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 A900539866 for ; Thu, 19 Oct 2023 19:49:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CuUPzS+N" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A79ACC433C7; Thu, 19 Oct 2023 19:49:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697744970; bh=hrrza+crBd0RjMFZAgh+3yDyKNEWLMDaW4dbIT2n9jQ=; h=From:To:Cc:Subject:Date:From; b=CuUPzS+NiENfFW4IGkmjF1bIWMGzjCQS3iWVUOePE5rhfXDWxQte786cYVifxeVzx GrusnsW84WOyMJCPzhi3dOzPjSZbDevDjkyXI7MCiqo08/rKT0phGUitlODzcDpPvA DvtSZBqIgt3a6OilHFjCisaHGwHT4q7him0DbNN7eSOLHYaW+xrQcm5RQ/gr255Wr4 +idbbXK+i9HClhI5L3MD8qLFUwodlAdLn3hQC7Xp6A4mslYvrIeQv7J/RAgd1cYbh/ +KhbQCiGeuMhqyTDT0vc5ilNhJwDrMG5lYAE3kylIerEvyFdvggU2shT/VU/IZ5SKA a7DlWTT1r0r6Q== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 0/5] avoid divide-by-zero due to max_nr_accesses overflow Date: Thu, 19 Oct 2023 19:49:19 +0000 Message-Id: <20231019194924.100347-1-sj@kernel.org> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The maximum nr_accesses of given DAMON context can be calculated by dividing the aggregation interval by the sampling interval. Some logics in DAMON uses the maximum nr_accesses as a divisor. Hence, the value shouldn't be zero. Such case is avoided since DAMON avoids setting the agregation interval as samller than the sampling interval. However, since nr_accesses is unsigned int while the intervals are unsigned long, the maximum nr_accesses could be zero while casting. Avoid the divide-by-zero by implementing a function that handles the corner case (first patch), and replaces the vulnerable direct max nr_accesses calculations (remaining patches). Note that the patches for the replacements are divided for broken commits, to make backporting on required tres easier. Especially, the last patch is for a patch that not yet merged into the mainline but in mm tree. SeongJae Park (5): mm/damon: implement a function for max nr_accesses safe calculation mm/damon/core: avoid divide-by-zero during monitoring results update mm/damon/ops-common: avoid divide-by-zero during region hotness calculation mm/damon/lru_sort: avoid divide-by-zero in hot threshold calculation mm/damon/core: avoid divide-by-zero from pseudo-moving window length calculation include/linux/damon.h | 7 +++++++ mm/damon/core.c | 12 +++--------- mm/damon/lru_sort.c | 4 +--- mm/damon/ops-common.c | 5 ++--- 4 files changed, 13 insertions(+), 15 deletions(-) base-commit: e845524c56a529768a8793e96304db09134eafdf -- 2.34.1