mac80211: delay skb linearising in rx decryption

We delay the skb linearising in ieee80211_rx_h_decrypt so that
frames do not require software decryption are not linearized. We
are safe to do this because ieee80211_get_mmie_keyidx() only
requires to touch nonlinear data for management frames, which are
already linearized before getting here.

Cc: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 9 insertions, 7 deletions

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index d08ede44ac7..8ee7db19326 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -820,7 +820,7 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
 {
         struct sk_buff *skb = rx->skb;
         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
-        struct ieee80211_hdr *hdr;
+        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
         int keyidx;
         int hdrlen;
         ieee80211_rx_result result = RX_DROP_UNUSABLE;
@@ -861,11 +861,6 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
         if (!(rx->flags & IEEE80211_RX_RA_MATCH))
                 return RX_CONTINUE;
 
-        if (skb_linearize(rx->skb))
-                return RX_DROP_UNUSABLE;
-
-        hdr = (struct ieee80211_hdr *)skb->data;
-
         /* start without a key */
         rx->key = NULL;
 
@@ -906,6 +901,7 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
                         rx->key = key;
                 return RX_CONTINUE;
         } else {
+                u8 keyid;
                 /*
                  * The device doesn't give us the IV so we won't be
                  * able to look up the key. That's ok though, we
@@ -928,7 +924,8 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
                  * no need to call ieee80211_wep_get_keyidx,
                  * it verifies a bunch of things we've done already
                  */
-                keyidx = rx->skb->data[hdrlen + 3] >> 6;
+                skb_copy_bits(rx->skb, hdrlen + 3, &keyid, 1);
+                keyidx = keyid >> 6;
 
                 rx->key = rcu_dereference(rx->sdata->keys[keyidx]);
 
@@ -949,6 +946,11 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
                 return RX_DROP_MONITOR;
         }
 
+        if (skb_linearize(rx->skb))
+                return RX_DROP_UNUSABLE;
+
+        hdr = (struct ieee80211_hdr *)rx->skb->data;
+
         /* Check for weak IVs if possible */
         if (rx->sta && rx->key->conf.alg == ALG_WEP &&
             ieee80211_is_data(hdr->frame_control) &&