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mac80211: fix rcu-unsafe pointer dereference

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This patch fixes a potential crash (null-pointer de-
reference) which was introduced in my previous patch:
 "mac80211: AMPDU rx reorder timeout timer"

During a BA teardown, the pointer to the soon-to-be-gone
tid_ampdu_rx element will be nullified. Therefore the
release timer mechanism has to be careful not to
accidentally access the item without any RCU protection.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Christian Lamparter 2010-08-24 19:22:42 +02:00 committed by John W. Linville
parent 74b70a4e38
commit 2c15a0cf27
1 changed files with 8 additions and 4 deletions
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12
net/mac80211/rx.c
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@ -2479,6 +2479,11 @@ void ieee80211_release_reorder_timeout(struct sta_info *sta, int tid)
{
struct sk_buff_head frames;
struct ieee80211_rx_data rx = { };
struct tid_ampdu_rx *tid_agg_rx;
tid_agg_rx = rcu_dereference(sta->ampdu_mlme.tid_rx[tid]);
if (!tid_agg_rx)
return;
__skb_queue_head_init(&frames);
@ -2493,10 +2498,9 @@ void ieee80211_release_reorder_timeout(struct sta_info *sta, int tid)
test_bit(SCAN_OFF_CHANNEL, &sta->local->scanning)))
rx.flags |= IEEE80211_RX_IN_SCAN;
spin_lock(&sta->ampdu_mlme.tid_rx[tid]->reorder_lock);
ieee80211_sta_reorder_release(&sta->local->hw,
sta->ampdu_mlme.tid_rx[tid], &frames);
spin_unlock(&sta->ampdu_mlme.tid_rx[tid]->reorder_lock);
spin_lock(&tid_agg_rx->reorder_lock);
ieee80211_sta_reorder_release(&sta->local->hw, tid_agg_rx, &frames);
spin_unlock(&tid_agg_rx->reorder_lock);
ieee80211_rx_handlers(&rx, &frames);
}