mac80211: make sure data is accessible in EAPOL check

The code to allow EAPOL frames even when the station
isn't yet marked associated needs to check that the
incoming frame is long enough and due to paged RX it
also can't assume skb->data contains the right data,
it must use skb_copy_bits(). Fix this to avoid using
data that doesn't really exist.

Cc: stable@vger.kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 265a032dec499128156efa85c9a9cdd78b730bfe..00ade7feb2e3a3b84af12be5bfad378bd8907182 100644 (file)
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -888,14 +888,16 @@ ieee80211_rx_h_check(struct ieee80211_rx_data *rx)
                 */
                if (rx->sta && rx->sdata->vif.type == NL80211_IFTYPE_STATION &&
                    ieee80211_is_data_present(hdr->frame_control)) {
-                       u16 ethertype;
-                       u8 *payload;
-
-                       payload = rx->skb->data +
-                               ieee80211_hdrlen(hdr->frame_control);
-                       ethertype = (payload[6] << 8) | payload[7];
-                       if (cpu_to_be16(ethertype) ==
-                           rx->sdata->control_port_protocol)
+                       unsigned int hdrlen;
+                       __be16 ethertype;
+
+                       hdrlen = ieee80211_hdrlen(hdr->frame_control);
+
+                       if (rx->skb->len < hdrlen + 8)
+                               return RX_DROP_MONITOR;
+
+                       skb_copy_bits(rx->skb, hdrlen + 6, &ethertype, 2);
+                       if (ethertype == rx->sdata->control_port_protocol)
                                return RX_CONTINUE;
                }