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=-9.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 7969DC43381 for ; Tue, 12 Mar 2019 17:42:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4FC9B206DF for ; Tue, 12 Mar 2019 17:42:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1552412533; bh=MMzbwjNBBVC9uIDfaXZPuvDFkEccPDKapdGfen7r+2A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=nJt4cN/Aie/pnvA9ll68ENG9X/0voxpH1z2kcKhw7YfD2mPfMgpuKZSXXtkEWCsEF Bwt1ic8mocFst8GjKRaX0zaZlvt6zbfBbad7Kg5uVBhAWRi84VwGgEiCASXq4Q+J0m RVYWa9VGNlzL7uMdyR1+lAvhxnGxnl2wW1rFBAQQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729695AbfCLRmM (ORCPT ); Tue, 12 Mar 2019 13:42:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:57266 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728964AbfCLRQA (ORCPT ); Tue, 12 Mar 2019 13:16:00 -0400 Received: from localhost (unknown [104.133.8.98]) (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 50D2A2183F; Tue, 12 Mar 2019 17:16:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1552410960; bh=MMzbwjNBBVC9uIDfaXZPuvDFkEccPDKapdGfen7r+2A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=M2Xln0WvGw6z+Epn/2GzpDCuZhe46u9iMOEI4Snml+I1kLbUnx1fqGnLqrZx9+GVG BvJlQD2iuqutoDMvp3tFYtFvwDYsufxQwQjZUt8DeVP4ml5lXRjyuFSRNhAYAUXlRh 4MLJoKXQE/jdPopDz6lWBpKkuZia3VfywjI18MN4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Stephane Eranian , Andi Kleen , Jiri Olsa , Arnaldo Carvalho de Melo , Kan Liang , Peter Zijlstra , Sasha Levin Subject: [PATCH 4.14 045/135] perf core: Fix perf_proc_update_handler() bug Date: Tue, 12 Mar 2019 10:08:12 -0700 Message-Id: <20190312170345.286983653@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190312170341.127810985@linuxfoundation.org> References: <20190312170341.127810985@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore 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 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ [ Upstream commit 1a51c5da5acc6c188c917ba572eebac5f8793432 ] The perf_proc_update_handler() handles /proc/sys/kernel/perf_event_max_sample_rate syctl variable. When the PMU IRQ handler timing monitoring is disabled, i.e, when /proc/sys/kernel/perf_cpu_time_max_percent is equal to 0 or 100, then no modification to sysctl_perf_event_sample_rate is allowed to prevent possible hang from wrong values. The problem is that the test to prevent modification is made after the sysctl variable is modified in perf_proc_update_handler(). You get an error: $ echo 10001 >/proc/sys/kernel/perf_event_max_sample_rate echo: write error: invalid argument But the value is still modified causing all sorts of inconsistencies: $ cat /proc/sys/kernel/perf_event_max_sample_rate 10001 This patch fixes the problem by moving the parsing of the value after the test. Committer testing: # echo 100 > /proc/sys/kernel/perf_cpu_time_max_percent # echo 10001 > /proc/sys/kernel/perf_event_max_sample_rate -bash: echo: write error: Invalid argument # cat /proc/sys/kernel/perf_event_max_sample_rate 10001 # Signed-off-by: Stephane Eranian Reviewed-by: Andi Kleen Reviewed-by: Jiri Olsa Tested-by: Arnaldo Carvalho de Melo Cc: Kan Liang Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1547169436-6266-1-git-send-email-eranian@google.com Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Sasha Levin --- kernel/events/core.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 17d5d41464c6..92939b5397df 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -436,18 +436,18 @@ int perf_proc_update_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { - int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); - - if (ret || !write) - return ret; - + int ret; + int perf_cpu = sysctl_perf_cpu_time_max_percent; /* * If throttling is disabled don't allow the write: */ - if (sysctl_perf_cpu_time_max_percent == 100 || - sysctl_perf_cpu_time_max_percent == 0) + if (write && (perf_cpu == 100 || perf_cpu == 0)) return -EINVAL; + ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + if (ret || !write) + return ret; + max_samples_per_tick = DIV_ROUND_UP(sysctl_perf_event_sample_rate, HZ); perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate; update_perf_cpu_limits(); -- 2.19.1