ksmbd: allocate one more byte for implied bcc[0]

ksmbd_smb2_check_message allows client to return one byte more, so we
need to allocate additional memory in ksmbd_conn_handler_loop to avoid
out-of-bound access.

Cc: stable@vger.kernel.org
Signed-off-by: NChih-Yen Chang <cc85nod@gmail.com>
Acked-by: NNamjae Jeon <linkinjeon@kernel.org>
Signed-off-by: NSteve French <stfrench@microsoft.com>

fs/ksmbd/connection.c

@@ -351,7 +351,8 @@ int ksmbd_conn_handler_loop(void *p)
 			break;
 
 		/* 4 for rfc1002 length field */
-		size = pdu_size + 4;
+		/* 1 for implied bcc[0] */
+		size = pdu_size + 4 + 1;
 		conn->request_buf = kvmalloc(size, GFP_KERNEL);
 		if (!conn->request_buf)
 			break;