From: Ying Hsu Date: Wed, 31 May 2023 03:44:56 +0000 (+0000) Subject: Bluetooth: Fix l2cap_disconnect_req deadlock X-Git-Tag: v6.6-pxa1908~1089^2~14^2~3 X-Git-Url: https://git.dujemihanovic.xyz/?a=commitdiff_plain;h=02c5ea5246a44d6ffde0fddebfc1d56188052976;p=linux.git Bluetooth: Fix l2cap_disconnect_req deadlock 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 --- diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index 376b523c7b26..d9c4d26b2518 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -4663,7 +4663,9 @@ 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); @@ -4702,7 +4704,9 @@ 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);