mac80211: fix max HT rate processing on mac80211

The max MCS index is 76, fix the higher check to allow through
frames received at MCS 76. This is a non-issue for current drivers
as MCS 76 is only possible with a device supporting 4 spatial
streams.

While at it change the WARN_ON() on invalid HT rates to a WARN()
to provide more useful information. This will help debug issues
when the driver is passing up a bogus HT rate value.

The rate must map to a valid MCS index which can be any of the
values in the set [0 - 76] (inclusive).

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 15 insertions, 3 deletions

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 76478362a538..006cf89df70b 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -2441,9 +2441,21 @@ void ieee80211_rx(struct ieee80211_hw *hw, struct sk_buff *skb)
                 goto drop;
 
         if (status->flag & RX_FLAG_HT) {
-                /* rate_idx is MCS index */
-                if (WARN_ON(status->rate_idx < 0 ||
-                            status->rate_idx >= 76))
+                /*
+                 * rate_idx is MCS index, which can be [0-76] as documented on:
+                 *
+                 * http://wireless.kernel.org/en/developers/Documentation/ieee80211/802.11n
+                 *
+                 * Anything else would be some sort of driver or hardware error.
+                 * The driver should catch hardware errors.
+                 */
+                if (WARN((status->rate_idx < 0 ||
+                         status->rate_idx > 76),
+                         "Rate marked as an HT rate but passed "
+                         "status->rate_idx is not "
+                         "an MCS index [0-76]: %d (0x%02x)\n",
+                         status->rate_idx,
+                         status->rate_idx))
                         goto drop;
                 /* HT rates are not in the table - use the highest legacy rate
                  * for now since other parts of mac80211 may not yet be fully