From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 48FD4227EA4; Sat, 27 Jun 2026 17:26:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782581200; cv=none; b=W04g9EQzlcLajJJBZw18f0SRxp/pzOv+c18nBWZWJzBqpW6SJeyzYMrtYZbkdbIbKOF/mNlddyQYFEU1vzBe70ecSZoOk7zZ00xbgn+1+CKF6dk5H1tfiAxT15xn5DMFi/oLfmH1YqINVfAsKzarKwsPWJ7TOYiBHzReTzGGUKY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782581200; c=relaxed/simple; bh=qX6NZ+okwh2mZnH7WQDx5tvtSGr+dLkueoTmpTwKr2k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hdmpsCNw3jXRsrn361IyrVSpWXeCmCwd6cMsWCv/LIipidI6o4n/4ZwZLw9lX+UWWrUpPe06VUyvJyDsmTes4Fu7x2rObWU7/MJskg77ZcU/XlAEhuq0x7T+BnD7XAGPa1HZDzvCVhW71ZeJg/CgTZ10qpq0OHWilC3B0j/8u5E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Qmc6DOAw; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Qmc6DOAw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A0E7D1F000E9; Sat, 27 Jun 2026 17:26:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782581198; bh=FQEZdzMR4S9EJURSnXOi0A7QXVE9gI14e3OGLriAsys=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Qmc6DOAwKXcAP+pOtkC6rejUGyAHxjO/U5tybrHEyTyFKTp/3VjGhisml9GONUBhi emVNvUHwnVMSMfFdCRgYE8hWnnt8EYcJvfjfll5iFqw97elZpbMJIvcFvmoUF+T6Nu jNBi3Xpqv6fgwcTryQZ47RXt6hbbVWEAYReckGFTfyhOzFmy8/NrWM/yoqsJw1rqYU YeadqQfyZnrcsrlRp6Y9Yejto0hw9Y4nGfoimiAVXW+PQj+LAoA4yYOmy5lwwynmJD HSKqqg0MWiEYBeOAvxHpAomZGuvRX7AB5XqMMkwH7pPdij3KwDvM7M/fGH5jiVCdqN acnSntl1VPKug== From: SeongJae Park To: SeongJae Park Cc: Andrew Morton , Yang Yingliang , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org Subject: Re: [RFC PATCH] mm/damon/core: validate ranges in damon_set_regions() Date: Sat, 27 Jun 2026 10:26:31 -0700 Message-ID: <20260627172631.3923-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260627170057.1867-1-sj@kernel.org> References: Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Sat, 27 Jun 2026 10:00:56 -0700 SeongJae Park wrote: > DAMON core logic assumes zero length regions don't exist. However, a > few DAMON API callers including DAMON_SYSFS, DAMON_RECLAIM and > DAMON_LRU_SORT allow users to set empty monitoring target regions. This > could result in WARN_ONCE() on CONFIG_DAMON_DEBUG_SANITY enabled kernel, > and divide-by-zero from damon_merge_two_regions(). > > For example, the WANR_ONCE() can be triggered like below. > > # grep DAMON_DEBUG_SANITY /boot/config-$(uname -r) > # CONFIG_DAMON_DEBUG_SANITY=y > # damo start > # cd /sys/kernel/mm/damon/admin/kdamonds/0 > # echo 0 > contexts/0/targets/0/regions/0/start > # echo 0 > contexts/0/targets/0/regions/0/end > # echo commit > state > # dmesg > [....] > [ 73.705780] ------------[ cut here ]------------ > [ 73.707552] start 0 >= end 0 > [ 73.708452] WARNING: mm/damon/core.c:359 at damon_new_region+0x6e/0x80, CPU#1: kdamond.0/758 > [...] > > Disallow empty region user inputs by updating the validation logic. The above description is wrong, since this is not updating an existing validation but adding a new validation. > > Fixes: 43b0536cb471 ("mm/damon: introduce DAMON-based Reclamation (DAMON_RECLAIM)") > Cc: # 5.16.x > Signed-off-by: SeongJae Park > --- > mm/damon/core.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/mm/damon/core.c b/mm/damon/core.c > index 7e4b9affc5b06..b3100d7fa5596 100644 > --- a/mm/damon/core.c > +++ b/mm/damon/core.c > @@ -358,6 +358,11 @@ int damon_set_regions(struct damon_target *t, struct damon_addr_range *ranges, > unsigned int i; > int err; > > + for (i = 0; i < nr_ranges; i++) { > + if (ranges[i].start >= ranges[i].end) > + return -EINVAL; > + } > + Sashiko found [1] this is not complete, since eventually this function uses aligned addresses. I will address that in the next revision by doing the validation with the aligned addresses. [1] https://lore.kernel.org/20260627172406.3794-1-sj@kernel.org Thanks, SJ [...]