mac80211: fix tid_agg_rx NULL dereference

commit 1c3d185a9a0b136a58e73b02912d593d0303d1da upstream.

On drivers setting the SUPPORTS_REORDERING_BUFFER hardware flag,
we crash when the peer sends an AddBA request while we already
have a session open on the seame TID; this is because on those
drivers, the tid_agg_rx is left NULL even though the session is
valid, and the agg_session_valid bit is set.

To fix this, store the dialog tokens outside the tid_agg_rx to
be able to compare them to the received AddBA request.

Fixes: f89e07d4cf26 ("mac80211: agg-rx: refuse ADDBA Request with timeout update")
Reported-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index ed5fcb9..dd06ef0 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -184,7 +184,6 @@
  * @ssn: Starting Sequence Number expected to be aggregated.
  * @buf_size: buffer size for incoming A-MPDUs
  * @timeout: reset timer value (in TUs).
- * @dialog_token: dialog token for aggregation session
  * @rcu_head: RCU head used for freeing this struct
  * @reorder_lock: serializes access to reorder buffer, see below.
  * @auto_seq: used for offloaded BA sessions to automatically pick head_seq_and
@@ -213,7 +212,6 @@
 	u16 ssn;
 	u16 buf_size;
 	u16 timeout;
-	u8 dialog_token;
 	bool auto_seq;
 	bool removed;
 };
@@ -225,6 +223,7 @@
  *	to tid_tx[idx], which are protected by the sta spinlock)
  *	tid_start_tx is also protected by sta->lock.
  * @tid_rx: aggregation info for Rx per TID -- RCU protected
+ * @tid_rx_token: dialog tokens for valid aggregation sessions
  * @tid_rx_timer_expired: bitmap indicating on which TIDs the
  *	RX timer expired until the work for it runs
  * @tid_rx_stop_requested:  bitmap indicating which BA sessions per TID the
@@ -243,6 +242,7 @@
 	struct mutex mtx;
 	/* rx */
 	struct tid_ampdu_rx __rcu *tid_rx[IEEE80211_NUM_TIDS];
+	u8 tid_rx_token[IEEE80211_NUM_TIDS];
 	unsigned long tid_rx_timer_expired[BITS_TO_LONGS(IEEE80211_NUM_TIDS)];
 	unsigned long tid_rx_stop_requested[BITS_TO_LONGS(IEEE80211_NUM_TIDS)];
 	unsigned long agg_session_valid[BITS_TO_LONGS(IEEE80211_NUM_TIDS)];