From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793807516; b=IbxejRpCvzkszqgOMKpNAIN7P7Pi5wl0hoT7FEeRiPsJUF7NeLNrilkEsb9t4EoJB06T GtADcZBidOJWUTnoNxh99qHx3p9kpkp6UVoq/LQkR9Uf6DldTLRNUQlDFx6QBMX6boob1 Dv2L9RcH+ElFgrg2CwESlhEPgrHaVUFZr30fEHmeVGDUhJqaYyw/k81HvYCIDURhtin2/ i7nopev5/rJ6Uh+cIdYszcZS7B7E/Y8kOxB8Keii6uSrHdBEwGsvBd9+Jt1idVSXZrqxp 0yFSAHS2G/PeVIuDdGQeV1MytLDThvV/tnd+cu86KB8sEJd/Xu3UsD6M/TCuIKFf0rA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793807516; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Type: Content-Transfer-Encoding; bh=0sBhfxVoPTNwyeJI8hydpBvqTMqtbq2SWkwYzUSeiS8=; b=Gwo43DjMaNLWf2w25GMMvH8sf40Q9JXY3Tsae2Ibln8F3jotHvbpoFWfjHgBGwb3GE+t Sl1lmcEBKvAqVeWfUG8ebbt/sMc2cpNOfdVLJxan+y0Q1m35wjlub4ObJ+CchSeDE+c+t 8GFlAobpdthwj3iuPkGkCufQc0rrwcnUfkUnc607YZ2YT12RccCeZaxsQgOBHwYpLIidp Cc7OYg5iswJ6RoaBoDZvhuXvtQSGvonqoyh/ZOERLQlx8R7VLYc/mm7EpkBQrVz0pnyd8 2132/ejF1mvRnDLE+zTZScKXb8UlflIC2udlzhJBVGBfnpON/E0kE0wAlYXTN6JuQZQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=gff6DAI3; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 07B91606A31B for ; Wed, 4 Nov 2026 15:51:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=gff6DAI3 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 62EDA1F000C1; Wed, 4 Nov 2026 15:51:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793807515; bh=0sBhfxVoPTNwyeJI8hydpBvqTMqtbq2SWkwYzUSeiS8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=gff6DAI3lDNr7WYHV7JCx2pC52NmJjHoPQgqc/VkOEq9fdWYQis5DMFvbCzY25Ctl U9pJMb5uIugekGGGmQ3CqC472HfaSwIVObDXyjL9k67p9BNeIdJykNPnKVRLgPhAGj 64DqMMdiDIS1KSrbjzumz9znjgaGIuvjMGFKiyHYJnvUCPFPelQvQoYh2VfrjgkjlO mZX8rmADzAohUe0sl9VFGRvIZYndscQmo8tvz+VrOFcpGpFza7QWqVWariHyD1k3Ga TEwnx6odKrb85JrWnBXBFWq7rdHEmiT+6il5ccSvbQZx/gaPMTHT1qIGwBprJEPpnf qbleMZyN3ddaA== From: SJ Park To: sashiko-bot@kernel.org Cc: SJ Park , "Andrew Morton" , damon@lists.linux.dev, linux-mm@kvack.org Subject: Re: [RFC PATCH 2/4] mm/damon/sysfs-schemes: support DAMOS_FILTER_TYPE_AGE_MS Date: Wed, 4 Nov 2026 07:51:47 -0800 Message-ID: <20261104155148.83931-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: X-Mailing-List: damon@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Wed, 04 Nov 2026 15:50:23 +0000 sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: > - [Medium] mm/damon: 32-bit overflow calculating age_ms in damos_filter_match() > -- > > commit 9c78f1b31239922167bf213c5406c37c05fd310f > Author: SJ Park > > mm/damon/sysfs-schemes: support DAMOS_FILTER_TYPE_AGE_MS > > This commit exposes DAMOS_FILTER_TYPE_AGE_MS to the DAMON sysfs interface > using the "age_ms" filter type keyword and the existing min and max sysfs > range files. > > > diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c > > index 637f1bd0c950b..230987efac3ac 100644 > > --- a/mm/damon/sysfs-schemes.c > > +++ b/mm/damon/sysfs-schemes.c > > [ ... ] > > > @@ -2875,6 +2879,7 @@ static int damon_sysfs_add_scheme_filters(struct damos *scheme, > > filter->sz_range.max = sysfs_filter->range_max; > > break; > > case DAMOS_FILTER_TYPE_PROBE_HITS_WSUM: > > + case DAMOS_FILTER_TYPE_AGE_MS: > > filter->range_min = sysfs_filter->range_min; > > filter->range_max = sysfs_filter->range_max; > > break; > > [Severity: Medium] > When userspace configures an age_ms filter with range_min and range_max via > damon_sysfs_add_scheme_filters() on a 32-bit system, can age_ms overflow in > damos_filter_match()? > > When kdamond evaluates the filter via > kdamond_apply_schemes()->damon_do_apply_schemes()->damos_apply_scheme()->damos_core_filter_out()->damos_filter_match(): > > mm/damon/core.c:damos_filter_match() { > ... > case DAMOS_FILTER_TYPE_AGE_MS: > age_ms = r->age * ctx->attrs.aggr_interval / USEC_PER_MSEC; > matched = filter->range_min <= age_ms && > age_ms <= filter->range_max; > break; > ... > } > > Here r->age is unsigned int and ctx->attrs.aggr_interval is unsigned long > (in microseconds). On 32-bit architectures, multiplying r->age by > ctx->attrs.aggr_interval is performed in 32-bit unsigned arithmetic before > dividing by USEC_PER_MSEC, which wraps around once a region's age exceeds > approximately 4,295 seconds (~71.6 minutes) even though the resulting > millisecond value fits in a 32-bit unsigned long. > > A similar 32-bit overflow on r->age * c->attrs.aggr_interval in > damon_hot_score() in mm/damon/ops-common.c was fixed in commit 0284dff76e87 > ("mm/damon/ops-common: fix age_in_sec overflow on 32-bit"). Should > damos_filter_match() use div_u64((u64)r->age * ctx->attrs.aggr_interval, > USEC_PER_MSEC) as well? I will fix [1] in the next version. [1] https://lore.kernel.org/20261104154746.83311-1-sj@kernel.org > > -- > Sashiko AI review ยท https://sashiko.dev/#/patchset/20261104153645.82945-1-sj@kernel.org?part=2 > Thanks, SJ