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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 C59BBC4361B for ; Tue, 8 Dec 2020 17:54:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 74B7823B3E for ; Tue, 8 Dec 2020 17:54:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730769AbgLHRyX (ORCPT ); Tue, 8 Dec 2020 12:54:23 -0500 Received: from mail.kernel.org ([198.145.29.99]:41062 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726810AbgLHRyX (ORCPT ); Tue, 8 Dec 2020 12:54:23 -0500 Received: from gandalf.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 17E3223B7E; Tue, 8 Dec 2020 17:53:42 +0000 (UTC) Date: Tue, 8 Dec 2020 12:53:40 -0500 From: Steven Rostedt To: Tom Zanussi Cc: axelrasmussen@google.com, mhiramat@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 3/5] tracing: Update synth command errors Message-ID: <20201208125340.407150f2@gandalf.local.home> In-Reply-To: <44b9e471f0d3b77ab0a2bf11024e2e72c1f1a80d.camel@kernel.org> References: <8671adc7ce95ff1d5c7b037d371467e96f7f2914.1603723933.git.zanussi@kernel.org> <20201207201304.627bfe48@oasis.local.home> <44b9e471f0d3b77ab0a2bf11024e2e72c1f1a80d.camel@kernel.org> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; 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 Tue, 08 Dec 2020 11:34:41 -0600 Tom Zanussi wrote: > Unfortunately, you're correct, if you have a script that creates a > synthetic event without semicolons, this patchset will break it, as I > myself found out and fixed in patch 4 ([PATCH v3 4/5] selftests/ftrace: > Add synthetic event field separators) [4]. > > So whereas before this would work, even though it shouldn't have in the > first place: > > # echo 'wakeup_latency u64 lat pid_t pid char comm[16]' > > synthetic_events > > it now has to be: > > # echo 'wakeup_latency u64 lat; pid_t pid; char comm[16]' > > synthetic_events > > So yeah, this patchset fixes a set of parsing bugs for things that > shouldn't have been accepted as valid, but shouldn't break things that > are obviously valid. > > If it's too late to fix them, though, I guess we'll just have to live > with them, or some other option? I would suggest allowing the old interface work (with no new features, for backward compatibility), but new things like "char comm[16]" we require semicolons. One method to do this is to add to the start of reading the string, and checking if it has semicolons. If it does not, we create a new string with them, but make sure that the string does not include new changes. strncpy_from_user(buffer, user_buff, sizeof(buffer)); if (!strstr(buffer, ";")) { if (!audit_old_buffer(buffer)) goto error; insert_colons(buffer); } That is, if the buffer does not have semicolons, then check if it is a valid "old format", and if not, we error out. Otherwise, we insert the colons into the buffer, and process that as if the user put in colons: That is: echo 'wakeup_latency u64 lat pid_t pid' > synthetic_events would change the buffer to: "wakeup_latency u64 lat; pid_t pid;" And then put it through the normal processing. I think its OK that if the user were to cat out the synthetic events, it would see the semicolons even if it did not add them. As I don't think that will break userspace. Does that make sense? -- Steve