From nobody Sat Feb 7 23:43:28 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D070CC19F5C for ; Fri, 20 Oct 2023 17:23:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377930AbjJTRX3 (ORCPT ); Fri, 20 Oct 2023 13:23:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36980 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229909AbjJTRX0 (ORCPT ); Fri, 20 Oct 2023 13:23:26 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EA258D4C; Fri, 20 Oct 2023 10:23:24 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1487BC433C7; Fri, 20 Oct 2023 17:23:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697822604; bh=OyGTPA4KF2+eYVdgVawdmd836X4nvWEWuxM0J39C7SY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tibiLrMDEW1tJPRD83m27OwLCd/3DldWtN6HSY+GRNl2CN2/lGFqdA8TQQ727MbK1 RXghEBiUVpRYW2wWEiF2yiDTw4Mz9aUN/5jKYr74Dv/eki3xYKDE93RdSo9tqctrMh CQYh7C/JT6Pd/m/Lx4jnpiYh3AL+5ZGjJ0Dgwm8qeCTjxEkZ//jSvkKcBywnn8qJsk xIov6mao/lOfYVmBmQThgDh3lKi7Zq5LeWX+G0A45G30D5VHCYpRwm1A1Anhin9GeL YqhXZxPUTshcAwA2xiNxXzGXvG7BgM88reL/1z9rKcS6B3dNgRns0LUK1vsgdWaqlG PvGSzwlgnkpAg== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , Jakub Acs , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH v2 2/5] mm/damon/core: avoid divide-by-zero during monitoring results update Date: Fri, 20 Oct 2023 17:23:14 +0000 Message-Id: <20231020172317.64192-3-sj@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231020172317.64192-1-sj@kernel.org> References: <20231020172317.64192-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When monitoring attributes are changed, DAMON updates access rate of the monitoring results accordingly. For that, it divides some values by the maximum nr_accesses. However, due to the type of the related variables, simple division-based calculation of the divisor can return zero. As a result, divide-by-zero is possible. Fix it by using damon_max_nr_accesses(), which handles the case. Reported-by: Jakub Acs Fixes: 2f5bef5a590b ("mm/damon/core: update monitoring results for new moni= toring attributes") Cc: # 6.3.x Signed-off-by: SeongJae Park --- mm/damon/core.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 9f4f7c378cf3..e194c8075235 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -500,20 +500,14 @@ static unsigned int damon_age_for_new_attrs(unsigned = int age, static unsigned int damon_accesses_bp_to_nr_accesses( unsigned int accesses_bp, struct damon_attrs *attrs) { - unsigned int max_nr_accesses =3D - attrs->aggr_interval / attrs->sample_interval; - - return accesses_bp * max_nr_accesses / 10000; + return accesses_bp * damon_max_nr_accesses(attrs) / 10000; } =20 /* convert nr_accesses to access ratio in bp (per 10,000) */ static unsigned int damon_nr_accesses_to_accesses_bp( unsigned int nr_accesses, struct damon_attrs *attrs) { - unsigned int max_nr_accesses =3D - attrs->aggr_interval / attrs->sample_interval; - - return nr_accesses * 10000 / max_nr_accesses; + return nr_accesses * 10000 / damon_max_nr_accesses(attrs); } =20 static unsigned int damon_nr_accesses_for_new_attrs(unsigned int nr_access= es, --=20 2.34.1