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 EB7FE41C71 for ; Thu, 2 Jul 2026 00:18:14 +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=1782951495; cv=none; b=g3/k+pjWMSIysL06C8x8at/7lcNg6IvMAvnngVF3/dNQVqrLz/IQT8tkpvtiGsfqrwdTGOD/sRlXiHjlTpjFecIT8pfGSLo/vor/2oe9tHt3dFai0KJAaHB7fbsiNUGS9zZP6vg2b6FfraetkrMLaa7K+OwXUA2NaW+655GWrr8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782951495; c=relaxed/simple; bh=RwyN5wF22Bktg5zvEFIlmq9JObMp4v2pj7knsh/0oqk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PdfrKbuRCR1Obe+DuEFRiAdJ7uBqKgA75DvDP4zKvi2Grl5yHSiolUZaHXueHvraBgcXfnlIK05DZU5xPD83tEOxPlIMyXl8E5E/keeTqB4tP4T3IS9WKT71OjZBNSIlaC749jW29kl3StPR3gskR9c2+d7ugwfPGVHSO3kHeQs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KVmN2Isw; 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="KVmN2Isw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 748861F00A3A; Thu, 2 Jul 2026 00:18:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782951494; bh=tB+k42O9GCXB5tQLC5pveS2zJySjrfqEesZZ2gloUW4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=KVmN2IswoMqO8cR7JCFav29Na6j9lPSCRhtmgVO2wFXGHCYhBB1CotLPU7S3hZThO G7XZBQInrpsVVs7TH4z1kiNhjyUikqeULzkTb5VqO/YNgPCD2WgrHlhtXPNaoILrHk K9i6dlwg8KHL/h7WRXYEp7DwEko2aqSZNFxq19nRLMXCOELPTrNBUWPz4wch5UjV7y BBw4uWI86OjNz7n9WnlFYZjWcjCoEsDIpl3A56ppkT/oTaP4ED6QC7EcJwOzrkR0ej I3mfzt9wj+N86Rg3HF0RyE54/72eBCKGyEugs8bTNqZSCkxzchTSW4QZEnjiass1Xm l2fCAQHPi3+jA== From: SJ Park To: sashiko-bot@kernel.org Cc: SJ Park , damon@lists.linux.dev Subject: Re: [RFC PATCH 7/8] mm/damon/core: remove start, end check in damon_set_region_system_rams() Date: Wed, 1 Jul 2026 17:18:06 -0700 Message-ID: <20260702001806.86969-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260701162221.370651F000E9@smtp.kernel.org> References: Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Wed, 01 Jul 2026 16:22:20 +0000 sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: > - [High] Removal of bounds validation permits inverted regions (start > end), leading to a massive integer underflow and guaranteed OOM kernel panic. > -- > > commit 03335779d391504c4265be49dedb155969cf1a7d > Author: SJ Park > > mm/damon/core: remove start, end check in damon_set_region_system_rams() > > This commit removes the explicit start > end validation in > damon_set_region_system_rams_default(), stating that damon_set_regions() > already performs a complete check. > > > diff --git a/mm/damon/core.c b/mm/damon/core.c > > index ace202f47dd7c..f491a76c98bfc 100644 > > --- a/mm/damon/core.c > > +++ b/mm/damon/core.c > > @@ -3794,9 +3794,6 @@ int damon_set_region_system_rams_default(struct damon_target *t, > > { > > struct damon_addr_range addr_range; > > > > - if (*start > *end) > > - return -EINVAL; > > - > [Severity: High] > The commit message states that the complete check is done inside > damon_set_regions(), but does damon_set_regions() actually validate that > start is less than or equal to end? > > Looking at damon_set_regions(), it appears to blindly create the region > with underflowed sizes if start > end: > > mm/damon/core.c:damon_set_regions() { > ... > r = damon_new_region( > ALIGN_DOWN(ranges[i].start, min_region_sz), > ALIGN(ranges[i].end, min_region_sz)); > ... > } > > If an inverted region (e.g., [4096, 0)) is passed in, could this lead to a > massive integer underflow? The size of the region would underflow to roughly > ULONG_MAX. > > Later in damon_apply_min_nr_regions(), this underflow seems to translate > into an effectively infinite loop: > > mm/damon/core.c:damon_apply_min_nr_regions() { > ... > while (damon_sz_region(r) > max_region_sz) { > damon_split_region_at(t, r, max_region_sz); > r = damon_next_region(r); > } > ... > } > > Could this loop exhaust system memory by attempting to allocate quadrillions > of regions and cause an OOM kernel panic? My previous reply [1] should be applied here. [1] https://lore.kernel.org/20260702001650.86841-1-sj@kernel.org Thanks, SJ [...]