Kernel panic in ieee80211_calculate_rx_timestamp

[Thomas Lindroth <thomas.lindroth@gmail.com>]

I recently got a ath9k_htc based dongle and running kismet for a few
hours results in a kernel panic (divide error) in
ieee80211_calculate_rx_timestamp with kernel 3.11.0.

The problem seems to occur when the call to cfg80211_calculate_bitrate
returns 0. I've used this patch to temporarily works around the problem.

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 2265445..037b737 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -2156,6 +2156,9 @@ u64 ieee80211_calculate_rx_timestamp(struct
ieee80211_local *local,

        rate = cfg80211_calculate_bitrate(&ri);

+       if (WARN_ON(!rate))
+               return 0;
+
        /* rewind from end of MPDU */
        if (status->flag & RX_FLAG_MACTIME_END)
                ts -= mpdu_len * 8 * 10 / rate;


http://i.imgur.com/BrpaCgI.jpg here is the output of the panic.

/Thomas Lindroth