From nobody Wed Dec 17 11:13:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C9EC3C41513 for ; Thu, 19 Oct 2023 19:49:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346527AbjJSTtf (ORCPT ); Thu, 19 Oct 2023 15:49:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48238 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346466AbjJSTtd (ORCPT ); Thu, 19 Oct 2023 15:49:33 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1F745114; Thu, 19 Oct 2023 12:49:31 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 56F74C433C9; Thu, 19 Oct 2023 19:49:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697744970; bh=JqMVIy0mCbZQnCjtrYElDQM3Dsnc1xV+CtQNq7jTX4o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Oe6x2sCUCq4JfvkLqpDa4AQ+8p4t2drxdj8w0WFjYf1hxoNLFLp0vaQyeQ2Fc7j+J 2dPCch5ISN4TtP+cfgKjTVNCyIucKm3x3veg9XYIDq0nZ4dw4WO49I1KZAiEq6mQae DH+2HwS7+ej8MoOkb74v7OTx04+XRrJNyzlFwsK2oquSwLQYbewr/2rZMAZXriQUMv wP5LugNRndnmkqm9QCG3rgRkJd5JOb8OBuvRjAFkg4352A/MgAeCdCe0ZPxyuoju6h Ax7kASeHfQQLqMi3wUh8GQTMqxg65h0B92mS1Cxv7gGLnvwDjOk4281T9dP7jqX7BC 19G38VMbA3q2w== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH 1/5] mm/damon: implement a function for max nr_accesses safe calculation Date: Thu, 19 Oct 2023 19:49:20 +0000 Message-Id: <20231019194924.100347-2-sj@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231019194924.100347-1-sj@kernel.org> References: <20231019194924.100347-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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. Implement a function that handles the corner case. Note that this commit is not fixing the real issue since this is only introducing the safe function that will replaces the problematic divisions. The replacements will be made by followup commits, to make backporting on stable series easier. Fixes: 198f0f4c58b9 ("mm/damon/vaddr,paddr: support pageout prioritization") Cc: # 5.16.x Signed-off-by: SeongJae Park --- include/linux/damon.h | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/include/linux/damon.h b/include/linux/damon.h index 27b995c22497..ab2f17d9926b 100644 --- a/include/linux/damon.h +++ b/include/linux/damon.h @@ -681,6 +681,13 @@ static inline bool damon_target_has_pid(const struct d= amon_ctx *ctx) return ctx->ops.id =3D=3D DAMON_OPS_VADDR || ctx->ops.id =3D=3D DAMON_OPS= _FVADDR; } =20 +static inline unsigned int damon_max_nr_accesses(const struct damon_attrs = *attrs) +{ + /* {aggr,sample}_interval are unsigned long, hence could overflow */ + return min(attrs->aggr_interval / attrs->sample_interval, + (unsigned long)UINT_MAX); +} + =20 int damon_start(struct damon_ctx **ctxs, int nr_ctxs, bool exclusive); int damon_stop(struct damon_ctx **ctxs, int nr_ctxs); --=20 2.34.1 From nobody Wed Dec 17 11:13:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 70885CDB483 for ; Thu, 19 Oct 2023 19:49:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346550AbjJSTtj (ORCPT ); Thu, 19 Oct 2023 15:49:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48238 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346477AbjJSTtd (ORCPT ); Thu, 19 Oct 2023 15:49:33 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BD157CA; Thu, 19 Oct 2023 12:49:31 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 01A42C433CB; Thu, 19 Oct 2023 19:49:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697744971; bh=mCKYxJG6okaaxTlaAJiDWBfMeecgvhed2+n6U1OL4CI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DIpRll2dkGyuM/W1HY/OtCJ0rVq9bgajq0d8Ehg4VUWQ+lGFeTkQxBJjxh7927Hi9 uKHjKJjL5AQ5O6adkHXP684YQsUouzmOfAujbPozk8M3KHgXEKdIzLfxfiwsDdnxES boqYYS+F2Jcj+R1reI40WC6tfNeK0UiQnh1EFUyCvLYx6pyLPpEbJJGzu46FKY0IoY Fvl84swfOFhwCdZh9ZJzhO3w35UPmexJuKUte56Gfe7CwJJGB/j0sX3xffpEeDHNmN 6bP2glF0upzkOFUED5Q+3MUI51uFt0C67sqqVbo4OutJCy735/57FsWLl7U5qaOmjD A31VZ5YTiz7Jg== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH 2/5] mm/damon/core: avoid divide-by-zero during monitoring results update Date: Thu, 19 Oct 2023 19:49:21 +0000 Message-Id: <20231019194924.100347-3-sj@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231019194924.100347-1-sj@kernel.org> References: <20231019194924.100347-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When monitoring attributes are changed, DAMON updates access rate of the monitoring results accordingly. For that, it divides some values by the maximum nr_accesses. However, due to the type of the related variables, simple division-based calculation of the divisor can return zero. As a result, divide-by-zero is possible. Fix it by using damon_max_nr_accesses(), which handles the case. Fixes: 2f5bef5a590b ("mm/damon/core: update monitoring results for new moni= toring attributes") Cc: # 6.3.x Signed-off-by: SeongJae Park --- mm/damon/core.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 9f4f7c378cf3..e194c8075235 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -500,20 +500,14 @@ static unsigned int damon_age_for_new_attrs(unsigned = int age, static unsigned int damon_accesses_bp_to_nr_accesses( unsigned int accesses_bp, struct damon_attrs *attrs) { - unsigned int max_nr_accesses =3D - attrs->aggr_interval / attrs->sample_interval; - - return accesses_bp * max_nr_accesses / 10000; + return accesses_bp * damon_max_nr_accesses(attrs) / 10000; } =20 /* convert nr_accesses to access ratio in bp (per 10,000) */ static unsigned int damon_nr_accesses_to_accesses_bp( unsigned int nr_accesses, struct damon_attrs *attrs) { - unsigned int max_nr_accesses =3D - attrs->aggr_interval / attrs->sample_interval; - - return nr_accesses * 10000 / max_nr_accesses; + return nr_accesses * 10000 / damon_max_nr_accesses(attrs); } =20 static unsigned int damon_nr_accesses_for_new_attrs(unsigned int nr_access= es, --=20 2.34.1 From nobody Wed Dec 17 11:13:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0EDE1CDB482 for ; Thu, 19 Oct 2023 19:49:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346539AbjJSTth (ORCPT ); Thu, 19 Oct 2023 15:49:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48248 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346503AbjJSTte (ORCPT ); Thu, 19 Oct 2023 15:49:34 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6876311B; Thu, 19 Oct 2023 12:49:32 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9F662C433C8; Thu, 19 Oct 2023 19:49:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697744972; bh=mpZ0rzQnlOTIrrYJTnG5fwff80O37UKmtsf+aHi2YNo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OOgE1jz3lvMQfVP7TQZSOyc2aRshLkRxLJ6fzn2xEUat6kCKF9dHCXjOeqKgMRUkn JciYs/7W2GFKrLW8hHfKWb7PqfogevqMt/W8HSQOH0D+82UwlpAdZ4kkAZlACm/7Yd lD6zHpOrNamlwYL1JvFr3UqFSKsZRQ1C83Lu4MTrb569Z96fQBnp9j01s7w6xZ9Yus L+XY6w6H9dDlGykT60OConZ8snDx2JZCuR0vhKoLc74v3VmzIH7s8RZFN1aRYiH6OY +7tcNIopiD0jvwS2tVxbGdb8rayh09UhaZvj0Vg1VvBTo7/44eLy16O3BQ4MwcSBs7 FXMYu/8h+hHrw== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH 3/5] mm/damon/ops-common: avoid divide-by-zero during region hotness calculation Date: Thu, 19 Oct 2023 19:49:22 +0000 Message-Id: <20231019194924.100347-4-sj@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231019194924.100347-1-sj@kernel.org> References: <20231019194924.100347-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When calculating the hotness of each region for the under-quota regions prioritization, DAMON divides some values by the maximum nr_accesses. However, due to the type of the related variables, simple division-based calculation of the divisor can return zero. As a result, divide-by-zero is possible. Fix it by using damon_max_nr_accesses(), which handles the case. Fixes: 198f0f4c58b9 ("mm/damon/vaddr,paddr: support pageout prioritization") Cc: # 5.16.x Signed-off-by: SeongJae Park --- mm/damon/ops-common.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c index ac1c3fa80f98..d25d99cb5f2b 100644 --- a/mm/damon/ops-common.c +++ b/mm/damon/ops-common.c @@ -73,7 +73,6 @@ void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *= vma, unsigned long addr int damon_hot_score(struct damon_ctx *c, struct damon_region *r, struct damos *s) { - unsigned int max_nr_accesses; int freq_subscore; unsigned int age_in_sec; int age_in_log, age_subscore; @@ -81,8 +80,8 @@ int damon_hot_score(struct damon_ctx *c, struct damon_reg= ion *r, unsigned int age_weight =3D s->quota.weight_age; int hotness; =20 - max_nr_accesses =3D c->attrs.aggr_interval / c->attrs.sample_interval; - freq_subscore =3D r->nr_accesses * DAMON_MAX_SUBSCORE / max_nr_accesses; + freq_subscore =3D r->nr_accesses * DAMON_MAX_SUBSCORE / + damon_max_nr_accesses(&c->attrs); =20 age_in_sec =3D (unsigned long)r->age * c->attrs.aggr_interval / 1000000; for (age_in_log =3D 0; age_in_log < DAMON_MAX_AGE_IN_LOG && age_in_sec; --=20 2.34.1 From nobody Wed Dec 17 11:13:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EC6C4CDB483 for ; Thu, 19 Oct 2023 19:49:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346503AbjJSTtm (ORCPT ); Thu, 19 Oct 2023 15:49:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48258 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346506AbjJSTte (ORCPT ); Thu, 19 Oct 2023 15:49:34 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 13F37114; Thu, 19 Oct 2023 12:49:33 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 48C9FC433CA; Thu, 19 Oct 2023 19:49:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697744972; bh=JxnxpQi8Ul6nOhB30Sf8ttPU+Mbj0MwnPDqKZ/PALpM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Q/fE20KRyvJSGgRHegK3R+DBDTlM3NC4FaQxFC4fEJqSqwQHdqJucdhbh4cngKoMc 4Rii7MDRtomRT4L7TDzKSxzplwSoImsmMyfa3pLNK93O+F5ZWCTyb7IQdswuPcgchl 965fTzfU8pgybiLDqIrTq1WN72VSV27JSHJAoaMnrSmnzGcIde1GR1YtAwuXZXGr1W eg5GU5zj3caGORuA48hBOJgeswWu4AroqifVxo5HnxmR0uD99zC0Uig6ysPuqW9ijc ypsclOhxptVMU8Q7x6XKah1QWLn8ZPJiX2DEFntORfQiabj4NwIhRpZUTb/thUZHzA ufQlp0F+OjBaQ== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH 4/5] mm/damon/lru_sort: avoid divide-by-zero in hot threshold calculation Date: Thu, 19 Oct 2023 19:49:23 +0000 Message-Id: <20231019194924.100347-5-sj@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231019194924.100347-1-sj@kernel.org> References: <20231019194924.100347-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When calculating the hotness threshold for lru_prio scheme of DAMON_LRU_SORT, the module divides some values by the maximum nr_accesses. However, due to the type of the related variables, simple division-based calculation of the divisor can return zero. As a result, divide-by-zero is possible. Fix it by using damon_max_nr_accesses(), which handles the case. Fixes: 40e983cca927 ("mm/damon: introduce DAMON-based LRU-lists Sorting") Cc: # 6.0.x Signed-off-by: SeongJae Park --- mm/damon/lru_sort.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c index 3ecdcc029443..f2e5f9431892 100644 --- a/mm/damon/lru_sort.c +++ b/mm/damon/lru_sort.c @@ -195,9 +195,7 @@ static int damon_lru_sort_apply_parameters(void) if (err) return err; =20 - /* aggr_interval / sample_interval is the maximum nr_accesses */ - hot_thres =3D damon_lru_sort_mon_attrs.aggr_interval / - damon_lru_sort_mon_attrs.sample_interval * + hot_thres =3D damon_max_nr_accesses(&damon_lru_sort_mon_attrs) * hot_thres_access_freq / 1000; scheme =3D damon_lru_sort_new_hot_scheme(hot_thres); if (!scheme) --=20 2.34.1 From nobody Wed Dec 17 11:13:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 139ABC46CA1 for ; Thu, 19 Oct 2023 19:49:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346569AbjJSTto (ORCPT ); Thu, 19 Oct 2023 15:49:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48238 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346517AbjJSTte (ORCPT ); Thu, 19 Oct 2023 15:49:34 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6FB5711F for ; Thu, 19 Oct 2023 12:49:33 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E6BB7C433C9; Thu, 19 Oct 2023 19:49:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697744973; bh=A7qQGX2x61HuX9WngSjrxy/tMdxThwG7cO+vlCnt/oI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lNgSoOfsk3ij3VEBkFziLTTOeodtOyWouwKEqFx+/Vc1mq4dpwxhRKSnXoRwsoucb xmeYm9yqQYBthSax96jDtI9ODtXEb7yTCOZCjdebg76CWIbn9yQVDy2jFkZj8rYXd7 oNq9xzrIQ25Tmf5XiVN2Aee+jPubzu3B3kxz7bjVCA4KdCtkt8pFLhJZjYzNyONzZQ PkVOy9fqQoNU8ok3jV6I4nU555Th406ewtAd/tBdhmST6Bpzl33dF6VUag7JudpLqA tc87Na/V54yov3Z36qOUQBq0gpwPA3O3j6ZH+zXwVdSxO1X3vjDD/8mnwLNYKGgs1n qQNgxlmk5W1XA== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 5/5] mm/damon/core: avoid divide-by-zero from pseudo-moving window length calculation Date: Thu, 19 Oct 2023 19:49:24 +0000 Message-Id: <20231019194924.100347-6-sj@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231019194924.100347-1-sj@kernel.org> References: <20231019194924.100347-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When calculating the pseudo-moving access rate, DAMON divides some values by the maximum nr_accesses. However, due to the type of the related variables, simple division-based calculation of the divisor can return zero. As a result, divide-by-zero is possible. Fix it by using damon_max_nr_accesses(), which handles the case. Note that this is a fix for a commit that not in the mainline but mm tree. Fixes: ace30fb21af5 ("mm/damon/core: use pseudo-moving sum for nr_accesses_= bp") Signed-off-by: SeongJae Park --- Note that this is for a patch in mm-stable that not yet merged into the mainline. mm/damon/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index e194c8075235..aa2dc7087cd9 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -1665,7 +1665,7 @@ void damon_update_region_access_rate(struct damon_reg= ion *r, bool accessed, * aggr_interval, owing to validation of damon_set_attrs(). */ if (attrs->sample_interval) - len_window =3D attrs->aggr_interval / attrs->sample_interval; + len_window =3D damon_max_nr_accesses(attrs); r->nr_accesses_bp =3D damon_moving_sum(r->nr_accesses_bp, r->last_nr_accesses * 10000, len_window, accessed ? 10000 : 0); --=20 2.34.1