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Message-ID: <lsq.1479082460.67864198@decadent.org.uk>
Date: Mon, 14 Nov 2016 00:14:20 +0000
From: Ben Hutchings <ben@...adent.org.uk>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC: akpm@...ux-foundation.org, "Sven Eckelmann" <sven@...fation.org>,
"Simon Wunderlich" <sw@...onwunderlich.de>,
"Marek Lindner" <mareklindner@...mailbox.ch>
Subject: [PATCH 3.16 039/346] batman-adv: Fix non-atomic bla_claim::backbone_gw
access
3.16.39-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Sven Eckelmann <sven@...fation.org>
commit 3db0decf1185357d6ab2256d0dede1ca9efda03d upstream.
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: 23721387c409 ("batman-adv: add basic bridge loop avoidance code")
Fixes: 5a1dd8a4773d ("batman-adv: lock crc access in bridge loop avoidance")
Signed-off-by: Sven Eckelmann <sven@...fation.org>
Signed-off-by: Marek Lindner <mareklindner@...mailbox.ch>
Signed-off-by: Simon Wunderlich <sw@...onwunderlich.de>
[bwh: Backported to 3.16:
- s/kref_get/atomic_inc/
- s/_put/_free_ref/
- Adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
net/batman-adv/bridge_loop_avoidance.c | 111 ++++++++++++++++++++++++++-------
net/batman-adv/types.h | 2 +
2 files changed, 90 insertions(+), 23 deletions(-)
--- a/net/batman-adv/bridge_loop_avoidance.c
+++ b/net/batman-adv/bridge_loop_avoidance.c
@@ -115,7 +115,18 @@ batadv_backbone_gw_free_ref(struct batad
/* finally deinitialize the claim */
static void batadv_claim_release(struct batadv_bla_claim *claim)
{
- batadv_backbone_gw_free_ref(claim->backbone_gw);
+ struct batadv_bla_backbone_gw *old_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_free_ref(old_backbone_gw);
+
kfree_rcu(claim, rcu);
}
@@ -563,8 +574,10 @@ static void batadv_bla_add_claim(struct
const uint8_t *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);
@@ -578,8 +591,10 @@ static void batadv_bla_add_claim(struct
return;
ether_addr_copy(claim->addr, mac);
+ spin_lock_init(&claim->backbone_lock);
claim->vid = vid;
claim->lasttime = jiffies;
+ atomic_inc(&backbone_gw->refcount);
claim->backbone_gw = backbone_gw;
atomic_set(&claim->refcount, 2);
@@ -606,15 +621,26 @@ static void batadv_bla_add_claim(struct
"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_free_ref(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;
atomic_inc(&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_free_ref(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);
@@ -624,6 +650,26 @@ claim_free_ref:
batadv_claim_free_ref(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;
+ atomic_inc(&backbone_gw->refcount);
+ spin_unlock_bh(&claim->backbone_lock);
+
+ return backbone_gw;
+}
+
/* Delete a claim from the claim hash which has the
* given mac address and vid.
*/
@@ -645,10 +691,6 @@ static void batadv_bla_del_claim(struct
batadv_choose_claim, claim);
batadv_claim_free_ref(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_free_ref(claim);
}
@@ -1059,6 +1101,7 @@ static void batadv_bla_purge_claims(stru
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;
@@ -1073,14 +1116,17 @@ static void batadv_bla_purge_claims(stru
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",
@@ -1088,8 +1134,10 @@ static void batadv_bla_purge_claims(stru
purge_now:
batadv_handle_unclaim(bat_priv, primary_if,
- claim->backbone_gw->orig,
+ backbone_gw->orig,
claim->addr, claim->vid);
+skip:
+ batadv_backbone_gw_free_ref(backbone_gw);
}
rcu_read_unlock();
}
@@ -1476,9 +1524,11 @@ void batadv_bla_free(struct batadv_priv
int 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;
int ret;
ethhdr = eth_hdr(skb);
@@ -1511,8 +1561,12 @@ int batadv_bla_rx(struct batadv_priv *ba
}
/* 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_free_ref(backbone_gw);
+
+ if (own_claim) {
/* ... allow it in any case */
claim->lasttime = jiffies;
goto allow;
@@ -1575,7 +1629,9 @@ int batadv_bla_tx(struct batadv_priv *ba
{
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;
int ret = 0;
primary_if = batadv_primary_if_get_selected(bat_priv);
@@ -1605,8 +1661,12 @@ int batadv_bla_tx(struct batadv_priv *ba
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_free_ref(backbone_gw);
+
+ if (client_roamed) {
/* if yes, the client has roamed and we have
* to unclaim it.
*/
@@ -1647,6 +1707,7 @@ int batadv_bla_claim_table_seq_print_tex
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;
@@ -1671,17 +1732,21 @@ int batadv_bla_claim_table_seq_print_tex
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_free_ref(backbone_gw);
}
rcu_read_unlock();
}
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -895,6 +895,7 @@ 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
@@ -904,6 +905,7 @@ struct batadv_bla_claim {
uint8_t 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;
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