mac80211: atomically check whether STA exists already
When a STA structure is added, it is often checked whether it
already exists before adding it. This, however, isn't done
atomically so there is a race condition that could lead to two
STA structures being added with the same MAC address. This
patch changes sta_info_add() to return an ERR_PTR in case
of failure and adds the failure mode -EEXIST when the STA
already exists.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: Luis Carlos Cobo <luisca@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index a083cc7..b0c41a0 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -562,13 +562,6 @@
if (!netif_running(dev))
return -ENETDOWN;
- /* XXX: get sta belonging to dev */
- sta = sta_info_get(local, mac);
- if (sta) {
- sta_info_put(sta);
- return -EEXIST;
- }
-
if (params->vlan) {
sdata = IEEE80211_DEV_TO_SUB_IF(params->vlan);
@@ -579,8 +572,8 @@
sdata = IEEE80211_DEV_TO_SUB_IF(dev);
sta = sta_info_add(local, dev, mac, GFP_KERNEL);
- if (!sta)
- return -ENOMEM;
+ if (IS_ERR(sta))
+ return PTR_ERR(sta);
sta->dev = sdata->dev;
if (sdata->vif.type == IEEE80211_IF_TYPE_VLAN ||
diff --git a/net/mac80211/ieee80211.c b/net/mac80211/ieee80211.c
index a00858d..f82ebdd 100644
--- a/net/mac80211/ieee80211.c
+++ b/net/mac80211/ieee80211.c
@@ -838,8 +838,8 @@
/* Create STA entry for the new peer */
sta = sta_info_add(local, dev, remote_addr, GFP_KERNEL);
- if (!sta)
- return -ENOMEM;
+ if (IS_ERR(sta))
+ return PTR_ERR(sta);
sta->flags |= WLAN_STA_AUTHORIZED;
diff --git a/net/mac80211/ieee80211_sta.c b/net/mac80211/ieee80211_sta.c
index 8d620ba..64476d9 100644
--- a/net/mac80211/ieee80211_sta.c
+++ b/net/mac80211/ieee80211_sta.c
@@ -1807,9 +1807,9 @@
if (!sta) {
struct ieee80211_sta_bss *bss;
sta = sta_info_add(local, dev, ifsta->bssid, GFP_KERNEL);
- if (!sta) {
+ if (IS_ERR(sta)) {
printk(KERN_DEBUG "%s: failed to add STA entry for the"
- " AP\n", dev->name);
+ " AP (error %ld)\n", dev->name, PTR_ERR(sta));
return;
}
bss = ieee80211_rx_bss_get(dev, ifsta->bssid,
@@ -3820,7 +3820,7 @@
wiphy_name(local->hw.wiphy), print_mac(mac, addr), dev->name);
sta = sta_info_add(local, dev, addr, GFP_ATOMIC);
- if (!sta)
+ if (IS_ERR(sta))
return NULL;
sta->flags |= WLAN_STA_AUTHORIZED;
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index b31a627..c6c0df4 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -55,19 +55,29 @@
return -ENOENT;
}
+/* must hold local->sta_lock */
+static struct sta_info *__sta_info_find(struct ieee80211_local *local,
+ u8 *addr)
+{
+ struct sta_info *sta;
+
+ sta = local->sta_hash[STA_HASH(addr)];
+ while (sta) {
+ if (compare_ether_addr(sta->addr, addr) == 0)
+ break;
+ sta = sta->hnext;
+ }
+ return sta;
+}
+
struct sta_info *sta_info_get(struct ieee80211_local *local, u8 *addr)
{
struct sta_info *sta;
read_lock_bh(&local->sta_lock);
- sta = local->sta_hash[STA_HASH(addr)];
- while (sta) {
- if (memcmp(sta->addr, addr, ETH_ALEN) == 0) {
- __sta_info_get(sta);
- break;
- }
- sta = sta->hnext;
- }
+ sta = __sta_info_find(local, addr);
+ if (sta)
+ __sta_info_get(sta);
read_unlock_bh(&local->sta_lock);
return sta;
@@ -110,8 +120,8 @@
EXPORT_SYMBOL(sta_info_put);
-struct sta_info * sta_info_add(struct ieee80211_local *local,
- struct net_device *dev, u8 *addr, gfp_t gfp)
+struct sta_info *sta_info_add(struct ieee80211_local *local,
+ struct net_device *dev, u8 *addr, gfp_t gfp)
{
struct sta_info *sta;
int i;
@@ -119,7 +129,7 @@
sta = kzalloc(sizeof(*sta), gfp);
if (!sta)
- return NULL;
+ return ERR_PTR(-ENOMEM);
kref_init(&sta->kref);
@@ -128,7 +138,7 @@
if (!sta->rate_ctrl_priv) {
rate_control_put(sta->rate_ctrl);
kfree(sta);
- return NULL;
+ return ERR_PTR(-ENOMEM);
}
memcpy(sta->addr, addr, ETH_ALEN);
@@ -158,9 +168,15 @@
}
skb_queue_head_init(&sta->ps_tx_buf);
skb_queue_head_init(&sta->tx_filtered);
- __sta_info_get(sta); /* sta used by caller, decremented by
- * sta_info_put() */
write_lock_bh(&local->sta_lock);
+ /* mark sta as used (by caller) */
+ __sta_info_get(sta);
+ /* check if STA exists already */
+ if (__sta_info_find(local, addr)) {
+ write_unlock_bh(&local->sta_lock);
+ sta_info_put(sta);
+ return ERR_PTR(-EEXIST);
+ }
list_add(&sta->list, &local->sta_list);
local->num_sta++;
sta_info_hash_add(local, sta);
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index f7e65fa..7b5be30 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -239,8 +239,8 @@
struct sta_info * sta_info_get(struct ieee80211_local *local, u8 *addr);
void sta_info_put(struct sta_info *sta);
-struct sta_info * sta_info_add(struct ieee80211_local *local,
- struct net_device *dev, u8 *addr, gfp_t gfp);
+struct sta_info *sta_info_add(struct ieee80211_local *local,
+ struct net_device *dev, u8 *addr, gfp_t gfp);
void sta_info_remove(struct sta_info *sta);
void sta_info_free(struct sta_info *sta);
void sta_info_init(struct ieee80211_local *local);