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 8bf9c0e..8e281c2 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 3b9ec4e..b31417f 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;
 }