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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8B104C38145 for ; Wed, 7 Sep 2022 21:45:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229976AbiIGVpc (ORCPT ); Wed, 7 Sep 2022 17:45:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60968 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230240AbiIGVp3 (ORCPT ); Wed, 7 Sep 2022 17:45:29 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E51947539A for ; Wed, 7 Sep 2022 14:45:27 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 69D93B81F29 for ; Wed, 7 Sep 2022 21:45:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6990CC433D6; Wed, 7 Sep 2022 21:45:24 +0000 (UTC) Date: Wed, 7 Sep 2022 17:46:04 -0400 From: Steven Rostedt To: Brian Norris Cc: Greg Kroah-Hartman , "Rafael J . Wysocki" , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] tracefs: Only clobber mode/uid/gid on remount if asked Message-ID: <20220907174604.06809ff2@gandalf.local.home> In-Reply-To: <20220826174353.2.Iab6e5ea57963d6deca5311b27fb7226790d44406@changeid> References: <20220826174353.1.Icbd40fce59f55ad74b80e5d435ea233579348a78@changeid> <20220826174353.2.Iab6e5ea57963d6deca5311b27fb7226790d44406@changeid> 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 Fri, 26 Aug 2022 17:44:17 -0700 Brian Norris wrote: > Users may have explicitly configured their tracefs permissions; we > shouldn't overwrite those just because a second mount appeared. > > Only clobber if the options were provided at mount time. > > Note: the previous behavior was especially surprising in the presence of > automounted /sys/kernel/debug/tracing/. > > # Don't change /sys/kernel/tracing/ permissions on automount. > umount /sys/kernel/debug/tracing/ BTW, I noticed that the above doesn't do anything. That is, you cannot unmount tracefs from /sys/kernel/debug/tracing. # ls /sys/kernel/debug/tracing/ available_events buffer_total_size_kb error_log hwlat_detector options recursed_functions set_event_notrace_pid set_ftrace_pid stack_trace trace_clock trace_stat uprobe_events available_filter_functions current_tracer eval_map instances osnoise saved_cmdlines set_event_pid set_graph_function stack_trace_filter trace_marker tracing_cpumask uprobe_profile available_tracers dynamic_events events kprobe_events per_cpu saved_cmdlines_size set_ftrace_filter set_graph_notrace synthetic_events trace_marker_raw tracing_max_latency user_events_data buffer_percent dyn_ftrace_total_info free_buffer kprobe_profile printk_formats saved_tgids set_ftrace_notrace snapshot timestamp_mode trace_options tracing_on user_events_status buffer_size_kb enabled_functions function_profile_enabled max_graph_depth README set_event set_ftrace_notrace_pid stack_max_size trace trace_pipe tracing_thresh # umount /sys/kernel/debug/tracing/ # ls /sys/kernel/debug/tracing/ available_events buffer_total_size_kb error_log hwlat_detector options recursed_functions set_event_notrace_pid set_ftrace_pid stack_trace trace_clock trace_stat uprobe_events available_filter_functions current_tracer eval_map instances osnoise saved_cmdlines set_event_pid set_graph_function stack_trace_filter trace_marker tracing_cpumask uprobe_profile available_tracers dynamic_events events kprobe_events per_cpu saved_cmdlines_size set_ftrace_filter set_graph_notrace synthetic_events trace_marker_raw tracing_max_latency user_events_data buffer_percent dyn_ftrace_total_info free_buffer kprobe_profile printk_formats saved_tgids set_ftrace_notrace snapshot timestamp_mode trace_options tracing_on user_events_status buffer_size_kb enabled_functions function_profile_enabled max_graph_depth README set_event set_ftrace_notrace_pid stack_max_size trace trace_pipe tracing_thresh -- Steve > stat /sys/kernel/debug/tracing/. > > # Don't change /sys/kernel/tracing/ permissions. > mount -t tracefs none /mnt/foo > > # Change /sys/kernel/tracing/ mode and uid, but not gid. > mount -t tracefs -o uid=bar,mode=0750 none /mnt/baz > > Signed-off-by: Brian Norris > --- >