cfg80211: fix BSS double-unlinking (continued)

This patch adds to the fix "fix BSS double-unlinking"
(commit 3207390a8b58bfc1335750f91cf6783c48ca19ca) by Johannes Berg.

It turns out, that the double-unlinking scenario can also occur if expired
BSS elements are removed whilst an interface is performing association.

To work around that, replace list_del with list_del_init also in the
"cfg80211_bss_expire" function, so that the check for whether the BSS still is
in the list works correctly in cfg80211_unlink_bss.

Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 11 insertions, 7 deletions

diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index 300c11d99997..fbf6f33ae4d0 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -124,6 +124,15 @@ void cfg80211_bss_age(struct cfg80211_registered_device *dev,
 }
 
 /* must hold dev->bss_lock! */
+static void __cfg80211_unlink_bss(struct cfg80211_registered_device *dev,
+                                  struct cfg80211_internal_bss *bss)
+{
+        list_del_init(&bss->list);
+        rb_erase(&bss->rbn, &dev->bss_tree);
+        kref_put(&bss->ref, bss_release);
+}
+
+/* must hold dev->bss_lock! */
 void cfg80211_bss_expire(struct cfg80211_registered_device *dev)
 {
         struct cfg80211_internal_bss *bss, *tmp;
@@ -134,9 +143,7 @@ void cfg80211_bss_expire(struct cfg80211_registered_device *dev)
                         continue;
                 if (!time_after(jiffies, bss->ts + IEEE80211_SCAN_RESULT_EXPIRE))
                         continue;
-                list_del(&bss->list);
-                rb_erase(&bss->rbn, &dev->bss_tree);
-                kref_put(&bss->ref, bss_release);
+                __cfg80211_unlink_bss(dev, bss);
                 expired = true;
         }
 
@@ -669,11 +676,8 @@ void cfg80211_unlink_bss(struct wiphy *wiphy, struct cfg80211_bss *pub)
 
         spin_lock_bh(&dev->bss_lock);
         if (!list_empty(&bss->list)) {
-                list_del_init(&bss->list);
+                __cfg80211_unlink_bss(dev, bss);
                 dev->bss_generation++;
-                rb_erase(&bss->rbn, &dev->bss_tree);
-
-                kref_put(&bss->ref, bss_release);
         }
         spin_unlock_bh(&dev->bss_lock);
 }