From f68391eb9bfd80cc898b07e71ed400d7e0c0f91a Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Wed, 1 Apr 2015 14:20:42 +0200 Subject: mac80211: fix RX A-MPDU session reorder timer deletion [ Upstream commit 788211d81bfdf9b6a547d0530f206ba6ee76b107 ] There's an issue with the way the RX A-MPDU reorder timer is deleted that can cause a kernel crash like this: * tid_rx is removed - call_rcu(ieee80211_free_tid_rx) * station is destroyed * reorder timer fires before ieee80211_free_tid_rx() runs, accessing the station, thus potentially crashing due to the use-after-free The station deletion is protected by synchronize_net(), but that isn't enough -- ieee80211_free_tid_rx() need not have run when that returns (it deletes the timer.) We could use rcu_barrier() instead of synchronize_net(), but that's much more expensive. Instead, to fix this, add a field tracking that the session is being deleted. In this case, the only re-arming of the timer happens with the reorder spinlock held, so make that code not rearm it if the session is being deleted and also delete the timer after setting that field. This ensures the timer cannot fire after ___ieee80211_stop_rx_ba_session() returns, which fixes the problem. Cc: stable@vger.kernel.org Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin --- net/mac80211/agg-rx.c | 8 ++++++-- net/mac80211/rx.c | 7 ++++--- net/mac80211/sta_info.h | 2 ++ 3 files changed, 12 insertions(+), 5 deletions(-) diff --git a/net/mac80211/agg-rx.c b/net/mac80211/agg-rx.c index a48bad468880..7702978a4c99 100644 --- a/net/mac80211/agg-rx.c +++ b/net/mac80211/agg-rx.c @@ -49,8 +49,6 @@ static void ieee80211_free_tid_rx(struct rcu_head *h) 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++) __skb_queue_purge(&tid_rx->reorder_buf[i]); kfree(tid_rx->reorder_buf); @@ -93,6 +91,12 @@ void ___ieee80211_stop_rx_ba_session(struct sta_info *sta, u16 tid, del_timer_sync(&tid_rx->session_timer); + /* make sure ieee80211_sta_reorder_release() doesn't re-arm the timer */ + spin_lock_bh(&tid_rx->reorder_lock); + tid_rx->removed = true; + spin_unlock_bh(&tid_rx->reorder_lock); + del_timer_sync(&tid_rx->reorder_timer); + call_rcu(&tid_rx->rcu_head, ieee80211_free_tid_rx); } diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c index bb77d6d7258a..631d59f540d1 100644 --- a/net/mac80211/rx.c +++ b/net/mac80211/rx.c @@ -808,9 +808,10 @@ static void ieee80211_sta_reorder_release(struct ieee80211_sub_if_data *sdata, set_release_timer: - mod_timer(&tid_agg_rx->reorder_timer, - tid_agg_rx->reorder_time[j] + 1 + - HT_RX_REORDER_BUF_TIMEOUT); + if (!tid_agg_rx->removed) + mod_timer(&tid_agg_rx->reorder_timer, + tid_agg_rx->reorder_time[j] + 1 + + HT_RX_REORDER_BUF_TIMEOUT); } else { del_timer(&tid_agg_rx->reorder_timer); } diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h index bcda2ac7d844..bdba4ca5e76a 100644 --- a/net/mac80211/sta_info.h +++ b/net/mac80211/sta_info.h @@ -170,6 +170,7 @@ struct tid_ampdu_tx { * @reorder_lock: serializes access to reorder buffer, see below. * @auto_seq: used for offloaded BA sessions to automatically pick head_seq_and * and ssn. + * @removed: this session is removed (but might have been found due to RCU) * * This structure's lifetime is managed by RCU, assignments to * the array holding it must hold the aggregation mutex. @@ -194,6 +195,7 @@ struct tid_ampdu_rx { u16 timeout; u8 dialog_token; bool auto_seq; + bool removed; }; /** -- cgit v1.2.3