv, const u8 *mac, const unsigned short vid, struct batadv_bla_backbone_gw *backbone_gw) { + struct batadv_bla_backbone_gw *old_backbone_gw; struct batadv_bla_claim *claim; struct batadv_bla_claim search_claim; + bool remove_crc = false; int hash_added;

ether_addr_copy(search_claim.addr, mac); @@ -689,8 +702,10 @@ static void batadv_bla_add_claim(struct batadv_priv *bat_priv, return;

ether_addr_copy(claim->addr, mac); + spin_lock_init(&claim->backbone_lock); claim->vid = vid; claim->lasttime = jiffies; + kref_get(&backbone_gw->refcount); claim->backbone_gw = backbone_gw;

kref_init(&claim->refcount); @@ -718,15 +733,26 @@ static void batadv_bla_add_claim(struct batadv_priv *bat_priv, "bla_add_claim(): changing ownership for %pM, vid %d\n", mac, BATADV_PRINT_VID(vid));

- spin_lock_bh(&claim->backbone_gw->crc_lock); - claim->backbone_gw->crc ^= crc16(0, claim->addr, ETH_ALEN); - spin_unlock_bh(&claim->backbone_gw->crc_lock); - batadv_backbone_gw_put(claim->backbone_gw); + remove_crc = true; } - /* set (new) backbone gw */ + + /* replace backbone_gw atomically and adjust reference counters */ + spin_lock_bh(&claim->backbone_lock); + old_backbone_gw = claim->backbone_gw; kref_get(&backbone_gw->refcount); claim->backbone_gw = backbone_gw; + spin_unlock_bh(&claim->backbone_lock); + + if (remove_crc) { + /* remove claim address from old backbone_gw */ + spin_lock_bh(&old_backbone_gw->crc_lock); + old_backbone_gw->crc ^= crc16(0, claim->addr, ETH_ALEN); + spin_unlock_bh(&old_backbone_gw->crc_lock); + }

+ batadv_backbone_gw_put(old_backbone_gw); + + /* add claim address to new backbone_gw */ spin_lock_bh(&backbone_gw->crc_lock); backbone_gw->crc ^= crc16(0, claim->addr, ETH_ALEN); spin_unlock_bh(&backbone_gw->crc_lock); @@ -737,6 +763,26 @@ claim_free_ref: }

/** + * batadv_bla_claim_get_backbone_gw - Get valid reference for backbone_gw of + * claim + * @claim: claim whose backbone_gw should be returned + * + * Return: valid reference to claim::backbone_gw + */ +static struct batadv_bla_backbone_gw * +batadv_bla_claim_get_backbone_gw(struct batadv_bla_claim *claim) +{ + struct batadv_bla_backbone_gw *backbone_gw; + + spin_lock_bh(&claim->backbone_lock); + backbone_gw = claim->backbone_gw; + kref_get(&backbone_gw->refcount); + spin_unlock_bh(&claim->backbone_lock); + + return backbone_gw; +} + +/** * batadv_bla_del_claim - delete a claim from the claim hash * @bat_priv: the bat priv with all the soft interface information * @mac: mac address of the claim to be removed @@ -760,10 +806,6 @@ static void batadv_bla_del_claim(struct batadv_priv *bat_priv, batadv_choose_claim, claim); batadv_claim_put(claim); /* reference from the hash is gone */

- spin_lock_bh(&claim->backbone_gw->crc_lock); - claim->backbone_gw->crc ^= crc16(0, claim->addr, ETH_ALEN); - spin_unlock_bh(&claim->backbone_gw->crc_lock); - /* don't need the reference from hash_find() anymore */ batadv_claim_put(claim); } @@ -1216,6 +1258,7 @@ static void batadv_bla_purge_claims(struct batadv_priv *bat_priv, struct batadv_hard_iface *primary_if, int now) { + struct batadv_bla_backbone_gw *backbone_gw; struct batadv_bla_claim *claim; struct hlist_head *head; struct batadv_hashtable *hash; @@ -1230,14 +1273,17 @@ static void batadv_bla_purge_claims(struct batadv_priv *bat_priv,

rcu_read_lock(); hlist_for_each_entry_rcu(claim, head, hash_entry) { + backbone_gw = batadv_bla_claim_get_backbone_gw(claim); if (now) goto purge_now; - if (!batadv_compare_eth(claim->backbone_gw->orig, + + if (!batadv_compare_eth(backbone_gw->orig, primary_if->net_dev->dev_addr)) - continue; + goto skip; + if (!batadv_has_timed_out(claim->lasttime, BATADV_BLA_CLAIM_TIMEOUT)) - continue; + goto skip;

batadv_dbg(BATADV_DBG_BLA, bat_priv, "bla_purge_claims(): %pM, vid %d, time out\n", @@ -1245,8 +1291,10 @@ static void batadv_bla_purge_claims(struct batadv_priv *bat_priv,

purge_now: batadv_handle_unclaim(bat_priv, primary_if, - claim->backbone_gw->orig, + backbone_gw->orig, claim->addr, claim->vid); +skip: + batadv_backbone_gw_put(backbone_gw); } rcu_read_unlock(); } @@ -1757,9 +1805,11 @@ batadv_bla_loopdetect_check(struct batadv_priv *bat_priv, struct sk_buff *skb, bool batadv_bla_rx(struct batadv_priv *bat_priv, struct sk_buff *skb, unsigned short vid, bool is_bcast) { + struct batadv_bla_backbone_gw *backbone_gw; struct ethhdr *ethhdr; struct batadv_bla_claim search_claim, *claim = NULL; struct batadv_hard_iface *primary_if; + bool own_claim; bool ret;

ethhdr = eth_hdr(skb); @@ -1794,8 +1844,12 @@ bool batadv_bla_rx(struct batadv_priv *bat_priv, struct sk_buff *skb, }

/* if it is our own claim ... */ - if (batadv_compare_eth(claim->backbone_gw->orig, - primary_if->net_dev->dev_addr)) { + backbone_gw = batadv_bla_claim_get_backbone_gw(claim); + own_claim = batadv_compare_eth(backbone_gw->orig, + primary_if->net_dev->dev_addr); + batadv_backbone_gw_put(backbone_gw); + + if (own_claim) { /* ... allow it in any case */ claim->lasttime = jiffies; goto allow; @@ -1859,7 +1913,9 @@ bool batadv_bla_tx(struct batadv_priv *bat_priv, struct sk_buff *skb, { struct ethhdr *ethhdr; struct batadv_bla_claim search_claim, *claim = NULL; + struct batadv_bla_backbone_gw *backbone_gw; struct batadv_hard_iface *primary_if; + bool client_roamed; bool ret = false;

primary_if = batadv_primary_if_get_selected(bat_priv); @@ -1889,8 +1945,12 @@ bool batadv_bla_tx(struct batadv_priv *bat_priv, struct sk_buff *skb, goto allow;

/* check if we are responsible. */ - if (batadv_compare_eth(claim->backbone_gw->orig, - primary_if->net_dev->dev_addr)) { + backbone_gw = batadv_bla_claim_get_backbone_gw(claim); + client_roamed = batadv_compare_eth(backbone_gw->orig, + primary_if->net_dev->dev_addr); + batadv_backbone_gw_put(backbone_gw); + + if (client_roamed) { /* if yes, the client has roamed and we have * to unclaim it. */ @@ -1938,6 +1998,7 @@ int batadv_bla_claim_table_seq_print_text(struct seq_file *seq, void *offset) struct net_device *net_dev = (struct net_device *)seq->private; struct batadv_priv *bat_priv = netdev_priv(net_dev); struct batadv_hashtable *hash = bat_priv->bla.claim_hash; + struct batadv_bla_backbone_gw *backbone_gw; struct batadv_bla_claim *claim; struct batadv_hard_iface *primary_if; struct hlist_head *head; @@ -1962,17 +2023,21 @@ int batadv_bla_claim_table_seq_print_text(struct seq_file *seq, void *offset)

rcu_read_lock(); hlist_for_each_entry_rcu(claim, head, hash_entry) { - is_own = batadv_compare_eth(claim->backbone_gw->orig, + backbone_gw = batadv_bla_claim_get_backbone_gw(claim); + + is_own = batadv_compare_eth(backbone_gw->orig, primary_addr);

- spin_lock_bh(&claim->backbone_gw->crc_lock); - backbone_crc = claim->backbone_gw->crc; - spin_unlock_bh(&claim->backbone_gw->crc_lock); + spin_lock_bh(&backbone_gw->crc_lock); + backbone_crc = backbone_gw->crc; + spin_unlock_bh(&backbone_gw->crc_lock); seq_printf(seq, " * %pM on %5d by %pM [%c] (%#.4x)\n", claim->addr, BATADV_PRINT_VID(claim->vid), - claim->backbone_gw->orig, + backbone_gw->orig, (is_own ? 'x' : ' '), backbone_crc); + + batadv_backbone_gw_put(backbone_gw); } rcu_read_unlock(); } diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h index ba846b0..0051222 100644 --- a/net/batman-adv/types.h +++ b/net/batman-adv/types.h @@ -1042,6 +1042,7 @@ struct batadv_bla_backbone_gw { * @addr: mac address of claimed non-mesh client * @vid: vlan id this client was detected on * @backbone_gw: pointer to backbone gw claiming this client + * @backbone_lock: lock protecting backbone_gw pointer * @lasttime: last time we heard of claim (locals only) * @hash_entry: hlist node for batadv_priv_bla::claim_hash * @refcount: number of contexts the object is used @@ -1051,6 +1052,7 @@ struct batadv_bla_claim { u8 addr[ETH_ALEN]; unsigned short vid; struct batadv_bla_backbone_gw *backbone_gw; + spinlock_t backbone_lock; /* protects backbone_gw */ unsigned long lasttime; struct hlist_node hash_entry; struct rcu_head rcu;

Acked-by: Simon Wunderlich sw@simonwunderlich.de

Thanks, this also looks much cleaner now! Simon

On Thursday 30 June 2016 20:11:34 Sven Eckelmann wrote:

The replacement of last_bonding_candidate in batadv_orig_node has to be an atomic operation. Otherwise it is possible that the reference counter of a batadv_orig_ifinfo is reduced which was no longer the last_bonding_candidate when the new candidate is added. This can either lead to an invalid memory access or to reference leaks which make it impossible to an interface which was added to batman-adv.

Fixes: 797edd9e87ac ("batman-adv: add bonding again") Signed-off-by: Sven Eckelmann sven@narfation.org

---

v2:

• get refcnt for new selected router before assigning it to returned variable
• move refcnt cleanup of all remembered candidates/routers to central place

---

net/batman-adv/routing.c | 52 ++++++++++++++++++++++++++++++++++++------------ net/batman-adv/types.h | 4 +++- 2 files changed, 42 insertions(+), 14 deletions(-)

diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c index bba9276..a4253d4 100644 --- a/net/batman-adv/routing.c +++ b/net/batman-adv/routing.c @@ -462,6 +462,29 @@ static int batadv_check_unicast_packet(struct batadv_priv *bat_priv, }

/**

• • batadv_last_bonding_replace - Replace last_bonding_candidate of

orig_node + * @orig_node: originator node whose bonding candidates should be replaced + * @new_candidate: new bonding candidate or NULL

• */

+static void +batadv_last_bonding_replace(struct batadv_orig_node *orig_node,

• 	    struct batadv_orig_ifinfo *new_candidate)
  

+{

• struct batadv_orig_ifinfo *old_candidate;
• spin_lock_bh(&orig_node->neigh_list_lock);
• old_candidate = orig_node->last_bonding_candidate;
• if (new_candidate)

• kref_get(&new_candidate->refcount);
  

• orig_node->last_bonding_candidate = new_candidate;
• spin_unlock_bh(&orig_node->neigh_list_lock);
• if (old_candidate)

• batadv_orig_ifinfo_put(old_candidate);
  

+}

+/**

• batadv_find_router - find a suitable router for this originator
• @bat_priv: the bat priv with all the soft interface information
• @orig_node: the destination node

@@ -568,10 +591,6 @@ next: } rcu_read_unlock();

• /* last_bonding_candidate is reset below, remove the old reference. */
• if (orig_node->last_bonding_candidate)

• batadv_orig_ifinfo_put(orig_node->last_bonding_candidate);
  

• /* After finding candidates, handle the three cases:
  • 1. there is a next candidate, use that
  • 2. there is no next candidate, use the first of the list

@@ -580,21 +599,28 @@ next: if (next_candidate) { batadv_neigh_node_put(router);

• /* remove references to first candidate, we don't need it. */
  

• if (first_candidate) {
  

• 	batadv_neigh_node_put(first_candidate_router);
  

• 	batadv_orig_ifinfo_put(first_candidate);
  

• }
  

• kref_get(&next_candidate_router->refcount);
  

  router = next_candidate_router;

• orig_node->last_bonding_candidate = next_candidate;
  

• batadv_last_bonding_replace(orig_node, next_candidate);
  

  } else if (first_candidate) { batadv_neigh_node_put(router);

• /* refcounting has already been done in the loop above. */
  

• kref_get(&first_candidate_router->refcount);
  

  router = first_candidate_router;

• orig_node->last_bonding_candidate = first_candidate;
  

• batadv_last_bonding_replace(orig_node, first_candidate);
  

  } else {

• orig_node->last_bonding_candidate = NULL;
  

• batadv_last_bonding_replace(orig_node, NULL);
  

• }

• /* cleanup of candidates */

• if (first_candidate) {

• batadv_neigh_node_put(first_candidate_router);
  

• batadv_orig_ifinfo_put(first_candidate);
  

• }

• if (next_candidate) {

• batadv_neigh_node_put(next_candidate_router);
  

• batadv_orig_ifinfo_put(next_candidate);
  

  }

  return router;

diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h index d82f6b4..96af6da 100644 --- a/net/batman-adv/types.h +++ b/net/batman-adv/types.h @@ -329,7 +329,9 @@ struct batadv_orig_node { DECLARE_BITMAP(bcast_bits, BATADV_TQ_LOCAL_WINDOW_SIZE); u32 last_bcast_seqno; struct hlist_head neigh_list;

• /* neigh_list_lock protects: neigh_list and router */

• /* neigh_list_lock protects: neigh_list, ifinfo_list,

• * last_bonding_candidate and router
  

• */
  

  spinlock_t neigh_list_lock; struct hlist_node hash_entry; struct batadv_priv *bat_priv;