[PATCH 4.4 23/28] mac80211: pause TX while changing interface type

[Greg Kroah-Hartman]

From: Johannes Berg <johannes.berg@xxxxxxxxx>

[ Upstream commit 054c9939b4800a91475d8d89905827bf9e1ad97a ]

syzbot reported a crash that happened when changing the interface
type around a lot, and while it might have been easy to fix just
the symptom there, a little deeper investigation found that really
the reason is that we allowed packets to be transmitted while in
the middle of changing the interface type.

Disallow TX by stopping the queues while changing the type.

Fixes: 34d4bc4d41d2 ("mac80211: support runtime interface type changes")
Reported-by: syzbot+d7a3b15976bf7de2238a@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20210122171115.b321f98f4d4f.I6997841933c17b093535c31d29355be3c0c39628@changeid
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/mac80211/ieee80211_i.h | 1 +
 net/mac80211/iface.c       | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index a991d1df6774d..1046520d726d8 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1027,6 +1027,7 @@ enum queue_stop_reason {
 	IEEE80211_QUEUE_STOP_REASON_FLUSH,
 	IEEE80211_QUEUE_STOP_REASON_TDLS_TEARDOWN,
 	IEEE80211_QUEUE_STOP_REASON_RESERVE_TID,
+	IEEE80211_QUEUE_STOP_REASON_IFTYPE_CHANGE,
 
 	IEEE80211_QUEUE_STOP_REASONS,
 };
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 519def0e15f17..6d12a893eb11c 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -1507,6 +1507,10 @@ static int ieee80211_runtime_change_iftype(struct ieee80211_sub_if_data *sdata,
 	if (ret)
 		return ret;
 
+	ieee80211_stop_vif_queues(local, sdata,
+				  IEEE80211_QUEUE_STOP_REASON_IFTYPE_CHANGE);
+	synchronize_net();
+
 	ieee80211_do_stop(sdata, false);
 
 	ieee80211_teardown_sdata(sdata);
@@ -1527,6 +1531,8 @@ static int ieee80211_runtime_change_iftype(struct ieee80211_sub_if_data *sdata,
 	err = ieee80211_do_open(&sdata->wdev, false);
 	WARN(err, "type change: do_open returned %d", err);
 
+	ieee80211_wake_vif_queues(local, sdata,
+				  IEEE80211_QUEUE_STOP_REASON_IFTYPE_CHANGE);
 	return ret;
 }
 
-- 
2.27.0