6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Juan Perdomo [ Upstream commit 801fb950cae7048eb7d83b18857d1ca37b8cd5a4 ] rfcomm_sock_cleanup_listen() closes unaccepted child sockets through rfcomm_sock_close(), which takes the child socket lock before rfcomm_dlc_close() acquires rfcomm_mutex. The RFCOMM worker takes these locks in reverse order while handling connections and DLC state changes, so lockdep reports a possible deadlock. Close dequeued children without taking their socket lock. The accept queue owns a reference to each child, and bt_accept_dequeue() locks the child while unlinking it and clearing its parent pointer. Dropping the child lock makes it important to prevent a concurrent rfcomm_connect_ind() from enqueueing a new child after cleanup observes an empty queue. Set a listening socket to BT_CLOSED while its lock is still held, before dropping the lock and draining the queue. The state check in rfcomm_connect_ind() then rejects new children once cleanup starts. Reported-by: syzbot+0cece8fa7d83523f47a3@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=0cece8fa7d83523f47a3 Fixes: b7ce436a5d79 ("Bluetooth: switch to lock_sock in RFCOMM") Signed-off-by: Juan Perdomo Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin --- net/bluetooth/rfcomm/sock.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c index d72cdcd2e2bb1..729c70c992cfa 100644 --- a/net/bluetooth/rfcomm/sock.c +++ b/net/bluetooth/rfcomm/sock.c @@ -243,9 +243,7 @@ static void __rfcomm_sock_close(struct sock *sk) */ static void rfcomm_sock_close(struct sock *sk) { - lock_sock(sk); __rfcomm_sock_close(sk); - release_sock(sk); } static void rfcomm_sock_init(struct sock *sk, struct sock *parent) @@ -903,6 +901,7 @@ static int rfcomm_sock_compat_ioctl(struct socket *sock, unsigned int cmd, unsig static int rfcomm_sock_shutdown(struct socket *sock, int how) { struct sock *sk = sock->sk; + bool cleanup_listen = false; int err = 0; BT_DBG("sock %p, sk %p", sock, sk); @@ -913,9 +912,17 @@ static int rfcomm_sock_shutdown(struct socket *sock, int how) lock_sock(sk); if (!sk->sk_shutdown) { sk->sk_shutdown = SHUTDOWN_MASK; + if (sk->sk_state == BT_LISTEN) { + /* Block new children before cleaning up without sk lock. */ + sk->sk_state = BT_CLOSED; + cleanup_listen = true; + } release_sock(sk); - __rfcomm_sock_close(sk); + if (cleanup_listen) + rfcomm_sock_cleanup_listen(sk); + else + __rfcomm_sock_close(sk); lock_sock(sk); if (sock_flag(sk, SOCK_LINGER) && sk->sk_lingertime && -- 2.53.0