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 D58DF34A799; Thu, 30 Jul 2026 01:21:07 +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=1785374469; cv=none; b=AiygoZqecKsHgDjXLK/7nhQT5VZhUw7R7BFUw/jBV1t4ZZ30t/xDvbW8P5xpQa65R/3wfbKpj9j/DYEBvA/Bngb29tsfXZDoaNJq38fnWlzFbCU63tn7hhajBBuyoXFiDAu4kkrXy74Ii44e9LkitnmIo6rw1hLXzNtTHeF3d4Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785374469; c=relaxed/simple; bh=W8LAUQTKhzQlwMERF3J+9WW7bpnCbuCBBkt7eaqhAJc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sE/7PkqxKhZRWBBmr3/odPQnYzc/s+FNrN7a3i8T5i0+RhraL1PFw/O1OCTOnXwfmdBkdLyLhev0gorpRp3LnTo9WVctDJtoq+vsz57bJ8enmnm71NZTsrmr8FYkUY+txzhcUVpHzaXBV/7C/BUpQjn1KrF83aBT7+2LnJ1MdYk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=R1y/25vn; 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="R1y/25vn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4A2961F000E9; Thu, 30 Jul 2026 01:21:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785374467; bh=ZLjUXHvRJ7nDT2d1jnTK/WbFQsOhu3hY2whoDJ5YrZ4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=R1y/25vnoTCVqWMRXauDUI0wXaiYNs/APa8KJcqazrLZbOLlSpIiGK9bWPKSfWOXf g659WZetfWGql1wUBua5ZSVBaVE1L2jrZz5z8JqmMArz6KFhOjN7oBAqp7YSRyY66r Sy7/UU5alRTibeeTLAm1aVg/mT8bWXw5SiOjNe6hW0WWeiQZIKZPyOIINwTK1nOE5P NqwEtmYBHSQ7hIOCeiPihdIqdYa1/MtXnA+8iftdpCk7pccqcGjKZBC+o4blEOTyMb ca7gx906ci/mr15dbRuiRCSuGnArgWHDQByjZeOmWDAfRmAy7aq5fZsocSwOYM3ScS PotGtnbgE0nmw== From: SJ Park To: stable@vger.kernel.org Cc: damon@lists.linux.dev, SJ Park , Andrew Morton Subject: [PATCH 6.1.y] mm/damon/core: disallow overlapping input ranges for damon_set_regions() Date: Wed, 29 Jul 2026 18:20:58 -0700 Message-ID: <20260730012100.139829-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <2026072945-freezable-opossum-1bd2@gregkh> References: <2026072945-freezable-opossum-1bd2@gregkh> Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit damon_set_regions() assumes the input ranges are sorted by the address and don't overlap each other. Hence the assumption was initially to be explicitly validated. But commit 97d482f4592f ("mm/damon/sysfs: reuse damon_set_regions() for regions setting") has mistakenly removed the validation. This can make DAMON behave in unexpected ways. At the best, the monitoring results snapshot will just look weird since there will be overlapping regions. DAMOS will also work weirdly, applying the same action multiple times for overlapping regions, and make DAMOS quota weird. More seriously, depending on the setup and regions updates sequence, negative size regions can be made. It will trigger WARN_ONCE() if the kernel is built with CONFIG_DAMON_DEBUG_SANITY=y. Depending on the monitoring results, the negative size region can further trigger division by zero in damon_merge_two_regions(). Note that some of the consequences including the WARN_ONCE() and the divide by zero depend on commits that were introduced after the root cause commit 97d482f4592f ("mm/damon/sysfs: reuse damon_set_regions() for regions setting"). Fix the problems by checking the assumption and returning an error if the input ranges don't meet the assumption. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260703165610.92894-1-sj@kernel.org Link: https://lore.kernel.org/20260630041806.151124-1-sj@kernel.org [1] Fixes: 97d482f4592f ("mm/damon/sysfs: reuse damon_set_regions() for regions setting") Signed-off-by: SJ Park Cc: # 5.19.x Signed-off-by: Andrew Morton (cherry picked from commit 954157679ec34661c2e87e7eb796104a797c32db) Signed-off-by: SJ Park --- NOTE: This should be applied after https://lore.kernel.org/20260730010151.119009-1-sj@kernel.org mm/damon/core.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 0a0bb033f28a4..dd4eafe8b9611 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -210,12 +210,19 @@ int damon_set_regions(struct damon_target *t, struct damon_addr_range *ranges, { struct damon_region *r, *next; unsigned int i; + unsigned long last_end; int err; for (i = 0; i < nr_ranges; i++) { - if (ALIGN_DOWN(ranges[i].start, DAMON_MIN_REGION) >= - ALIGN(ranges[i].end, DAMON_MIN_REGION)) + unsigned long start, end; + + start = ALIGN_DOWN(ranges[i].start, DAMON_MIN_REGION); + end = ALIGN(ranges[i].end, DAMON_MIN_REGION); + if (start >= end) + return -EINVAL; + if (i > 0 && last_end > start) return -EINVAL; + last_end = end; } /* Remove regions which are not in the new ranges */ -- 2.47.3