iwlegacy: fix BUG_ON(info->control.rates[0].idx < 0)

commit 7c2510120e9b43b0caf32c3786a6ab831f7d9e87 upstream.

When trying to connect to 5GHz we can provide negative index to
mac80211 what trigger BUG_ON. Reason of iwl-3945-rs malfunction
on 5GHz is unknown and needs further investigation. For now, to
do not trigger a bug, correct value and just print WARNING.

Address bug:
https://bugzilla.redhat.com/show_bug.cgi?id=730653

Reported-and-tested-by: Jan Teichmann <jan.teichmann@gmail.com>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/net/wireless/iwlegacy/iwl-3945-rs.c b/drivers/net/wireless/iwlegacy/iwl-3945-rs.c
index 977bd24..164bcae 100644 (file)
--- a/drivers/net/wireless/iwlegacy/iwl-3945-rs.c
+++ b/drivers/net/wireless/iwlegacy/iwl-3945-rs.c
@@ -822,12 +822,15 @@ static void iwl3945_rs_get_rate(void *priv_r, struct ieee80211_sta *sta,
 
  out:
 
-       rs_sta->last_txrate_idx = index;
-       if (sband->band == IEEE80211_BAND_5GHZ)
-               info->control.rates[0].idx = rs_sta->last_txrate_idx -
-                               IWL_FIRST_OFDM_RATE;
-       else
+       if (sband->band == IEEE80211_BAND_5GHZ) {
+               if (WARN_ON_ONCE(index < IWL_FIRST_OFDM_RATE))
+                       index = IWL_FIRST_OFDM_RATE;
+               rs_sta->last_txrate_idx = index;
+               info->control.rates[0].idx = index - IWL_FIRST_OFDM_RATE;
+       } else {
+               rs_sta->last_txrate_idx = index;
                info->control.rates[0].idx = rs_sta->last_txrate_idx;
+       }
 
        IWL_DEBUG_RATE(priv, "leave: %d\n", index);
 }