[PATCH v2] Bluetooth: L2CAP: Fix deadlock in l2cap_conn_del()

[Hyunwoo Kim <imv4bel@gmail.com>]

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>
---
Changes in v2:
- Replace cancel_delayed_work_sync() with disable_delayed_work_sync()
- v1: https://lore.kernel.org/all/abwTQVhyDv0_x26G@v4bel/
---
 net/bluetooth/l2cap_core.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 5deb6c4f1e41..b279620ed209 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -1748,6 +1748,9 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
 
 	BT_DBG("hcon %p conn %p, err %d", hcon, conn, err);
 
+	disable_delayed_work_sync(&conn->info_timer);
+	disable_delayed_work_sync(&conn->id_addr_timer);
+
 	mutex_lock(&conn->lock);
 
 	kfree_skb(conn->rx_skb);
@@ -1763,8 +1766,6 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
 
 	ida_destroy(&conn->tx_ida);
 
-	cancel_delayed_work_sync(&conn->id_addr_timer);
-
 	l2cap_unregister_all_users(conn);
 
 	/* Force the connection to be immediately dropped */
@@ -1783,9 +1784,6 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
 		l2cap_chan_put(chan);
 	}
 
-	if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_SENT)
-		cancel_delayed_work_sync(&conn->info_timer);
-
 	hci_chan_del(conn->hchan);
 	conn->hchan = NULL;
 
-- 
2.43.0