From nobody Wed Dec 17 13:15:47 2025 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 139ABC46CA1 for ; Thu, 19 Oct 2023 19:49:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346569AbjJSTto (ORCPT ); Thu, 19 Oct 2023 15:49:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48238 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346517AbjJSTte (ORCPT ); Thu, 19 Oct 2023 15:49:34 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6FB5711F for ; Thu, 19 Oct 2023 12:49:33 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E6BB7C433C9; Thu, 19 Oct 2023 19:49:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697744973; bh=A7qQGX2x61HuX9WngSjrxy/tMdxThwG7cO+vlCnt/oI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lNgSoOfsk3ij3VEBkFziLTTOeodtOyWouwKEqFx+/Vc1mq4dpwxhRKSnXoRwsoucb xmeYm9yqQYBthSax96jDtI9ODtXEb7yTCOZCjdebg76CWIbn9yQVDy2jFkZj8rYXd7 oNq9xzrIQ25Tmf5XiVN2Aee+jPubzu3B3kxz7bjVCA4KdCtkt8pFLhJZjYzNyONzZQ PkVOy9fqQoNU8ok3jV6I4nU555Th406ewtAd/tBdhmST6Bpzl33dF6VUag7JudpLqA tc87Na/V54yov3Z36qOUQBq0gpwPA3O3j6ZH+zXwVdSxO1X3vjDD/8mnwLNYKGgs1n qQNgxlmk5W1XA== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 5/5] mm/damon/core: avoid divide-by-zero from pseudo-moving window length calculation Date: Thu, 19 Oct 2023 19:49:24 +0000 Message-Id: <20231019194924.100347-6-sj@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231019194924.100347-1-sj@kernel.org> References: <20231019194924.100347-1-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 calculating the pseudo-moving access rate, DAMON 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. Note that this is a fix for a commit that not in the mainline but mm tree. Fixes: ace30fb21af5 ("mm/damon/core: use pseudo-moving sum for nr_accesses_= bp") Signed-off-by: SeongJae Park --- Note that this is for a patch in mm-stable that not yet merged into the mainline. mm/damon/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index e194c8075235..aa2dc7087cd9 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -1665,7 +1665,7 @@ void damon_update_region_access_rate(struct damon_reg= ion *r, bool accessed, * aggr_interval, owing to validation of damon_set_attrs(). */ if (attrs->sample_interval) - len_window =3D attrs->aggr_interval / attrs->sample_interval; + len_window =3D damon_max_nr_accesses(attrs); r->nr_accesses_bp =3D damon_moving_sum(r->nr_accesses_bp, r->last_nr_accesses * 10000, len_window, accessed ? 10000 : 0); --=20 2.34.1