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=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 EAFE4C4338F for ; Thu, 22 Jul 2021 22:13:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CFAF560EB9 for ; Thu, 22 Jul 2021 22:13:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232272AbhGVVce (ORCPT ); Thu, 22 Jul 2021 17:32:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:52644 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231902AbhGVVcd (ORCPT ); Thu, 22 Jul 2021 17:32:33 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 16A8260EB4; Thu, 22 Jul 2021 22:13:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1626991987; bh=K/zgg60QxsD92H9u2p0eB3H/DhqLEWBtU80nyuCM96Y=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=FdlsIoiAeOmoonbiA7TM+OB9x5Oqyrfk1PjdOyNOk3ujdil9NMOzw7xx1AkNf+PkC 11AR2mwAu63ujUHrEoScbK1RopgaEgOauOAivX46FxvqrQmNLqG2YXBv8asW9UI/Sy Dz7G4EWKVDowthOyiN52VyJ0nDNX0VHun6wQEGWSDxtpth3/cAC0r/KgS9mIW2PDCG e5wpWOTs9QVFGOMp5wuZQXpnY4663kvWDqjmJob4nr3XUIr53Z5l7Dgq+cFBPVmqvE wp1snKZJs547XrHwVvI1v0bvls6NajjRPlVBIZRby3VFn/3HBf7LsVu7pbib8l3rYR B5ClXoI8iMvKQ== Message-ID: <044507ec2dc4046f53e32cffbdb6d827205b22bc.camel@kernel.org> Subject: Re: [PATCH] tracing: Synthetic event field_pos is an index not a boolean From: Tom Zanussi To: Steven Rostedt , LKML Cc: Masami Hiramatsu , Namhyung Kim , Ingo Molnar , Andrew Morton Date: Thu, 22 Jul 2021 17:13:05 -0500 In-Reply-To: <20210721191008.638bce34@oasis.local.home> References: <20210721191008.638bce34@oasis.local.home> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Steve, On Wed, 2021-07-21 at 19:10 -0400, Steven Rostedt wrote: > From: "Steven Rostedt (VMware)" > > Performing the following: > > ># echo 'wakeup_lat s32 pid; u64 delta; char wake_comm[]' > > synthetic_events > ># echo 'hist:keys=pid:__arg__1=common_timestamp.usecs' > > events/sched/sched_waking/trigger > ># echo > 'hist:keys=next_pid:pid=next_pid,delta=common_timestamp.usecs- > $__arg__1:onmatch(sched.sched_waking).trace(wakeup_lat,$pid,$delta,pr > ev_comm)'\ > > events/sched/sched_switch/trigger > ># echo 1 > events/synthetic/enable > > Crashed the kernel: > > BUG: kernel NULL pointer dereference, address: 000000000000001b > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 0 P4D 0 > Oops: 0000 [#1] PREEMPT SMP > CPU: 7 PID: 0 Comm: swapper/7 Not tainted 5.13.0-rc5-test+ #104 > Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 > v03.03 07/14/2016 > RIP: 0010:strlen+0x0/0x20 > Code: f6 82 80 2b 0b bc 20 74 11 0f b6 50 01 48 83 c0 01 f6 82 80 2b > 0b bc > 20 75 ef c3 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 <80> 3f 00 > 74 10 > 48 89 f8 48 83 c0 01 80 38 9 f8 c3 31 > RSP: 0018:ffffaa75000d79d0 EFLAGS: 00010046 > RAX: 0000000000000002 RBX: ffff9cdb55575270 RCX: 0000000000000000 > RDX: ffff9cdb58c7a320 RSI: ffffaa75000d7b40 RDI: 000000000000001b > RBP: ffffaa75000d7b40 R08: ffff9cdb40a4f010 R09: ffffaa75000d7ab8 > R10: ffff9cdb4398c700 R11: 0000000000000008 R12: ffff9cdb58c7a320 > R13: ffff9cdb55575270 R14: ffff9cdb58c7a000 R15: 0000000000000018 > FS: 0000000000000000(0000) GS:ffff9cdb5aa00000(0000) > knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 000000000000001b CR3: 00000000c0612006 CR4: 00000000001706e0 > Call Trace: > trace_event_raw_event_synth+0x90/0x1d0 > action_trace+0x5b/0x70 > event_hist_trigger+0x4bd/0x4e0 > ? cpumask_next_and+0x20/0x30 > ? update_sd_lb_stats.constprop.0+0xf6/0x840 > ? __lock_acquire.constprop.0+0x125/0x550 > ? find_held_lock+0x32/0x90 > ? sched_clock_cpu+0xe/0xd0 > ? lock_release+0x155/0x440 > ? update_load_avg+0x8c/0x6f0 > ? enqueue_entity+0x18a/0x920 > ? __rb_reserve_next+0xe5/0x460 > ? ring_buffer_lock_reserve+0x12a/0x3f0 > event_triggers_call+0x52/0xe0 > trace_event_buffer_commit+0x1ae/0x240 > trace_event_raw_event_sched_switch+0x114/0x170 > __traceiter_sched_switch+0x39/0x50 > __schedule+0x431/0xb00 > schedule_idle+0x28/0x40 > do_idle+0x198/0x2e0 > cpu_startup_entry+0x19/0x20 > secondary_startup_64_no_verify+0xc2/0xcb > > The reason is that the dynamic events array keeps track of the field > position of the fields array, via the field_pos variable in the > synth_field structure. Unfortunately, that field is a boolean for > some > reason, which means any field_pos greater than 1 will be a bug (in > this > case it was 2). > > Cc: stable@vger.kernel.org > Fixes: bd82631d7ccdc ("tracing: Add support for dynamic strings to > synthetic events") > Signed-off-by: Steven Rostedt (VMware) > --- > kernel/trace/trace_synth.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/trace/trace_synth.h b/kernel/trace/trace_synth.h > index 6e146b959dcd..4007fe95cf42 100644 > --- a/kernel/trace/trace_synth.h > +++ b/kernel/trace/trace_synth.h > @@ -14,10 +14,10 @@ struct synth_field { > char *name; > size_t size; > unsigned int offset; > + unsigned int field_pos; > bool is_signed; > bool is_string; > bool is_dynamic; > - bool field_pos; > }; > > struct synth_event { Good catch, thanks, Reviewed-by: Tom Zanussi