[ 15/42] mac80211: fix possible tid_rx->reorder_timer use after free

From: Greg KH
Date: Wed Apr 11 2012 - 19:28:23 EST


3.0-stable review patch. If anyone has any objections, please let me know.

------------------

From: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>

commit d72308bff5c2fa207949a5925b020bce74495e33 upstream.

Is possible that we will arm the tid_rx->reorder_timer after
del_timer_sync() in ___ieee80211_stop_rx_ba_session(). We need to stop
timer after RCU grace period finish, so move it to
ieee80211_free_tid_rx(). Timer will not be armed again, as
rcu_dereference(sta->ampdu_mlme.tid_rx[tid]) will return NULL.

Debug object detected problem with the following warning:
ODEBUG: free active (active state 0) object type: timer_list hint: sta_rx_agg_reorder_timer_expired+0x0/0xf0 [mac80211]

Bug report (with all warning messages):
https://bugzilla.redhat.com/show_bug.cgi?id=804007

Reported-by: "jan p. springer" <jsd@xxxxxxxxxx>
Signed-off-by: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
Signed-off-by: John W. Linville <linville@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
net/mac80211/agg-rx.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/mac80211/agg-rx.c
+++ b/net/mac80211/agg-rx.c
@@ -48,6 +48,8 @@ static void ieee80211_free_tid_rx(struct
container_of(h, struct tid_ampdu_rx, rcu_head);
int i;

+ del_timer_sync(&tid_rx->reorder_timer);
+
for (i = 0; i < tid_rx->buf_size; i++)
dev_kfree_skb(tid_rx->reorder_buf[i]);
kfree(tid_rx->reorder_buf);
@@ -87,7 +89,6 @@ void ___ieee80211_stop_rx_ba_session(str
tid, 0, reason);

del_timer_sync(&tid_rx->session_timer);
- del_timer_sync(&tid_rx->reorder_timer);

call_rcu(&tid_rx->rcu_head, ieee80211_free_tid_rx);
}


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