mac80211: fix MU-MIMO follow-MAC mode

commit 9e478066eae41211c92a8f63cc69aafc391bd6ab upstream.

There are two bugs in the follow-MAC code:
 * it treats the radiotap header as the 802.11 header
   (therefore it can't possibly work)
 * it doesn't verify that the skb data it accesses is actually
   present in the header, which is mitigated by the first point

Fix this by moving all of this out into a separate function.
This function copies the data it needs using skb_copy_bits()
to make sure it can be accessed if it's paged, and offsets
that by the possibly present vendor radiotap header.

This also makes all those conditions more readable.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 47 insertions, 18 deletions

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index e2bbad0e494c..acaaf616da71 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -208,6 +208,51 @@ ieee80211_rx_radiotap_hdrlen(struct ieee80211_local *local,
         return len;
 }
 
+static void ieee80211_handle_mu_mimo_mon(struct ieee80211_sub_if_data *sdata,
+                                         struct sk_buff *skb,
+                                         int rtap_vendor_space)
+{
+        struct {
+                struct ieee80211_hdr_3addr hdr;
+                u8 category;
+                u8 action_code;
+        } __packed action;
+
+        if (!sdata)
+                return;
+
+        BUILD_BUG_ON(sizeof(action) != IEEE80211_MIN_ACTION_SIZE + 1);
+
+        if (skb->len < rtap_vendor_space + sizeof(action) +
+                       VHT_MUMIMO_GROUPS_DATA_LEN)
+                return;
+
+        if (!is_valid_ether_addr(sdata->u.mntr.mu_follow_addr))
+                return;
+
+        skb_copy_bits(skb, rtap_vendor_space, &action, sizeof(action));
+
+        if (!ieee80211_is_action(action.hdr.frame_control))
+                return;
+
+        if (action.category != WLAN_CATEGORY_VHT)
+                return;
+
+        if (action.action_code != WLAN_VHT_ACTION_GROUPID_MGMT)
+                return;
+
+        if (!ether_addr_equal(action.hdr.addr1, sdata->u.mntr.mu_follow_addr))
+                return;
+
+        skb = skb_copy(skb, GFP_ATOMIC);
+        if (!skb)
+                return;
+
+        skb->pkt_type = IEEE80211_SDATA_QUEUE_TYPE_FRAME;
+        skb_queue_tail(&sdata->skb_queue, skb);
+        ieee80211_queue_work(&sdata->local->hw, &sdata->work);
+}
+
 /*
  * ieee80211_add_rx_radiotap_header - add radiotap header
  *
@@ -515,7 +560,6 @@ ieee80211_rx_monitor(struct ieee80211_local *local, struct sk_buff *origskb,
         struct net_device *prev_dev = NULL;
         int present_fcs_len = 0;
         unsigned int rtap_vendor_space = 0;
-        struct ieee80211_mgmt *mgmt;
         struct ieee80211_sub_if_data *monitor_sdata =
                 rcu_dereference(local->monitor_sdata);
 
@@ -553,6 +597,8 @@ ieee80211_rx_monitor(struct ieee80211_local *local, struct sk_buff *origskb,
                 return remove_monitor_info(local, origskb, rtap_vendor_space);
         }
 
+        ieee80211_handle_mu_mimo_mon(monitor_sdata, origskb, rtap_vendor_space);
+
         /* room for the radiotap header based on driver features */
         rt_hdrlen = ieee80211_rx_radiotap_hdrlen(local, status, origskb);
         needed_headroom = rt_hdrlen - rtap_vendor_space;
@@ -618,23 +664,6 @@ ieee80211_rx_monitor(struct ieee80211_local *local, struct sk_buff *origskb,
                 ieee80211_rx_stats(sdata->dev, skb->len);
         }
 
-        mgmt = (void *)skb->data;
-        if (monitor_sdata &&
-            skb->len >= IEEE80211_MIN_ACTION_SIZE + 1 + VHT_MUMIMO_GROUPS_DATA_LEN &&
-            ieee80211_is_action(mgmt->frame_control) &&
-            mgmt->u.action.category == WLAN_CATEGORY_VHT &&
-            mgmt->u.action.u.vht_group_notif.action_code == WLAN_VHT_ACTION_GROUPID_MGMT &&
-            is_valid_ether_addr(monitor_sdata->u.mntr.mu_follow_addr) &&
-            ether_addr_equal(mgmt->da, monitor_sdata->u.mntr.mu_follow_addr)) {
-                struct sk_buff *mu_skb = skb_copy(skb, GFP_ATOMIC);
-
-                if (mu_skb) {
-                        mu_skb->pkt_type = IEEE80211_SDATA_QUEUE_TYPE_FRAME;
-                        skb_queue_tail(&monitor_sdata->skb_queue, mu_skb);
-                        ieee80211_queue_work(&local->hw, &monitor_sdata->work);
-                }
-        }
-
         if (prev_dev) {
                 skb->dev = prev_dev;
                 netif_receive_skb(skb);