package/mac80211/patches/407-debugfs-sta-work-fix.patch

   1 Subject: mac80211: fix debugfs lockup
   2
   3 When debugfs_create_dir fails, sta_info_debugfs_add_work will not
   4 terminate because it will find the same station again and again.
   5 This is possible whenever debugfs fails for whatever reason; one
   6 reason is a race condition in mac80211, unfortunately we cannot
   7 do much about it, so just document it, it just means some station
   8 may be missing from debugfs.
   9
  10 Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
  11 Cc: Robin Holt <holt@sgi.com>
  12 ---
  13  net/mac80211/debugfs_sta.c |   11 +++++++++++
  14  net/mac80211/sta_info.c    |    7 ++++++-
  15  net/mac80211/sta_info.h    |    1 +
  16  3 files changed, 18 insertions(+), 1 deletion(-)
  17
  18 --- everything.orig/net/mac80211/debugfs_sta.c  2008-10-07 20:05:29.000000000 +0200
  19 +++ everything/net/mac80211/debugfs_sta.c       2008-10-07 20:06:39.000000000 +0200
  20 @@ -249,11 +249,22 @@ void ieee80211_sta_debugfs_add(struct st
  21         DECLARE_MAC_BUF(mbuf);
  22         u8 *mac;
  23
  24 +       sta->debugfs.add_has_run = true;
  25 +
  26         if (!stations_dir)
  27                 return;
  28
  29         mac = print_mac(mbuf, sta->sta.addr);
  30
  31 +       /*
  32 +        * This might fail due to a race condition:
  33 +        * When mac80211 unlinks a station, the debugfs entries
  34 +        * remain, but it is already possible to link a new
  35 +        * station with the same address which triggers adding
  36 +        * it to debugfs; therefore, if the old station isn't
  37 +        * destroyed quickly enough the old station's debugfs
  38 +        * dir might still be around.
  39 +        */
  40         sta->debugfs.dir = debugfs_create_dir(mac, stations_dir);
  41         if (!sta->debugfs.dir)
  42                 return;
  43 --- everything.orig/net/mac80211/sta_info.c     2008-10-07 20:05:29.000000000 +0200
  44 +++ everything/net/mac80211/sta_info.c  2008-10-07 20:06:39.000000000 +0200
  45 @@ -635,7 +635,12 @@ static void sta_info_debugfs_add_work(st
  46
  47                 spin_lock_irqsave(&local->sta_lock, flags);
  48                 list_for_each_entry(tmp, &local->sta_list, list) {
  49 -                       if (!tmp->debugfs.dir) {
  50 +                       /*
  51 +                        * debugfs.add_has_run will be set by
  52 +                        * ieee80211_sta_debugfs_add regardless
  53 +                        * of what else it does.
  54 +                        */
  55 +                       if (!tmp->debugfs.add_has_run) {
  56                                 sta = tmp;
  57                                 __sta_info_pin(sta);
  58                                 break;
  59 --- everything.orig/net/mac80211/sta_info.h     2008-10-07 20:05:29.000000000 +0200
  60 +++ everything/net/mac80211/sta_info.h  2008-10-07 20:06:39.000000000 +0200
  61 @@ -300,6 +300,7 @@ struct sta_info {
  62                 struct dentry *inactive_ms;
  63                 struct dentry *last_seq_ctrl;
  64                 struct dentry *agg_status;
  65 +               bool add_has_run;
  66         } debugfs;
  67  #endif
  68