mac80211: pause TX while changing interface type

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@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/20210122171115.b321f98f4d4f.I6997841933c17b093535c31d29355be3c0c39628@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 8bf9c0e974d6284390840970f0bdcecbd9476423..8e281c2e644d5ebc75aa4529e3bb996bea0c8fc1 100644 (file)
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1078,6 +1078,7 @@ 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 3b9ec4ef81c3baa6d44261dd339e4fe6964b56d9..b31417f40bd56f4df116c7b91647275883eb86a8 100644 (file)
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -1617,6 +1617,10 @@ 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);
@@ -1639,6 +1643,8 @@ 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;
 }