sta_info_add() has two functions: allocating a station info
structure and inserting it into the hash table/list. Splitting
these two functions allows allocating with GFP_KERNEL in many
places instead of GFP_ATOMIC which is now required by the RCU
protection. Additionally, in many places RCU protection is now
no longer needed at all because between sta_info_alloc() and
sta_info_insert() the caller owns the structure.
This fixes a few race conditions with setting initial flags
and similar, but not all (see comments in ieee80211_sta.c and
cfg.c).
Signed-off-by: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
---
net/mac80211/cfg.c | 38 ++++++++++++++++-------
net/mac80211/ieee80211.c | 18 ++++++-----
net/mac80211/ieee80211_sta.c | 44 ++++++++++++++++++++-------
net/mac80211/sta_info.c | 69 +++++++++++++++++++++++++++++--------------
net/mac80211/sta_info.h | 17 +++++++---
5 files changed, 129 insertions(+), 57 deletions(-)
--- everything.orig/net/mac80211/sta_info.c 2008-02-22 11:53:23.000000000 +0100
+++ everything/net/mac80211/sta_info.c 2008-02-22 11:54:34.000000000 +0100
@@ -29,12 +29,13 @@
* for faster lookup and a list for iteration. They are managed using
* RCU, i.e. access to the list and hash table is protected by RCU.
*
- * STA info structures are always "alive" when they are added with
- * @sta_info_add() [this may be changed in the future to allow allocating
- * outside of a critical section!], they are then added to the hash
- * table and list. Therefore, @sta_info_add() must also be RCU protected,
- * also, the caller of @sta_info_add() cannot assume that it owns the
- * structure.
+ * Upon allocating a STA info structure with @sta_info_alloc(), the
+ * caller owns that structure. It must then either destroy it using
+ * @sta_info_destroy() (which is pretty useless) or insert it into
+ * the hash table using @sta_info_insert() which demotes the reference
+ * from ownership to a regular RCU-protected reference, if the function
+ * is called without protection by an RCU critical section the reference
+ * is instantly invalidated.
*
* Because there are debugfs entries for each station, and adding those
* must be able to sleep, it is also possible to "pin" a station entry,
@@ -112,6 +113,10 @@ void sta_info_destroy(struct sta_info *s
struct ieee80211_local *local = sta->local;
struct sk_buff *skb;
int i;
+ DECLARE_MAC_BUF(mbuf);
+
+ if (!sta)
+ return;
ieee80211_key_free(sta->key);
sta->key = NULL;
@@ -134,6 +139,11 @@ void sta_info_destroy(struct sta_info *s
rate_control_free_sta(sta->rate_ctrl, sta->rate_ctrl_priv);
rate_control_put(sta->rate_ctrl);
+#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
+ printk(KERN_DEBUG "%s: Destroyed STA %s\n",
+ wiphy_name(local->hw.wiphy), print_mac(mbuf, sta->addr));
+#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
+
kfree(sta);
}
@@ -146,18 +156,17 @@ static void sta_info_hash_add(struct iee
rcu_assign_pointer(local->sta_hash[STA_HASH(sta->addr)], sta);
}
-struct sta_info *sta_info_add(struct ieee80211_sub_if_data *sdata,
- u8 *addr)
+struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
+ u8 *addr, gfp_t gfp)
{
struct ieee80211_local *local = sdata->local;
struct sta_info *sta;
int i;
- DECLARE_MAC_BUF(mac);
- unsigned long flags;
+ DECLARE_MAC_BUF(mbuf);
- sta = kzalloc(sizeof(*sta), GFP_ATOMIC);
+ sta = kzalloc(sizeof(*sta), gfp);
if (!sta)
- return ERR_PTR(-ENOMEM);
+ return NULL;
memcpy(sta->addr, addr, ETH_ALEN);
sta->local = local;
@@ -165,11 +174,11 @@ struct sta_info *sta_info_add(struct iee
sta->rate_ctrl = rate_control_get(local->rate_ctrl);
sta->rate_ctrl_priv = rate_control_alloc_sta(sta->rate_ctrl,
- GFP_ATOMIC);
+ gfp);
if (!sta->rate_ctrl_priv) {
rate_control_put(sta->rate_ctrl);
kfree(sta);
- return ERR_PTR(-ENOMEM);
+ return NULL;
}
spin_lock_init(&sta->ampdu_mlme.ampdu_rx);
@@ -196,11 +205,27 @@ struct sta_info *sta_info_add(struct iee
}
skb_queue_head_init(&sta->ps_tx_buf);
skb_queue_head_init(&sta->tx_filtered);
+
+#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
+ printk(KERN_DEBUG "%s: Allocated STA %s\n",
+ wiphy_name(local->hw.wiphy), print_mac(mbuf, sta->addr));
+#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
+
+ return sta;
+}
+
+int sta_info_insert(struct sta_info *sta)
+{
+ struct ieee80211_local *local = sta->local;
+ struct ieee80211_sub_if_data *sdata = sta->sdata;
+ unsigned long flags;
+ DECLARE_MAC_BUF(mac);
+
spin_lock_irqsave(&local->sta_lock, flags);
/* check if STA exists already */
- if (__sta_info_find(local, addr)) {
+ if (__sta_info_find(local, sta->addr)) {
spin_unlock_irqrestore(&local->sta_lock, flags);
- return ERR_PTR(-EEXIST);
+ return -EEXIST;
}
list_add(&sta->list, &local->sta_list);
local->num_sta++;
@@ -212,16 +237,16 @@ struct sta_info *sta_info_add(struct iee
sdata = sdata->u.vlan.ap;
local->ops->sta_notify(local_to_hw(local), &sdata->vif,
- STA_NOTIFY_ADD, addr);
+ STA_NOTIFY_ADD, sta->addr);
}
- spin_unlock_irqrestore(&local->sta_lock, flags);
-
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
- printk(KERN_DEBUG "%s: Added STA %s\n",
- wiphy_name(local->hw.wiphy), print_mac(mac, addr));
+ printk(KERN_DEBUG "%s: Inserted STA %s\n",
+ wiphy_name(local->hw.wiphy), print_mac(mac, sta->addr));
#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
+ spin_unlock_irqrestore(&local->sta_lock, flags);
+
#ifdef CONFIG_MAC80211_DEBUGFS
/* debugfs entry adding might sleep, so schedule process
* context task for adding entry for STAs that do not yet
@@ -229,7 +254,7 @@ struct sta_info *sta_info_add(struct iee
queue_work(local->hw.workqueue, &local->sta_debugfs_add);
#endif
- return sta;
+ return 0;
}
static inline void __bss_tim_set(struct ieee80211_if_ap *bss, u16 aid)
--- everything.orig/net/mac80211/sta_info.h 2008-02-22 11:53:23.000000000 +0100
+++ everything/net/mac80211/sta_info.h 2008-02-22 11:54:34.000000000 +0100
@@ -248,12 +248,19 @@ struct sta_info {
*/
struct sta_info *sta_info_get(struct ieee80211_local *local, u8 *addr);
/*
- * Add a new STA info, must be under RCU read lock
- * because otherwise the returned reference isn't
- * necessarily valid long enough.
+ * Create a new STA info, caller owns returned structure
+ * until sta_info_insert().
*/
-struct sta_info *sta_info_add(struct ieee80211_sub_if_data *sdata,
- u8 *addr);
+struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
+ u8 *addr, gfp_t gfp);
+/*
+ * Insert STA info into hash table/list, returns zero or a
+ * -EEXIST if (if the same MAC address is already present).
+ *
+ * Calling this without RCU protection makes the caller
+ * relinquish its reference to @sta.
+ */
+int sta_info_insert(struct sta_info *sta);
/*
* Unlink a STA info from the hash table/list.
* This can NULL the STA pointer if somebody else
--- everything.orig/net/mac80211/cfg.c 2008-02-22 11:53:23.000000000 +0100
+++ everything/net/mac80211/cfg.c 2008-02-22 12:03:23.000000000 +0100
@@ -533,6 +533,12 @@ static void sta_apply_parameters(struct
int i, j;
struct ieee80211_supported_band *sband;
+ /*
+ * FIXME: updating the flags is racy when this function is
+ * called from ieee80211_change_station(), this will
+ * be resolved in a future patch.
+ */
+
if (params->station_flags & STATION_FLAG_CHANGED) {
sta->flags &= ~WLAN_STA_AUTHORIZED;
if (params->station_flags & STATION_FLAG_AUTHORIZED)
@@ -547,6 +553,13 @@ static void sta_apply_parameters(struct
sta->flags |= WLAN_STA_WME;
}
+ /*
+ * FIXME: updating the following information is racy when this
+ * function is called from ieee80211_change_station().
+ * However, all this information should be static so
+ * maybe we should just reject attemps to change it.
+ */
+
if (params->aid) {
sta->aid = params->aid;
if (sta->aid > IEEE80211_MAX_AID)
@@ -577,6 +590,7 @@ static int ieee80211_add_station(struct
struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
struct sta_info *sta;
struct ieee80211_sub_if_data *sdata;
+ int err;
/* Prevent a race with changing the rate control algorithm */
if (!netif_running(dev))
@@ -591,17 +605,9 @@ static int ieee80211_add_station(struct
} else
sdata = IEEE80211_DEV_TO_SUB_IF(dev);
- rcu_read_lock();
-
- sta = sta_info_add(sdata, mac);
- if (IS_ERR(sta)) {
- rcu_read_unlock();
- return PTR_ERR(sta);
- }
-
- if (sdata->vif.type == IEEE80211_IF_TYPE_VLAN ||
- sdata->vif.type == IEEE80211_IF_TYPE_AP)
- ieee80211_send_layer2_update(sta);
+ sta = sta_info_alloc(sdata, mac, GFP_KERNEL);
+ if (!sta)
+ return -ENOMEM;
sta->flags = WLAN_STA_AUTH | WLAN_STA_ASSOC;
@@ -609,7 +615,15 @@ static int ieee80211_add_station(struct
rate_control_rate_init(sta, local);
- rcu_read_unlock();
+ err = sta_info_insert(sta);
+ if (err) {
+ sta_info_destroy(sta);
+ return err;
+ }
+
+ if (sdata->vif.type == IEEE80211_IF_TYPE_VLAN ||
+ sdata->vif.type == IEEE80211_IF_TYPE_AP)
+ ieee80211_send_layer2_update(sta);
return 0;
}
--- everything.orig/net/mac80211/ieee80211.c 2008-02-22 11:53:23.000000000 +0100
+++ everything/net/mac80211/ieee80211.c 2008-02-22 11:54:34.000000000 +0100
@@ -888,6 +888,7 @@ int ieee80211_if_update_wds(struct net_d
struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
struct sta_info *sta;
+ int err;
DECLARE_MAC_BUF(mac);
might_sleep();
@@ -895,16 +896,19 @@ int ieee80211_if_update_wds(struct net_d
if (compare_ether_addr(remote_addr, sdata->u.wds.remote_addr) == 0)
return 0;
- rcu_read_lock();
-
/* Create STA entry for the new peer */
- sta = sta_info_add(sdata, remote_addr);
- if (IS_ERR(sta)) {
- rcu_read_unlock();
- return PTR_ERR(sta);
- }
+ sta = sta_info_alloc(sdata, remote_addr, GFP_KERNEL);
+ if (!sta)
+ return -ENOMEM;
sta->flags |= WLAN_STA_AUTHORIZED;
+ err = sta_info_insert(sta);
+ if (err) {
+ sta_info_destroy(sta);
+ return err;
+ }
+
+ rcu_read_lock();
/* Remove STA entry for the old peer */
sta = sta_info_get(local, sdata->u.wds.remote_addr);
--- everything.orig/net/mac80211/ieee80211_sta.c 2008-02-22 11:53:23.000000000 +0100
+++ everything/net/mac80211/ieee80211_sta.c 2008-02-22 11:56:41.000000000 +0100
@@ -1461,7 +1461,7 @@ void sta_addba_resp_timer_expired(unsign
{
/* not an elegant detour, but there is no choice as the timer passes
* only one argument, and both sta_info and TID are needed, so init
- * flow in sta_info_add gives the TID as data, while the timer_to_id
+ * flow in sta_info_create gives the TID as data, while the timer_to_id
* array gives the sta through container_of */
u16 tid = *(int *)data;
struct sta_info *temp_sta = container_of((void *)data,
@@ -1512,7 +1512,7 @@ void sta_rx_agg_session_timer_expired(un
{
/* not an elegant detour, but there is no choice as the timer passes
* only one argument, and verious sta_info are needed here, so init
- * flow in sta_info_add gives the TID as data, while the timer_to_id
+ * flow in sta_info_create gives the TID as data, while the timer_to_id
* array gives the sta through container_of */
u8 *ptid = (u8 *)data;
u8 *timer_to_id = ptid - *ptid;
@@ -1836,11 +1836,12 @@ static void ieee80211_rx_mgmt_assoc_resp
sta = sta_info_get(local, ifsta->bssid);
if (!sta) {
struct ieee80211_sta_bss *bss;
+ int err;
- sta = sta_info_add(sdata, ifsta->bssid);
- if (IS_ERR(sta)) {
- printk(KERN_DEBUG "%s: failed to add STA entry for the"
- " AP (error %ld)\n", dev->name, PTR_ERR(sta));
+ sta = sta_info_alloc(sdata, ifsta->bssid, GFP_ATOMIC);
+ if (!sta) {
+ printk(KERN_DEBUG "%s: failed to alloc STA entry for"
+ " the AP\n", dev->name);
rcu_read_unlock();
return;
}
@@ -1853,8 +1854,27 @@ static void ieee80211_rx_mgmt_assoc_resp
sta->last_noise = bss->noise;
ieee80211_rx_bss_put(dev, bss);
}
+
+ err = sta_info_insert(sta);
+ if (err) {
+ printk(KERN_DEBUG "%s: failed to insert STA entry for"
+ " the AP (error %d)\n", dev->name, err);
+ sta_info_destroy(sta);
+ rcu_read_unlock();
+ return;
+ }
}
+ /*
+ * FIXME: Do we really need to update the sta_info's information here?
+ * We already know about the AP (we found it in our list) so it
+ * should already be filled with the right info, no?
+ * As is stands, all this is racy because typically we assume
+ * the information that is filled in here (except flags) doesn't
+ * change while a STA structure is alive. As such, it should move
+ * to between the sta_info_alloc() and sta_info_insert() above.
+ */
+
sta->flags |= WLAN_STA_AUTH | WLAN_STA_ASSOC | WLAN_STA_ASSOC_AP |
WLAN_STA_AUTHORIZED;
@@ -2494,10 +2514,8 @@ static void ieee80211_rx_bss_info(struct
"local TSF - IBSS merge with BSSID %s\n",
dev->name, print_mac(mac, mgmt->bssid));
ieee80211_sta_join_ibss(dev, &sdata->u.sta, bss);
- rcu_read_lock();
ieee80211_ibss_add_sta(dev, NULL,
mgmt->bssid, mgmt->sa);
- rcu_read_unlock();
}
}
@@ -3837,7 +3855,6 @@ int ieee80211_sta_set_extra_ie(struct ne
}
-/* must be called under RCU read lock */
struct sta_info * ieee80211_ibss_add_sta(struct net_device *dev,
struct sk_buff *skb, u8 *bssid,
u8 *addr)
@@ -3860,8 +3877,8 @@ struct sta_info * ieee80211_ibss_add_sta
printk(KERN_DEBUG "%s: Adding new IBSS station %s (dev=%s)\n",
wiphy_name(local->hw.wiphy), print_mac(mac, addr), dev->name);
- sta = sta_info_add(sdata, addr);
- if (IS_ERR(sta))
+ sta = sta_info_alloc(sdata, addr, GFP_ATOMIC);
+ if (!sta)
return NULL;
sta->flags |= WLAN_STA_AUTHORIZED;
@@ -3871,6 +3888,11 @@ struct sta_info * ieee80211_ibss_add_sta
rate_control_rate_init(sta, local);
+ if (sta_info_insert(sta)) {
+ sta_info_destroy(sta);
+ return NULL;
+ }
+
return sta;
}
--
-
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