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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C2407CDB474 for ; Fri, 20 Oct 2023 17:18:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377895AbjJTRS6 (ORCPT ); Fri, 20 Oct 2023 13:18:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45002 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229683AbjJTRSv (ORCPT ); Fri, 20 Oct 2023 13:18:51 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E6A30A3; Fri, 20 Oct 2023 10:18:49 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 83AC2C433C8; Fri, 20 Oct 2023 17:18:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1697822329; bh=7qJXBEALo09kOtNdlPNLYg88qi7oMmUv55iQ1IROUmc=; h=Date:To:From:Subject:From; b=S5jnZr726AKxwQyXnIpp7xS6GTj3VydwUMkoYBfjvZDhWdqfTnQgu+vAfrLecBKsV VXlZygx3HmdKIuViektxLr87fMLNIlfxUVLc6ypz40EHZYcbdtKT1gDuKWIuzkp3U2 G3bE8XT+Pet4QzPUGbuvGrwRe5DAyM669ReOevI0= Date: Fri, 20 Oct 2023 10:18:48 -0700 To: mm-commits@vger.kernel.org, stable@vger.kernel.org, sj@kernel.org, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-damon-core-avoid-divide-by-zero-during-monitoring-results-update.patch added to mm-hotfixes-unstable branch Message-Id: <20231020171849.83AC2C433C8@smtp.kernel.org> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: mm/damon/core: avoid divide-by-zero during monitoring results update has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-damon-core-avoid-divide-by-zero-during-monitoring-results-update.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-core-avoid-divide-by-zero-during-monitoring-results-update.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: SeongJae Park Subject: mm/damon/core: avoid divide-by-zero during monitoring results update Date: Thu, 19 Oct 2023 19:49:21 +0000 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. Link: https://lkml.kernel.org/r/20231019194924.100347-3-sj@kernel.org Fixes: 2f5bef5a590b ("mm/damon/core: update monitoring results for new monitoring attributes") Signed-off-by: SeongJae Park Cc: [6.3+] Signed-off-by: Andrew Morton --- mm/damon/core.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) --- a/mm/damon/core.c~mm-damon-core-avoid-divide-by-zero-during-monitoring-results-update +++ a/mm/damon/core.c @@ -476,20 +476,14 @@ static unsigned int damon_age_for_new_at static unsigned int damon_accesses_bp_to_nr_accesses( unsigned int accesses_bp, struct damon_attrs *attrs) { - unsigned int max_nr_accesses = - attrs->aggr_interval / attrs->sample_interval; - - return accesses_bp * max_nr_accesses / 10000; + return accesses_bp * damon_max_nr_accesses(attrs) / 10000; } /* 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 = - attrs->aggr_interval / attrs->sample_interval; - - return nr_accesses * 10000 / max_nr_accesses; + return nr_accesses * 10000 / damon_max_nr_accesses(attrs); } static unsigned int damon_nr_accesses_for_new_attrs(unsigned int nr_accesses, _ Patches currently in -mm which might be from sj@kernel.org are mm-damon-implement-a-function-for-max-nr_accesses-safe-calculation.patch mm-damon-core-avoid-divide-by-zero-during-monitoring-results-update.patch mm-damon-ops-common-avoid-divide-by-zero-during-region-hotness-calculation.patch mm-damon-lru_sort-avoid-divide-by-zero-in-hot-threshold-calculation.patch