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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 9266BC55178 for ; Thu, 5 Nov 2020 23:47:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 31CDB21D7F for ; Thu, 5 Nov 2020 23:47:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604620044; bh=cHPyby7pAr8kcs5Rx52a5F9TaNyVrHGa7UCBfNWtirg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=hanKgdJN0dxeJpkJQFuC4grkUYF35irsC8ABmkgNPKjJtsFILbLntoEmijf6h5IKG WFIVG6gNGxWJ//cpgbiaLBdp4rdhTBFDnXYIuG4Oi1TsaBMULpyt5SqB87byPm92oZ B5b9nTAvrAfUf1eQKRzClIQGUpvzdIy9hxR3XYXI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732461AbgKEXrX (ORCPT ); Thu, 5 Nov 2020 18:47:23 -0500 Received: from mail.kernel.org ([198.145.29.99]:45860 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726801AbgKEXrW (ORCPT ); Thu, 5 Nov 2020 18:47:22 -0500 Received: from paulmck-ThinkPad-P72.home (50-39-104-11.bvtn.or.frontiernet.net [50.39.104.11]) (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 CE70320756; Thu, 5 Nov 2020 23:47:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604620042; bh=cHPyby7pAr8kcs5Rx52a5F9TaNyVrHGa7UCBfNWtirg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cYXFNrNcfDfo0+WAVqIfjD2ElsanHYyXMO8Di9RG1Pu6ikaevmTENFbIoofIjCFm/ Km0M9xxe6mxT1t42ghoS4Ru/9eRra3//eFZtS/xnerNCU1E8rYG1wy6OOAXXhcuyUr 6N9VuA2ojGuugqnXKcFcVslBUQWmhve0pc771Fb0= From: paulmck@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 01/28] refscale: Bounds-check module parameters Date: Thu, 5 Nov 2020 15:46:52 -0800 Message-Id: <20201105234719.23307-1-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20201105234658.GA23142@paulmck-ThinkPad-P72> References: <20201105234658.GA23142@paulmck-ThinkPad-P72> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" The default value for refscale.nreaders is -1, which results in the code setting the value to three-quarters of the number of CPUs. On single-CPU systems, this results in three-quarters of the value one, which the C language's integer arithmetic rounds to zero. This in turn results in a divide-by-zero error. This commit therefore adds bounds checking to the refscale module parameters, so that if they are less than one, they are set to the value one. Reported-by: kernel test robot Tested-by "Chen, Rong A" Signed-off-by: Paul E. McKenney --- kernel/rcu/refscale.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c index 952595c..fb5f20d 100644 --- a/kernel/rcu/refscale.c +++ b/kernel/rcu/refscale.c @@ -681,6 +681,12 @@ ref_scale_init(void) // Reader tasks (default to ~75% of online CPUs). if (nreaders < 0) nreaders = (num_online_cpus() >> 1) + (num_online_cpus() >> 2); + if (WARN_ONCE(loops <= 0, "%s: loops = %ld, adjusted to 1\n", __func__, loops)) + loops = 1; + if (WARN_ONCE(nreaders <= 0, "%s: nreaders = %d, adjusted to 1\n", __func__, nreaders)) + nreaders = 1; + if (WARN_ONCE(nruns <= 0, "%s: nruns = %d, adjusted to 1\n", __func__, nruns)) + nruns = 1; reader_tasks = kcalloc(nreaders, sizeof(reader_tasks[0]), GFP_KERNEL); if (!reader_tasks) { -- 2.9.5