Commit 3cfdf8fc authored by Thadeu Lima de Souza Cascardo's avatar Thadeu Lima de Souza Cascardo Committed by Marcel Holtmann

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: default avatarThadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: default avatarMarcel Holtmann <marcel@holtmann.org>
parent 44e936d7
......@@ -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);
......
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