From patchwork Thu Feb 27 13:36:30 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 230533 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=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 375C9C3F34D for ; Thu, 27 Feb 2020 13:43:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 10D94222C2 for ; Thu, 27 Feb 2020 13:43:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582810993; bh=dVXJL/T4dMys1FvCdbA1mV3mv1OraNsbPY9kEd0Rh5w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=yGghupulic6CfSXbxFH8uiAhKf23vVPpnrAIOJq0YLtFK0b3ae1w4EhMFJknsyGcb IpJcten8wJXsWTZwQrQQNQz5LSEuzdesoNSouVMxcQERzFDy33HJ8quW9bwGt1aTHR jcnHP5LRMEdfERTNYrJpZpt7J7dsnJs2//s3J8m8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729904AbgB0NnM (ORCPT ); Thu, 27 Feb 2020 08:43:12 -0500 Received: from mail.kernel.org ([198.145.29.99]:38320 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729615AbgB0NnK (ORCPT ); Thu, 27 Feb 2020 08:43:10 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 F3BCF20578; Thu, 27 Feb 2020 13:43:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582810989; bh=dVXJL/T4dMys1FvCdbA1mV3mv1OraNsbPY9kEd0Rh5w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fPFEJDpZ483yU8O+dU9atIaFubGRcvW+DwPxHr/jMA0bDKwfaOLDOh9t3hiWTE7en ndILiz87WnK5Tpp7bjHdn5nzzYgVNkoKkP5OM6r7QQ8PUUqR8i6FS51Vt6TOjURm2t /nbI5dNM/VK9KFl2bcslDC5Uc1BQPaX3uCjQiUXc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vasily Averin , "Steven Rostedt (VMware)" , Sasha Levin Subject: [PATCH 4.4 074/113] trigger_next should increase position index Date: Thu, 27 Feb 2020 14:36:30 +0100 Message-Id: <20200227132223.637889402@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200227132211.791484803@linuxfoundation.org> References: <20200227132211.791484803@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Vasily Averin [ Upstream commit 6722b23e7a2ace078344064a9735fb73e554e9ef ] if seq_file .next fuction does not change position index, read after some lseek can generate unexpected output. Without patch: # dd bs=30 skip=1 if=/sys/kernel/tracing/events/sched/sched_switch/trigger dd: /sys/kernel/tracing/events/sched/sched_switch/trigger: cannot skip to specified offset n traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist # Available triggers: # traceon traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist 6+1 records in 6+1 records out 206 bytes copied, 0.00027916 s, 738 kB/s Notice the printing of "# Available triggers:..." after the line. With the patch: # dd bs=30 skip=1 if=/sys/kernel/tracing/events/sched/sched_switch/trigger dd: /sys/kernel/tracing/events/sched/sched_switch/trigger: cannot skip to specified offset n traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist 2+1 records in 2+1 records out 88 bytes copied, 0.000526867 s, 167 kB/s It only prints the end of the file, and does not restart. Link: http://lkml.kernel.org/r/3c35ee24-dd3a-8119-9c19-552ed253388a@virtuozzo.com https://bugzilla.kernel.org/show_bug.cgi?id=206283 Signed-off-by: Vasily Averin Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Sasha Levin --- kernel/trace/trace_events_trigger.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c index 8be66a2b0cacf..6524920c6ebc8 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -121,9 +121,10 @@ static void *trigger_next(struct seq_file *m, void *t, loff_t *pos) { struct trace_event_file *event_file = event_file_data(m->private); - if (t == SHOW_AVAILABLE_TRIGGERS) + if (t == SHOW_AVAILABLE_TRIGGERS) { + (*pos)++; return NULL; - + } return seq_list_next(t, &event_file->triggers, pos); }