[PATCH 4.9 16/21] mac80211: fix MU-MIMO follow-MAC mode

Greg Kroah-Hartman
2017-04-25T15:29:06Z

From: Johannes Berg <johannes.berg@intel.com>

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>

---
net/mac80211/rx.c | 65 +++++++++++++++++++++++++++++++++++++++---------------
1 file changed, 47 insertions(+), 18 deletions(-)

--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -208,6 +208,51 @@ ieee80211_rx_radiotap_hdrlen(struct ieee
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_lo
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_lo
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_lo
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);