ksmbd: conn lock to serialize smb2 negotiate

If client send parallel smb2 negotiate request on same connection,
ksmbd_conn can be racy. smb2 negotiate handling that are not
performance-related can be serialized with conn lock.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: namjaejeon

fs/smb/server/smb2pdu.c

@@ -1097,6 +1097,7 @@ int smb2_handle_negotiate(struct ksmbd_work *work)
 		return rc;
 	}
 
+	ksmbd_conn_lock(conn);
 	smb2_buf_len = get_rfc1002_len(work->request_buf);
 	smb2_neg_size = offsetof(struct smb2_negotiate_req, Dialects);
 	if (smb2_neg_size > smb2_buf_len) {
@@ -1247,6 +1248,7 @@ int smb2_handle_negotiate(struct ksmbd_work *work)
 	ksmbd_conn_set_need_negotiate(conn);
 
 err_out:
+	ksmbd_conn_unlock(conn);
 	if (rc)
 		rsp->hdr.Status = STATUS_INSUFFICIENT_RESOURCES;