[PATCH 5.15.y 2/3] Bluetooth: L2CAP: Fix deadlock in l2cap_conn_del()

[Sasha Levin <sashal@kernel.org>]

From: Hyunwoo Kim <imv4bel@gmail.com>

[ Upstream commit 00fdebbbc557a2fc21321ff2eaa22fd70c078608 ]

l2cap_conn_del() calls cancel_delayed_work_sync() for both info_timer
and id_addr_timer while holding conn->lock. However, the work functions
l2cap_info_timeout() and l2cap_conn_update_id_addr() both acquire
conn->lock, creating a potential AB-BA deadlock if the work is already
executing when l2cap_conn_del() takes the lock.

Move the work cancellations before acquiring conn->lock and use
disable_delayed_work_sync() to additionally prevent the works from
being rearmed after cancellation, consistent with the pattern used in
hci_conn_del().

Fixes: ab4eedb790ca ("Bluetooth: L2CAP: Fix corrupted list in hci_chan_del")
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Stable-dep-of: 2641a9e0a1dd ("Bluetooth: L2CAP: cancel pending_rx_work before taking conn->lock")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/bluetooth/l2cap_core.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index b3eb416eaebd18..09f1ea2d81bca5 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -1896,6 +1896,9 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
 
 	BT_DBG("hcon %p conn %p, err %d", hcon, conn, err);
 
+	cancel_delayed_work_sync(&conn->info_timer);
+	cancel_work_sync(&conn->id_addr_update_work);
+
 	kfree_skb(conn->rx_skb);
 
 	skb_queue_purge(&conn->pending_rx);
@@ -1909,9 +1912,6 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
 
 	ida_destroy(&conn->tx_ida);
 
-	if (work_pending(&conn->id_addr_update_work))
-		cancel_work_sync(&conn->id_addr_update_work);
-
 	l2cap_unregister_all_users(conn);
 
 	/* Force the connection to be immediately dropped */
@@ -1936,9 +1936,6 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
 
 	hci_chan_del(conn->hchan);
 
-	if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_SENT)
-		cancel_delayed_work_sync(&conn->info_timer);
-
 	hcon->l2cap_data = NULL;
 	conn->hchan = NULL;
 	l2cap_conn_put(conn);
-- 
2.53.0