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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 EFFE7C3B1A1 for ; Fri, 14 Feb 2020 16:36:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C8921217F4 for ; Fri, 14 Feb 2020 16:36:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581698216; bh=/5tkRGL7RFRgg+Lxu3NtXFouIi6LPnsmZ5Gf5BgDzf8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=kBW/aJAtT9LcsHOy+RrZTqXWgWDx1G2T8CqnWK1mLsocVSuJYAJYniSeGUK16Bf5I pMEh5i4NLihdsk3WZx/3wXJ9pIBXTB+DZnzhHNYvnrWMJDv6z3T1XHLCdEcz5FDWAm BzLYsfxHV+dt8df8qb+6ULv2ldO1oI8vqEVB2aAI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405810AbgBNQYG (ORCPT ); Fri, 14 Feb 2020 11:24:06 -0500 Received: from mail.kernel.org ([198.145.29.99]:60672 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405805AbgBNQYF (ORCPT ); Fri, 14 Feb 2020 11:24:05 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2A36324790; Fri, 14 Feb 2020 16:24:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581697444; bh=/5tkRGL7RFRgg+Lxu3NtXFouIi6LPnsmZ5Gf5BgDzf8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YOx9KsDMlfsBXWOEiURfv5rfPjiL53twn3i5EjpIQSdothVKC4TqyA3Z705XdHkun AnEo51fIyDm/msDmqN2dTmmOQoySlLFoFRbfyWKOWIFbGhUCf0bwTiiBAOYnWYbOb2 OSFASQyNzYDoV7VtFfA8gazhgemmka5PFuNi08Cs= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Vasily Averin , Steven Rostedt , Sasha Levin Subject: [PATCH AUTOSEL 4.9 130/141] trigger_next should increase position index Date: Fri, 14 Feb 2020 11:21:10 -0500 Message-Id: <20200214162122.19794-130-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200214162122.19794-1-sashal@kernel.org> References: <20200214162122.19794-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit 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 7e6971ba95417..8a88e85c8c615 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -126,9 +126,10 @@ 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