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 89B9C370D41; Sun, 13 Sep 2026 17:17:15 +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=1789319836; cv=none; b=ECDpstBhsm/gTKR4zLqBBKp5SZupGt0X2hk2xgZKp9TLslMiR4d3ikeY9b4yn1JGn9k+e5YaaVgCRKYw8XLCAfgijVFKtqymuy/pwW31HOSErF6lgv0f0nvhoifEWCxon3qpk/dkmxuC35qUm1845xJIwrxdeivt0WVCgf1VAI0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789319836; c=relaxed/simple; bh=coOKyd0rtvaMCxH/mKUGhnrdea7b8MWsrIPmIS/QuxI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fftd7LhkGm+RMmzRkGWHknXH10xDcr5JW+32yVRN7eeS6rc8/jfevENtzFVK8IC8VOCTF4g2Thx5JDEbxG5X09TbeWLHcZjF43guOh0F+4MZ9fiJsyFkLF1t/bGMgq+7GhVeNIfqQX3sTzedJ+8/Mx6rtTIlUEjmqPZSOCEt3ls= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=M4JVabPr; 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="M4JVabPr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3108F1F00899; Sun, 13 Sep 2026 17:17:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789319835; bh=hAIupWOiZk1Nz5VeipyYWCDtbEHKa9N+XsP7giaox3I=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=M4JVabPr5tlEOIeYIplnfYT0Jag0gmzQIJfF7+bhSEhJBzdlSiVJ5AIOObS7DEA2U Yi+Od02z8zbTQYmRUu0zi3Bg8x4hvohK8dJbPx95zCKSiMVQFiXTipmQginA7IFj9U mho/tBP8zswcf81rltqN8mN8kOKnPH3DAOHylzBiIHsmX5xo3MhvZx269rJ3SbHiYj DaGUef5aQCdfamdWKcth/YDiYtgDx4jo6puUf417+W/6KfzZxDGNJe15HDuDRAagK4 mOb/iNTAeGek/ZYHTo9WlI+uS4n/mmpFV9VguPlO6DceJBx0exlxB6ByhImS3OvgoU D/6IdS/x2OvMA== From: SJ Park To: Cc: SJ Park , stable@vger.kernel.org, Andrew Morton , Usama Arif , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH v2 2/8] mm/damon/sysfs-schemes: read sysfs_filter->sz_range only once Date: Sun, 13 Sep 2026 10:16:59 -0700 Message-ID: <20260913171706.103052-3-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260913171706.103052-1-sj@kernel.org> References: <20260913171706.103052-1-sj@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit DAMON sysfs interface reads the user-provided size range arguments for hugepage_size type DAMOS filter twice. Once for validation, and once again for assignments to the variable that will be passed to the core layer. If the user updates the arguments in parallel, an invalid size range could be passed to the core layer. Avoid it by doing the assignments first, and then validating the assigned variables before passing those to the core layer. User impact of the bug should be trivial. From the core layer's perspective, the invalid size range is not really invalid. It just works as having a weird size range. No critical issues such as a crash or a leak could happen. And sane users ain't do such parallel arguments update anyway. If they do, such racy behavior is arguably somewhat expected and deserved. That said, there is no reason to keep such races. Fixes: ea1f204ba29a ("mm/damon/sysfs-schemes: add files for setting damos_filter->sz_range") Cc: # 6.15.x Signed-off-by: SJ Park --- mm/damon/sysfs-schemes.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c index 3c1c1cb387fec..8c8ab82c8facc 100644 --- a/mm/damon/sysfs-schemes.c +++ b/mm/damon/sysfs-schemes.c @@ -2840,13 +2840,12 @@ static int damon_sysfs_add_scheme_filters(struct damos *scheme, } else if (filter->type == DAMOS_FILTER_TYPE_TARGET) { filter->target_idx = sysfs_filter->target_idx; } else if (filter->type == DAMOS_FILTER_TYPE_HUGEPAGE_SIZE) { - if (sysfs_filter->range_min > - sysfs_filter->range_max) { + filter->sz_range.min = sysfs_filter->range_min; + filter->sz_range.max = sysfs_filter->range_max; + if (filter->range_min > filter->range_max) { damos_destroy_filter(filter); return -EINVAL; } - filter->sz_range.min = sysfs_filter->range_min; - filter->sz_range.max = sysfs_filter->range_max; } else if (filter->type == DAMOS_FILTER_TYPE_PROBE_HITS_WSUM) { filter->range_min = sysfs_filter->range_min; filter->range_max = sysfs_filter->range_max; -- 2.47.3