p54: fix oops on faulty devices

This patch fixes an oops when the devices suddenly starts
to receive martian data frames.

bug reference:
http://marc.info/?l=linux-wireless&m=122872280317635&w=2

Signed-off-by: Christian Lamparter <chunkeey@web.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 16 insertions, 3 deletions

diff --git a/drivers/net/wireless/p54/p54common.c b/drivers/net/wireless/p54/p54common.c
index fac6b416e9e9..a4e99b02af02 100644
--- a/drivers/net/wireless/p54/p54common.c
+++ b/drivers/net/wireless/p54/p54common.c
@@ -540,6 +540,14 @@ static int p54_rx_data(struct ieee80211_hw *dev, struct sk_buff *skb)
         size_t header_len = sizeof(*hdr);
         u32 tsf32;
 
+        /*
+         * If the device is in a unspecified state we have to
+         * ignore all data frames. Else we could end up with a
+         * nasty crash.
+         */
+        if (unlikely(priv->mode == NL80211_IFTYPE_UNSPECIFIED))
+                return 0;
+
         if (!(hdr->flags & cpu_to_le16(P54_HDR_FLAG_DATA_IN_FCS_GOOD))) {
                 if (priv->filter_flags & FIF_FCSFAIL)
                         rx_status.flag |= RX_FLAG_FAILED_FCS_CRC;
@@ -608,6 +616,12 @@ void p54_free_skb(struct ieee80211_hw *dev, struct sk_buff *skb)
         if (unlikely(!skb || !dev || !skb_queue_len(&priv->tx_queue)))
                 return;
 
+        /*
+         * don't try to free an already unlinked skb
+         */
+        if (unlikely((!skb->next) || (!skb->prev)))
+                return;
+
         spin_lock_irqsave(&priv->tx_queue.lock, flags);
         info = IEEE80211_SKB_CB(skb);
         range = (void *)info->rate_driver_data;
@@ -1695,19 +1709,18 @@ static void p54_stop(struct ieee80211_hw *dev)
         struct sk_buff *skb;
 
         mutex_lock(&priv->conf_mutex);
+        priv->mode = NL80211_IFTYPE_UNSPECIFIED;
         del_timer(&priv->stats_timer);
         p54_free_skb(dev, priv->cached_stats);
         priv->cached_stats = NULL;
         if (priv->cached_beacon)
                 p54_tx_cancel(dev, priv->cached_beacon);
 
+        priv->stop(dev);
         while ((skb = skb_dequeue(&priv->tx_queue)))
                 kfree_skb(skb);
-
         priv->cached_beacon = NULL;
-        priv->stop(dev);
         priv->tsf_high32 = priv->tsf_low32 = 0;
-        priv->mode = NL80211_IFTYPE_UNSPECIFIED;
         mutex_unlock(&priv->conf_mutex);
 }