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=-14.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 65D9CC433ED for ; Fri, 14 May 2021 13:45:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 49FE46145E for ; Fri, 14 May 2021 13:45:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230262AbhENNrF (ORCPT ); Fri, 14 May 2021 09:47:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42676 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231196AbhENNrF (ORCPT ); Fri, 14 May 2021 09:47:05 -0400 Received: from mail-ed1-x52c.google.com (mail-ed1-x52c.google.com [IPv6:2a00:1450:4864:20::52c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 21A96C061574 for ; Fri, 14 May 2021 06:45:54 -0700 (PDT) Received: by mail-ed1-x52c.google.com with SMTP id t15so7090402edr.11 for ; Fri, 14 May 2021 06:45:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=FT7xAOOytm9sb5zmwE8t/9eJXx5zLF+21Yj5ULENmRE=; b=n2rOQd0AUb0QQBtwH7Ay0OXa0fR4NiOfe7uD34monSmwrUlNXdnKrsZZ4KA+CJZ5Ub t+Vpb8jPKX2+KLUdDdDQPwPsPyqDTD25/ZodFbDeBs07oYwB4HGCRYoXQUhCiun6yXlm 4GzhMEs0agodZ++M3bUgFDG5YWhcBZA49he3AqVj7Mco/xnDonbEVNhQu9UU7Fl8wsuB tIeEg59JztrYf/LmNImUbp7xQtslCYWzwpV9vTqbsJy/0viLmaLbJRdgYzZqVSRQYDgg thblKmkkQadicZahfYZiJ7CwWvBq4hgfmK8otPbXOoiBNDZDvSG6WAtPNlx5fNX1WJIp CxEw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=FT7xAOOytm9sb5zmwE8t/9eJXx5zLF+21Yj5ULENmRE=; b=mfQdNCmQCGOl0s/QxtxygwATi0IrtqAPm5PAaCmZUdYuDn702ib+7bvd7EMe7Cb+U8 rO1jXVTmARjXI3Y6BjOtky1CQOJfGr0p8J2BxPEMvdRSkiYIPuHBs7kN+fnhedqm5IE9 HrwHOj1o0avgudQPdSjjtXUAaelnq9AdwZkqtT6FiK+1jSQ7f/45+4PBI2uwycZHmL+c GEvgmpw2O5N8nNYTEUz9RrpuIQZDJwjm9meSavkIQ9s1rXFj1CXyXE0kR3KRhJjrQL3L 3ytCVz7GOLycsYXIyNc5OnN1w+lJeA1thk8/Gnf9PVaOKJ3vncrqzHKlvkD48nq+hhMo E9/A== X-Gm-Message-State: AOAM533wIa4BNtagrG3xvhanCvFMLdy83/P2XRahZ/aVdgdVirI1NOYq HCvN0doXe7ZdkaEKMmitEyQ+9vDVrYg= X-Google-Smtp-Source: ABdhPJzC/oyN9IhqHWc1y3Ti+fcOCoVL42HuT8wJS5mzRjcNkKnR35gLgGdx860kOXT0p4ui5kaKXw== X-Received: by 2002:a05:6402:350d:: with SMTP id b13mr56335278edd.21.1620999952694; Fri, 14 May 2021 06:45:52 -0700 (PDT) Received: from [192.168.0.106] ([84.40.73.176]) by smtp.gmail.com with ESMTPSA id h4sm4271056edv.97.2021.05.14.06.45.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 14 May 2021 06:45:52 -0700 (PDT) Subject: Re: [PATCH 6/7] kernel-shark: Check if "trace_seq" was destroyed before using it To: Steven Rostedt Cc: linux-trace-devel@vger.kernel.org References: <20210514121826.161749-1-y.karadz@gmail.com> <20210514121826.161749-7-y.karadz@gmail.com> <20210514093133.504d1008@gandalf.local.home> From: Yordan Karadzhov Message-ID: <29e3a3e1-26fe-a7e2-fec0-605794e2f353@gmail.com> Date: Fri, 14 May 2021 16:45:51 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210514093133.504d1008@gandalf.local.home> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org On 14.05.21 г. 16:31, Steven Rostedt wrote: > On Fri, 14 May 2021 15:18:25 +0300 > "Yordan Karadzhov (VMware)" wrote: > >> When closing a "tep" data stream we destroy the "trace_seq" object. >> However, trace_seq_destroy() sets the buffer to "TRACE_SEQ_POISON" >> which is different from NULL. >> >> It is unfortunate that TRACE_SEQ_POISON is an internal definition >> of libtraceevent, so we have to redefine it here, but this can be >> fixed in the future. > > It's not unfortunate. It can change in the future without breaking API. > > Redefining it here is not robust, and if trace-seq decides to do something > different with that poison value, this will break, and it can't be blamed > on API (using internal knowledge to implement code is not protected by > being backward compatible). > > The correct solution is to NULL the buffer after calling destroy. > > if (seq.buffer) { > trace_seq_destroy(&seq); > seq.buffer = NULL; > } This was the first fix I did when I found the problem, but I don't like it because it looks like a hack the the user of the library is doing to trick the internal logic of the library. Why not just moving the definition of TRACE_SEQ_POISON to the header or adding book trace_seq_is_destroyed() After this we can remove the clone from here. Thanks! Yordan > > Just like you would do with a pointer you free but may use NULL as a value > you are checking. > > -- Steve > > >> >> Signed-off-by: Yordan Karadzhov (VMware) >> --- >> src/libkshark-tepdata.c | 8 +++++++- >> 1 file changed, 7 insertions(+), 1 deletion(-) >> >> diff --git a/src/libkshark-tepdata.c b/src/libkshark-tepdata.c >> index bc5babb..4a84141 100644 >> --- a/src/libkshark-tepdata.c >> +++ b/src/libkshark-tepdata.c >> @@ -29,11 +29,17 @@ >> #include "libkshark-plugin.h" >> #include "libkshark-tepdata.h" >> >> +/** >> + * The TEP_SEQ_POISON is to catch the use of >> + * a trace_seq structure after it was destroyed. >> + */ >> +#define TEP_SEQ_POISON ((void *)0xdeadbeef) >> + >> static __thread struct trace_seq seq; >> >> static bool init_thread_seq(void) >> { >> - if (!seq.buffer) >> + if (!seq.buffer || seq.buffer == TEP_SEQ_POISON) >> trace_seq_init(&seq); >> >> return seq.buffer != NULL; >