From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_RED,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 597CBC48BCF for ; Wed, 9 Jun 2021 22:36:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 42A11613E3 for ; Wed, 9 Jun 2021 22:36:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230322AbhFIWiv (ORCPT ); Wed, 9 Jun 2021 18:38:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:50162 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230205AbhFIWiu (ORCPT ); Wed, 9 Jun 2021 18:38:50 -0400 Received: from rorschach.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 685C26139A; Wed, 9 Jun 2021 22:36:55 +0000 (UTC) Date: Wed, 9 Jun 2021 18:36:53 -0400 From: Steven Rostedt To: Linus Torvalds Cc: Linux Kernel Mailing List , Ingo Molnar , Andrew Morton Subject: Re: [PATCH 1/2] tracing: Simplify the max length test when using the filtering temp buffer Message-ID: <20210609183653.0b77510c@rorschach.local.home> In-Reply-To: References: <20210609220457.220164154@goodmis.org> <20210609220537.927890401@goodmis.org> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 9 Jun 2021 15:21:52 -0700 Linus Torvalds wrote: > On Wed, Jun 9, 2021 at 3:05 PM Steven Rostedt wrote: > > > > val = this_cpu_inc_return(trace_buffered_event_cnt); > > - if ((len < (PAGE_SIZE - sizeof(*entry) - sizeof(entry->array[0]))) && val == 1) { > > + if (val == 1 && unlikely(len < max_len)) { > > unlikely? No. Bah, that was suppose to be "likely()" :-p > > Also, I still think that "len < max_len" should actually be "len <= > max_len". It should be ok to use the whole page, no? Sure, I was still being paranoid. ;-) > > Unless there is some *other* overflow issue, and "len" doesn't contain > a terminating NUL character or something like that. > No, this is kind of like an internal "malloc", where the caller is passing in the length via "len" of what it needs. -- Steve