[PATCH v3 2/2 5.10.y, 5.15.y] Bluetooth: 6lowpan: Fix using chan->conn as indication to no remote netdev

From: Luiz Augusto von Dentz <[email protected]>

b66774b48dd9 ("Bluetooth: L2CAP: Fix UAF in channel timeout by holding
conn ref") don't reset the chan->conn to NULL anymore making the bt#
netdev not be remove once the last l2cap_chan_del is removed.

Instead of restoring the original behavior this remove the logic of
keeping the interface after the last channel is removed because it
never worked as intended and the l2cap_chan_del always detach its
l2cap_conn which results in always removing the channel anyway.

Fixes: b66774b48dd9 ("Bluetooth: L2CAP: Fix UAF in channel timeout by holding conn ref")
Signed-off-by: Luiz Augusto von Dentz <[email protected]>
---
v2:
- added this patch to the series which fixes 1/1

 net/bluetooth/6lowpan.c | 18 +++---------------
 1 file changed, 3 insertions(+), 15 deletions(-)

diff --git a/net/bluetooth/6lowpan.c b/net/bluetooth/6lowpan.c
index 9424d153f323fdfb1453d18ef7821ccddaeaa5eb..d0b1882f5b4b77d274580a0e8af7a3d43972615d 100644
--- a/net/bluetooth/6lowpan.c
+++ b/net/bluetooth/6lowpan.c
@@ -775,20 +775,10 @@ static void chan_close_cb(struct l2cap_chan *chan)
 	struct lowpan_btle_dev *dev = NULL;
 	struct lowpan_peer *peer;
 	int err = -ENOENT;
-	bool last = false, remove = true;
+	bool last = false;
 
 	BT_DBG("chan %p conn %p", chan, chan->conn);
 
-	if (chan->conn && chan->conn->hcon) {
-		if (!is_bt_6lowpan(chan->conn->hcon))
-			return;
-
-		/* If conn is set, then the netdev is also there and we should
-		 * not remove it.
-		 */
-		remove = false;
-	}
-
 	spin_lock(&devices_lock);
 
 	list_for_each_entry_rcu(entry, &bt_6lowpan_devices, list) {
@@ -815,10 +805,8 @@ static void chan_close_cb(struct l2cap_chan *chan)
 
 		ifdown(dev->netdev);
 
-		if (remove) {
-			INIT_WORK(&entry->delete_netdev, delete_netdev);
-			schedule_work(&entry->delete_netdev);
-		}
+		INIT_WORK(&entry->delete_netdev, delete_netdev);
+		schedule_work(&entry->delete_netdev);
 	} else {
 		spin_unlock(&devices_lock);
 	}
-- 
2.55.0.699.gb54405d56f-goog