[PATCH 3.2 042/126] mac80211: discard multicast and 4-addr A-MSDUs

Ben Hutchings
2017-02-15T23:04:13Z

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

commit ea720935cf6686f72def9d322298bf7e9bd53377 upstream.

In mac80211, multicast A-MSDUs are accepted in many cases that
they shouldn't be accepted in:
* drop A-MSDUs with a multicast A1 (RA), as required by the
spec in 9.11 (802.11-2012 version)
* drop A-MSDUs with a 4-addr header, since the fourth address
can't actually be useful for them; unless 4-address frame
format is actually requested, even though the fourth address
is still not useful in this case, but ignored

Accepting the first case, in particular, is very problematic
since it allows anyone else with possession of a GTK to send
unicast frames encapsulated in a multicast A-MSDU, even when
the AP has client isolation enabled.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/mac80211/rx.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)

--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1854,16 +1854,22 @@ ieee80211_rx_h_amsdu(struct ieee80211_rx
if (!(status->rx_flags & IEEE80211_RX_AMSDU))
return RX_CONTINUE;

- if (ieee80211_has_a4(hdr->frame_control) &&
- rx->sdata->vif.type == NL80211_IFTYPE_AP_VLAN &&
- !rx->sdata->u.vlan.sta)
- return RX_DROP_UNUSABLE;
+ if (unlikely(ieee80211_has_a4(hdr->frame_control))) {
+ switch (rx->sdata->vif.type) {
+ case NL80211_IFTYPE_AP_VLAN:
+ if (!rx->sdata->u.vlan.sta)
+ return RX_DROP_UNUSABLE;
+ break;
+ case NL80211_IFTYPE_STATION:
+ if (!rx->sdata->u.mgd.use_4addr)
+ return RX_DROP_UNUSABLE;
+ break;
+ default:
+ return RX_DROP_UNUSABLE;
+ }
+ }

- if (is_multicast_ether_addr(hdr->addr1) &&
- ((rx->sdata->vif.type == NL80211_IFTYPE_AP_VLAN &&
- rx->sdata->u.vlan.sta) ||
- (rx->sdata->vif.type == NL80211_IFTYPE_STATION &&
- rx->sdata->u.mgd.use_4addr)))
+ if (is_multicast_ether_addr(hdr->addr1))
return RX_DROP_UNUSABLE;

skb->dev = dev;