From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753178AbaKZO1W (ORCPT ); Wed, 26 Nov 2014 09:27:22 -0500 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.227]:9750 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753153AbaKZO1I (ORCPT ); Wed, 26 Nov 2014 09:27:08 -0500 Date: Wed, 26 Nov 2014 09:27:06 -0500 From: Steven Rostedt To: Dan Carpenter Cc: Ingo Molnar , linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org Subject: Re: [patch] tracing: off by one in __trace_array_vprintk() Message-ID: <20141126092706.5d4038d4@gandalf.local.home> In-Reply-To: <20141126140621.GA18740@mwanda> References: <20141126140621.GA18740@mwanda> X-Mailer: Claws Mail 3.10.1 (GTK+ 2.24.25; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.118:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 26 Nov 2014 17:06:21 +0300 Dan Carpenter wrote: > This check says "goto out;" if we had to truncate the string. > > The "tbuffer" buffer has TRACE_BUF_SIZE bytes. The vsnprintf() function > returns the number of characters (not counting the NUL char) which would > have been printed if there were space. If we we tried to print > TRACE_BUF_SIZE characters, the last character would have been truncated > to make space for the NUL character so we should "goto out;". > Oh, and the NUL character is never copied. We copy the string into the buffer with: memcpy(&entry->buf, tbuffer, len); Where len does not include NUL, and why we add it ourselves. -- Steve