From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 177632FC4E; Fri, 24 Nov 2023 18:36:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="F3TFRgkr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9A78FC433C7; Fri, 24 Nov 2023 18:36:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1700850982; bh=xozVkcaEh7iPhAoLiWEGHAGBJgNMAmTGUepq5Kiux5M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=F3TFRgkrsJO0yoWcIJLesPHUm9eDMkScYYmM2qjqHJ86J0eX/wDUx9EaEW1tWIew/ mfeQlo93FTOOxu7qoyqvRb6RGBWOmIf8LGCrDe8D1MtpmfMZWQK3IgF5Cz12BSIBcK cnLrQQIkYy1hoW1RgW5+Ex7rIrqJRS3gDIaTR8iU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, SeongJae Park , Jakub Acs , Andrew Morton Subject: [PATCH 6.5 266/491] mm/damon/core: avoid divide-by-zero during monitoring results update Date: Fri, 24 Nov 2023 17:48:22 +0000 Message-ID: <20231124172032.560975028@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231124172024.664207345@linuxfoundation.org> References: <20231124172024.664207345@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.5-stable review patch. If anyone has any objections, please let me know. ------------------ From: SeongJae Park commit d35963bfb05877455228ecec6b194f624489f96a upstream. 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 Reported-by: Jakub Acs Cc: [6.3+] Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/damon/core.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) --- a/mm/damon/core.c +++ b/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,