From 8c8e620467a7b51562dbcefbd1f09f288d7d710d Mon Sep 17 00:00:00 2001 From: Siwei Zhang Date: Wed, 20 May 2026 22:12:20 -0400 Subject: [PATCH] Bluetooth: L2CAP: use chan timer to close channels in cleanup_listen() l2cap_chan_close() removes the channel from conn->chan_l, which must be done under conn->lock. cleanup_listen() runs under the parent sk_lock, so acquiring conn->lock would invert the established conn->lock -> chan->lock -> sk_lock order. Instead of calling l2cap_chan_close() directly, schedule l2cap_chan_timeout with delay 0 to close the channel asynchronously. The timeout handler already acquires conn->lock and chan->lock in the correct order. The timer is only armed when chan->conn is still set: if it is already NULL, l2cap_conn_del() has already processed this channel (l2cap_chan_del + l2cap_sock_teardown_cb + l2cap_sock_close_cb), so there is nothing left to do. If l2cap_conn_del() races in after the timer is armed, __clear_chan_timer() inside l2cap_chan_del() cancels it; if the timer has already fired, the handler returns harmlessly because chan->conn was cleared. Fixes: 3df91ea20e74 ("Bluetooth: Revert to mutexes from RCU list") Cc: # 0b58004: Bluetooth: fix UAF in l2cap_sock_cleanup_listen() vs l2cap_conn_del() Signed-off-by: Siwei Zhang Signed-off-by: Luiz Augusto von Dentz --- net/bluetooth/l2cap_sock.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index b34e7da8d906..c138aa4ae266 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -1499,6 +1499,10 @@ static void l2cap_sock_cleanup_listen(struct sock *parent) * pin it (hold_unless_zero() additionally skips a chan already past * its last reference). We then drop the sk lock before taking * chan->lock, so sk and chan locks are never held together. + * + * Since we cannot call l2cap_chan_close() without conn->lock, + * schedule l2cap_chan_timeout to close the channel; it already + * acquires conn->lock -> chan->lock in the correct order. */ while ((sk = bt_accept_dequeue(parent, NULL))) { struct l2cap_chan *chan; @@ -1516,14 +1520,12 @@ static void l2cap_sock_cleanup_listen(struct sock *parent) state_to_string(chan->state)); l2cap_chan_lock(chan); - __clear_chan_timer(chan); - l2cap_chan_close(chan, ECONNRESET); - /* l2cap_conn_del() may already have killed this socket - * (it sets SOCK_DEAD); skip the duplicate to avoid a - * double sock_put()/l2cap_chan_put(). + /* Since we cannot call l2cap_chan_close() without + * conn->lock, schedule its timer to trigger the close + * and cleanup of this channel. */ - if (!sock_flag(sk, SOCK_DEAD)) - l2cap_sock_kill(sk); + if (chan->conn) + __set_chan_timer(chan, 0); l2cap_chan_unlock(chan); l2cap_chan_put(chan);