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=-9.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 69160C433DF for ; Wed, 14 Oct 2020 17:37:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 19FE322227 for ; Wed, 14 Oct 2020 17:37:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389427AbgJNRhe (ORCPT ); Wed, 14 Oct 2020 13:37:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:57694 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389513AbgJNRha (ORCPT ); Wed, 14 Oct 2020 13:37:30 -0400 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 9D95822247; Wed, 14 Oct 2020 17:37:29 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.94) (envelope-from ) id 1kSkiO-002yFg-Ep; Wed, 14 Oct 2020 13:37:28 -0400 Message-ID: <20201014173728.325418951@goodmis.org> User-Agent: quilt/0.66 Date: Wed, 14 Oct 2020 13:36:49 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Masami Hiramatsu , stable@vger.kernel.org, Gaurav Kohli Subject: [for-next][PATCH 02/12] tracing: Fix race in trace_open and buffer resize call References: <20201014173647.955053902@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Gaurav Kohli 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. Take buffer lock to fix this. Link: https://lkml.kernel.org/r/1601976833-24377-1-git-send-email-gkohli@codeaurora.org Cc: stable@vger.kernel.org Fixes: b23d7a5f4a07a ("ring-buffer: speed up buffer resets by avoiding synchronize_rcu for each CPU") Signed-off-by: Gaurav Kohli Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/ring_buffer.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 93ef0ab6ea20..15bf28b13e50 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); } /** -- 2.28.0