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b=DzZfMQncqTIaP5p3UzNb7vrOecGw38WnRL2X5aQSu2cAD7rBl8MYqx+f+9yD504IE lCEWYu8sVr+IcnAZj+LMKRBiDa+BtqQYoOuh9C+4gO5J/I46AkegV2di1xdmguyOIa yPtF4lZeoWsWYFWOKwcslKnthVnVc7DqujgNV+lnJy2Lne727M5VddP61DfsXLfYnI tbKlXHxV/OW34zYzWGR1XpnoQghexizUv+OxenfaHlYLx+x+QF7pUmdtYW0a4S6Gsf nQ4MRas8P7JHnF9GT+JAIFUCOdbNSqDyoPXH6F1x6zvVbpDXQCzoC7HWGAd6YCtNqV dVJfoqjmnhXyw== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH 6.18.y 3/5] mm/damon/sysfs-schemes: read sysfs_filter->sz_range only once Reply-To: sashiko-reviews@lists.linux.dev To: "SJ Park" Cc: "Andrew Morton" , "Brendan Higgins" , "David Gow" , "Usama Arif" , damon@lists.linux.dev, linux-mm@kvack.org In-Reply-To: <20261108192221.114362-4-sj@kernel.org> References: <20261108192221.114362-1-sj@kernel.org> <20261108192221.114362-4-sj@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Sun, 08 Nov 2026 19:30:36 +0000 X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 94FE41C0004 X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Stat-Signature: wwhoq9dfar9rxci98hqp6dd5d94jk9do X-HE-Tag: 1794166238-782251 X-HE-Meta: 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 nR9MBkgH 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 X-Archived-By: Thank you for your contribution! Sashiko AI review found no new issues in this patch, but noticed 1 related pre-existing issue it does not introduce: - [High] mm/damon/sysfs: TOCTOU race in damos_sysfs_add_quota_score() [1] -- commit 244e62bfada7cc56b0025da40ea03dad6d9c6420 Author: SJ Park mm/damon/sysfs-schemes: read sysfs_filter->sz_range only once This commit copies sysfs_filter->sz_range into filter->sz_range before validating it in damon_sysfs_add_scheme_filters() so that a concurrent sysfs update cannot pass an unvalidated size range to the core layer. Link: https://lore.kernel.org/20260914142327.92510-3-sj@kernel.org > diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c > index 37e0a8bef4b1f..0f945ef043709 100644 > --- a/mm/damon/sysfs-schemes.c > +++ b/mm/damon/sysfs-schemes.c > @@ -2493,12 +2493,11 @@ static int damon_sysfs_add_scheme_filters(struct = damos *scheme, > } else if (filter->type =3D=3D DAMOS_FILTER_TYPE_TARGET) { > filter->target_idx =3D sysfs_filter->target_idx; > } else if (filter->type =3D=3D DAMOS_FILTER_TYPE_HUGEPAGE_SIZE) { > - if (sysfs_filter->sz_range.min > > - sysfs_filter->sz_range.max) { > + filter->sz_range =3D sysfs_filter->sz_range; > + if (filter->sz_range.min > filter->sz_range.max) { > damos_destroy_filter(filter); > return -EINVAL; > } > - filter->sz_range =3D sysfs_filter->sz_range; > } > =20 > damos_add_filter(scheme, filter); [Severity: High] This problem wasn't introduced by this patch, but can damos_sysfs_add_quota_score() just below hit a similar double-read race on sysfs_goal->target_value [1]? mm/damon/sysfs-schemes.c:damos_sysfs_add_quota_score() { ... if (!sysfs_goal->target_value) continue; goal =3D damos_new_quota_goal(sysfs_goal->metric, sysfs_goal->target_value); ... } target_value_store() updates sysfs_goal->target_value without holding damon_sysfs_lock: CPU0 CPU1 damos_sysfs_add_quota_score() if (!sysfs_goal->target_value) target_value_store() kstrtoul(..., &goal->target_value) damos_new_quota_goal(..., sysfs_goal->target_value) ... damos_quota_score() mult_frac(..., goal->target_value) <-- divide-by-zero If a concurrent write sets sysfs_goal->target_value to 0 between the check and the second read, damos_new_quota_goal() creates a goal with a zero target_value, which later causes a divide-by-zero in damos_quota_score(). sysfs_goal->metric is also read twice in damos_sysfs_add_quota_score(), so a concurrent metric_store() between damos_new_quota_goal() and the switch can leave goal->nid or goal->current_value uninitialized. [1] https://sashiko.dev/#/bug/linux-7f814c9a-986f-4103-a55a-ef9537dcf62b --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261108192221.1143= 62-1-sj@kernel.org?part=3D3