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batman-adv: Fix non-atomic bla_claim::backbone_gw access 

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: 23721387c4 ("batman-adv: add basic bridge loop avoidance code")
Fixes: 5a1dd8a477 ("batman-adv: lock crc access in bridge loop avoidance")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
This commit is contained in:
Sven Eckelmann 2016-07-01 15:49:43 +02:00 committed by Simon Wunderlich
parent 33fbb1f3db
commit 3db0decf11
2 changed files with 90 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

111
net/batman-adv/bridge_loop_avoidance.c
View File

@ -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);
}
@ -677,8 +688,10 @@ 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);
@ -692,8 +705,10 @@ 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);
@ -721,15 +736,26 @@ 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);
@ -739,6 +765,26 @@ static void batadv_bla_add_claim(struct batadv_priv *bat_priv,
batadv_claim_put(claim);
}
/**
* 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
@ -763,10 +809,6 @@ 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);
}
@ -1219,6 +1261,7 @@ 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;
@ -1233,14 +1276,17 @@ 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",
@ -1248,8 +1294,10 @@ 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();
}
@ -1760,9 +1808,11 @@ 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);
@ -1797,8 +1847,12 @@ 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;
@ -1862,7 +1916,9 @@ 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);
@ -1892,8 +1948,12 @@ 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.
*/
@ -1941,6 +2001,7 @@ 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;
@ -1965,17 +2026,21 @@ 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();
}

2
net/batman-adv/types.h
View File

@ -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;