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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 7A640C35641 for ; Fri, 21 Feb 2020 08:31:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4E8EF20578 for ; Fri, 21 Feb 2020 08:31:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582273866; bh=o+o0M9tu1mUFpsW0wcJx7bRm3a8dmU2NUuterE4EqvM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=si4PpiePrFfYxC8LA1p/Audu8elhqsS0EZD6zQcvCyykQKVSlNnUfsZs80pWEPfYh hzHV9VmhuxCyttNxUXCVvO5KjD6E0+MOWySMDfPWxlKS3oAFcd00rC0V5KHqsBkB/B w3DklvCgYSIf2V0DleJLBcAJz6c5Qmrq5xYy2Gzg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388850AbgBUIbF (ORCPT ); Fri, 21 Feb 2020 03:31:05 -0500 Received: from mail.kernel.org ([198.145.29.99]:51496 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733242AbgBUIOw (ORCPT ); Fri, 21 Feb 2020 03:14:52 -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 99EE320578; Fri, 21 Feb 2020 08:14:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582272892; bh=o+o0M9tu1mUFpsW0wcJx7bRm3a8dmU2NUuterE4EqvM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=a1BkZ84gdFnoiOS+uGordZUE5n9f72ayEpyD9ruHEHSL+2Etnm89qKjcnfBxPYR/E Zpr67HtEswV8oaVgsQJDl62KYZGhtDFYiozDKYdJjDMI4oG0kzsnlAwhaIlpZAOHGK yeii/YJ7NUYTAhjj9FxeOkHpJGdGk+pVpuvKDFHg= 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 5.4 314/344] trigger_next should increase position index Date: Fri, 21 Feb 2020 08:41:53 +0100 Message-Id: <20200221072418.600688688@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200221072349.335551332@linuxfoundation.org> References: <20200221072349.335551332@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 40106fff06a48..287d77eae59b3 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -116,9 +116,10 @@ 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); } -- 2.20.1