From 9c7e51b94709f6aaf24a32bd267e75e89f3a0b2c Mon Sep 17 00:00:00 2001 From: Ying Hsu Date: Wed, 31 May 2023 03:44:56 +0000 Subject: [PATCH] Bluetooth: Fix l2cap_disconnect_req deadlock [ Upstream commit 02c5ea5246a44d6ffde0fddebfc1d56188052976 ] L2CAP assumes that the locks conn->chan_lock and chan->lock are acquired in the order conn->chan_lock, chan->lock to avoid potential deadlock. For example, l2sock_shutdown acquires these locks in the order: mutex_lock(&conn->chan_lock) l2cap_chan_lock(chan) However, l2cap_disconnect_req acquires chan->lock in l2cap_get_chan_by_scid first and then acquires conn->chan_lock before calling l2cap_chan_del. This means that these locks are acquired in unexpected order, which leads to potential deadlock: l2cap_chan_lock(c) mutex_lock(&conn->chan_lock) This patch releases chan->lock before acquiring the conn_chan_lock to avoid the potential deadlock. Fixes: a2a9339e1c9d ("Bluetooth: L2CAP: Fix use-after-free in l2cap_disconnect_{req,rsp}") Signed-off-by: Ying Hsu Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin --- net/bluetooth/l2cap_core.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index ee8f806534df..1287de387bc5 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -4664,7 +4664,9 @@ static inline int l2cap_disconnect_req(struct l2cap_conn *conn, chan->ops->set_shutdown(chan); + l2cap_chan_unlock(chan); mutex_lock(&conn->chan_lock); + l2cap_chan_lock(chan); l2cap_chan_del(chan, ECONNRESET); mutex_unlock(&conn->chan_lock); @@ -4703,7 +4705,9 @@ static inline int l2cap_disconnect_rsp(struct l2cap_conn *conn, return 0; } + l2cap_chan_unlock(chan); mutex_lock(&conn->chan_lock); + l2cap_chan_lock(chan); l2cap_chan_del(chan, 0); mutex_unlock(&conn->chan_lock);