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=-11.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 0E91AC4727D for ; Mon, 5 Oct 2020 04:39:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B83CC2083B for ; Mon, 5 Oct 2020 04:39:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="COQqBmkQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725866AbgJEEjk (ORCPT ); Mon, 5 Oct 2020 00:39:40 -0400 Received: from m42-4.mailgun.net ([69.72.42.4]:27476 "EHLO m42-4.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725267AbgJEEjk (ORCPT ); Mon, 5 Oct 2020 00:39:40 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1601872779; h=Content-Transfer-Encoding: Content-Type: In-Reply-To: MIME-Version: Date: Message-ID: From: References: Cc: To: Subject: Sender; bh=n0KgKn/5gajY7HCxaeIkOKKATXMuFolbt/z+U2KsArA=; b=COQqBmkQ1rqHWjAWpYMqpDo2wUOo+K96nj0rjFTIkXpTxzu+DGDCVxbREp4kVvbpsR8Ejg6y 3hxe1M10M0/8J8v4wtrWHhAZOeOZAN5c+x09CJ2wrsY5Lo1o4z9i2Vdat/2mbxKUcR8k/9Go FyIK9GkZjxxIbweGaM649plwvDQ= X-Mailgun-Sending-Ip: 69.72.42.4 X-Mailgun-Sid: WyI0MWYwYSIsICJsaW51eC1rZXJuZWxAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n05.prod.us-west-2.postgun.com with SMTP id 5f7aa38ba03b63d6732c5a91 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Mon, 05 Oct 2020 04:39:39 GMT Sender: gkohli=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 507F6C433F1; Mon, 5 Oct 2020 04:39:39 +0000 (UTC) Received: from [192.168.1.4] (unknown [117.98.218.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: gkohli) by smtp.codeaurora.org (Postfix) with ESMTPSA id 988B9C433CA; Mon, 5 Oct 2020 04:39:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 988B9C433CA Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=gkohli@codeaurora.org Subject: Re: [PATCH v1] trace: Fix race in trace_open and buffer resize call To: rostedt@goodmis.org, linux-kernel@vger.kernel.org Cc: linux-arm-msm@vger.kernel.org, stable@vger.kernel.org References: <1600955705-27382-1-git-send-email-gkohli@codeaurora.org> From: Gaurav Kohli Message-ID: <71b8fe4c-7be2-fe51-cd84-890320c98cda@codeaurora.org> Date: Mon, 5 Oct 2020 10:09:34 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <1600955705-27382-1-git-send-email-gkohli@codeaurora.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Steven, please let us know, if below looks good to you or need modifications. Thanks Gaurav On 9/24/2020 7:25 PM, Gaurav Kohli wrote: > Below race can come, if trace_open and resize of > cpu buffer is running parallely on different cpus > CPUX CPUY > ring_buffer_resize > atomic_read(&buffer->resize_disabled) > tracing_open > tracing_reset_online_cpus > ring_buffer_reset_cpu > rb_reset_cpu > rb_update_pages > remove/insert pages > resetting pointer > This race can cause data abort or some times infinte loop in > rb_remove_pages and rb_insert_pages while checking pages > for sanity. > > Signed-off-by: Gaurav Kohli > Cc: stable@vger.kernel.org > --- > Changes since v0: > -Addressed Steven's review comments. > > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index 93ef0ab..15bf28b 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -4866,6 +4866,9 @@ void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu) > if (!cpumask_test_cpu(cpu, buffer->cpumask)) > return; > > + /* prevent another thread from changing buffer sizes */ > + mutex_lock(&buffer->mutex); > + > atomic_inc(&cpu_buffer->resize_disabled); > atomic_inc(&cpu_buffer->record_disabled); > > @@ -4876,6 +4879,8 @@ void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu) > > atomic_dec(&cpu_buffer->record_disabled); > atomic_dec(&cpu_buffer->resize_disabled); > + > + mutex_unlock(&buffer->mutex); > } > EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu); > > @@ -4889,6 +4894,9 @@ void ring_buffer_reset_online_cpus(struct trace_buffer *buffer) > struct ring_buffer_per_cpu *cpu_buffer; > int cpu; > > + /* prevent another thread from changing buffer sizes */ > + mutex_lock(&buffer->mutex); > + > for_each_online_buffer_cpu(buffer, cpu) { > cpu_buffer = buffer->buffers[cpu]; > > @@ -4907,6 +4915,8 @@ void ring_buffer_reset_online_cpus(struct trace_buffer *buffer) > atomic_dec(&cpu_buffer->record_disabled); > atomic_dec(&cpu_buffer->resize_disabled); > } > + > + mutex_unlock(&buffer->mutex); > } > > /** > -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.