From: Thadeu Lima de Souza Cascardo Date: Tue, 13 Apr 2021 16:21:03 +0000 (-0300) Subject: Bluetooth: cmtp: fix file refcount when cmtp_attach_device fails X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=3cfdf8fcaafa62a4123f92eb0f4a72650da3a479;p=linux.git Bluetooth: cmtp: fix file refcount when cmtp_attach_device fails When cmtp_attach_device fails, cmtp_add_connection returns the error value which leads to the caller to doing fput through sockfd_put. But cmtp_session kthread, which is stopped in this path will also call fput, leading to a potential refcount underflow or a use-after-free. Add a refcount before we signal the kthread to stop. The kthread will try to grab the cmtp_session_sem mutex before doing the fput, which is held when get_file is called, so there should be no races there. Reported-by: Ryota Shiga Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Marcel Holtmann --- diff --git a/net/bluetooth/cmtp/core.c b/net/bluetooth/cmtp/core.c index 07cfa3249f83a..0a2d78e811cf5 100644 --- a/net/bluetooth/cmtp/core.c +++ b/net/bluetooth/cmtp/core.c @@ -392,6 +392,11 @@ int cmtp_add_connection(struct cmtp_connadd_req *req, struct socket *sock) if (!(session->flags & BIT(CMTP_LOOPBACK))) { err = cmtp_attach_device(session); if (err < 0) { + /* Caller will call fput in case of failure, and so + * will cmtp_session kthread. + */ + get_file(session->sock->file); + atomic_inc(&session->terminate); wake_up_interruptible(sk_sleep(session->sock->sk)); up_write(&cmtp_session_sem);