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 5A1AA3B71D7; Tue, 30 Jun 2026 04:26:23 +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=1782793584; cv=none; b=HYfD3Z1TMZplSHz4qwfUQ14AEuAgKQg53Ear2KVNtQQdheqRZhymeqvWb0J/AVt4hGJlWqP6mARKWz//aVpB6E7zCnmyLSnhNQ8IeF9RM29Hbyq9+vvRUDTHYePl1yfpAXmD+xvd4J6a/VKsfWInngR4XznnXdUgqA86WQgwdqI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782793584; c=relaxed/simple; bh=P6Uk7lHUNXnieCg17gonvdPUMm4uOU4L51FRPAwbrEI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pyeIp+QC3+gXhoFfzDyF9cczck6CZ7vYcljMGZFCs3dOt2infiVOpfv0om7CbvBamTurkUeUessZLzgTMGjNAK1XJULHGgSjlF5+zf6XziGvpm9wae/gR6wcKbPNmWrbX9LNVRX52fGTCg3CfgWm9XSeBai6sE/yht+yuq8MIFE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Q1Seo8Ff; 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="Q1Seo8Ff" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 02E081F000E9; Tue, 30 Jun 2026 04:26:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782793583; bh=Ae8t/Ilc5afoONBuaiJzpXJpdh+evRAuQt8lBfqqfFc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Q1Seo8Ffs3lw+ArmCzrhd6+ZuK+vKuYMzCkkcKrKjxwuJT0X3+DzQ2Awmfl08SI72 pIaCRoLbGkSpScHQFf3cHZXrZE7SX8T6cbsPSJsSdCA7QOZOubFE3WbK9N5Xuflktj AUJUIUfPmRsOkDNkIW5rAeKIPjhWe6T3AqAhXhyUDW3MKKKBHcUL5Zn9r+nkRAKn8a cz2W203yWDri1oey6bDLcrkSeF3Qd4TFZcPAaHcbpp/K617KHHh/uLB6HIqMIxCDeR aePKtHaldDnUpqJJIdXc+G7FPb6/UPvk5ym6qX9YRCVuERqhXrbxn4qBoJd4AWPoOe owd+xm28QDkmA== From: SJ Park To: SJ 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: [PATCH] mm/damon/core: validate ranges in damon_set_regions() Date: Mon, 29 Jun 2026 21:26:12 -0700 Message-ID: <20260630042612.151351-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260630035221.146458-1-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 Mon, 29 Jun 2026 20:52:19 -0700 SJ 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 > [...] > > All DAMON API callers eventually use damon_set_regions() to setup the > regions. Add the validation logic in the function. Sashiko found a pre-existing issue, and it is not a blocker of this patch in my opinion. Read my reply [1] to Sashiko review for more details. So this patch is good to go. [1] https://lore.kernel.org/20260630041806.151124-1-sj@kernel.org Thanks, SJ [...]