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/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;