[PATCH 6.1 484/609] Bluetooth: 6lowpan: Fix using chan->conn as indication to no remote netdev

6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

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

[ Upstream commit d38eaf611839b85ade3dd3db309dbc8aaaaf0095 ]

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]>
Signed-off-by: Sasha Levin <[email protected]>
---
 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 e2196cf4f6f70..723ead2c04f16 100644
--- a/net/bluetooth/6lowpan.c
+++ b/net/bluetooth/6lowpan.c
@@ -781,20 +781,10 @@ 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) {
@@ -821,10 +811,8 @@ 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);
 	}
-- 
2.53.0