From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752772AbaKZOGj (ORCPT ); Wed, 26 Nov 2014 09:06:39 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:20100 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750907AbaKZOGh (ORCPT ); Wed, 26 Nov 2014 09:06:37 -0500 Date: Wed, 26 Nov 2014 17:06:21 +0300 From: Dan Carpenter To: Steven Rostedt Cc: Ingo Molnar , linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org Subject: [patch] tracing: off by one in __trace_array_vprintk() Message-ID: <20141126140621.GA18740@mwanda> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: acsinet22.oracle.com [141.146.126.238] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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;". My other concern here was that a few lines later we do: entry->buf[len] = '\0'; I worried that maybe we were putting the NUL char past the end of the array but I wasn't smart enough to figure out the size of entry->buf[]. Signed-off-by: Dan Carpenter diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 42a822d..22af2ae 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2161,7 +2161,7 @@ __trace_array_vprintk(struct ring_buffer *buffer, } len = vsnprintf(tbuffer, TRACE_BUF_SIZE, fmt, args); - if (len > TRACE_BUF_SIZE) + if (len >= TRACE_BUF_SIZE) goto out; local_save_flags(flags);