mac80211: minstrel: avoid accessing negative indices in rix_to_ndx()

If rix is not found in mi->r[], i will become -1 after the loop.  This value
is eventually used to access arrays, so we were accessing arrays with a
negative index, which is obviously not what we want to do.  This patch fixes
this potential problem.

Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Acked-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
index b218b98fba7f..37771abd8f5a 100644
--- a/net/mac80211/rc80211_minstrel.c
+++ b/net/mac80211/rc80211_minstrel.c
@@ -66,7 +66,7 @@ rix_to_ndx(struct minstrel_sta_info *mi, int rix)
         for (i = rix; i >= 0; i--)
                 if (mi->r[i].rix == rix)
                         break;
-        WARN_ON(mi->r[i].rix != rix);
+        WARN_ON(i < 0);
         return i;
 }
 
@@ -181,6 +181,9 @@ minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
                         break;
 
                 ndx = rix_to_ndx(mi, ar[i].idx);
+                if (ndx < 0)
+                        continue;
+
                 mi->r[ndx].attempts += ar[i].count;
 
                 if ((i != IEEE80211_TX_MAX_RATES - 1) && (ar[i + 1].idx < 0))