ksmbd: fix use-after-free in session logoff

commit 2fc9feff45d92a92cd5f96487655d5be23fb7e2b upstream.

The sess->user object can currently be in use by another thread, for
example if another connection has sent a session setup request to
bind to the session being free'd. The handler for that connection could
be in the smb2_sess_setup function which makes use of sess->user.

Signed-off-by: Sean Heelan <seanheelan@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Nazar Kalashnikov <sivartiwe@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c
index e3ea06aab8c1b5c84546069b3f25ae6edd5f2d43..5a405706694b3eda468b3f4be924b5eb1fda01ff 100644 (file)
--- a/fs/smb/server/smb2pdu.c
+++ b/fs/smb/server/smb2pdu.c
@@ -2253,10 +2253,6 @@ int smb2_session_logoff(struct ksmbd_work *work)
        sess->state = SMB2_SESSION_EXPIRED;
        up_write(&conn->session_lock);
 
-       if (sess->user) {
-               ksmbd_free_user(sess->user);
-               sess->user = NULL;
-       }
        ksmbd_all_conn_set_status(sess_id, KSMBD_SESS_NEED_NEGOTIATE);
 
        rsp->StructureSize = cpu_to_le16(4);