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 11D85C3B19F for ; Fri, 14 Feb 2020 16:47:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DF5E424670 for ; Fri, 14 Feb 2020 16:47:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581698860; bh=QvxfOGCLgdsLGPzOiRJcc1LAqqGhABSP+R7a3xTSzao=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Wv4S7IYE8jA+491KNWU387GM+0HkYkVO3P0vqkgzjhz7Fqve1UzyBob5aINc4VfV+ R9l09dW9QsEmQKNmwrNQiAM2wVaMHfTw6u4I8rTCpWnSOM9UPdFZ7aRH73vFD4MBCk NBl0nhykzy/xYGOtTtUnou476fYnPEIuk9GEDWeE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2394012AbgBNQrg (ORCPT ); Fri, 14 Feb 2020 11:47:36 -0500 Received: from mail.kernel.org ([198.145.29.99]:55010 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405280AbgBNQU4 (ORCPT ); Fri, 14 Feb 2020 11:20:56 -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 B66DA24717; Fri, 14 Feb 2020 16:20:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581697256; bh=QvxfOGCLgdsLGPzOiRJcc1LAqqGhABSP+R7a3xTSzao=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ypYdlj+WW/g0la7XAhasRZsTmBWCU2d0Kh7q3OXlRSfO7WlkFf+ez0iSrY1/xc4V0 cknP8AEcr7QJgfQL1ggQcPBkrcJil4Z60lZr8tmT3pAFwAQO9yGw9ZNythUAdYlWEq FuLaxmWbKkc+1O9ac8w32cLNgsfvIHVEFiYgEt2M= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Vasily Averin , Steven Rostedt , Sasha Levin Subject: [PATCH AUTOSEL 4.14 173/186] trigger_next should increase position index Date: Fri, 14 Feb 2020 11:17:02 -0500 Message-Id: <20200214161715.18113-173-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200214161715.18113-1-sashal@kernel.org> References: <20200214161715.18113-1-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 e2da180ca172a..31e91efe243e5 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -127,9 +127,10 @@ 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