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=1793021438; b=paeVD0EUThyPRTr0NPickMpu3huYT1e/s02ei12Rc9BiyfOYfB7/PXh+4N3h+GmDGtHi bsvsIWbhq86OViZeeUHbdnR5Jhehw0ZTkjeRsoJuUmfRo1lAb/hjGwz9RbXOg+L41QlqK CNTWjyb7UynS6J68bMyYzJEuV2CXKOpRM9cPo4oSgwHFOPKAiEhJsFi9uvBd6uWFLj0y/ nFPLNJbuYQFexCilXEi2mhIHBA7Hnc0sCsyTCt5DJfD4XszsPUTs/X8qeAdXKPEJ2XhQ+ FDBaHZSmg4txkS6VeYbHZvO3Wzx5hvjGqWbATttcKKHsZOAz4yM3Mlq8TuHTUusBpfQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793021438; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=toIxbZaluxY/csBPcQI9DXYgAKoZ5TBqxydeOi+bj/c=; b=tLLCL+zxHJBOzVRDgpLx3Kg50kfMc3z220P6nwJ6zmqw5C63TGPB/scy/dqimhecl3d2 yv0UKTprDclLwHnHwciwcjC8BzW2mYvh0julI5Y5gcJxVcYQfqzC6pdhbmHcfpT8IgfaB qdXw5wTRwXDmzTChKVoHzxJIqHpuufUrixTnX7RHjwrGpsa0HLBvw7vQ32oBlPg0ROI6E c2RyG69uFtA6brkbK+TTqRnJyW3jOqtinmF9lSlDNOh5N7kz11W3rwed+fBPJ1WUw1MNF 8mXKOdQBQfU9O+qZG4gKerpq7XGwzILZC2ZwG4ciVifcEq0Vuc+No2qDf0daQQE2oeg== 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=mGVZ47wI; 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 8C40D606A31B; Mon, 26 Oct 2026 13:30:38 +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=mGVZ47wI Received: by smtp.kernel.org (Postfix) with ESMTPSA id 036271F01825; Mon, 26 Oct 2026 13:30:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793021438; bh=toIxbZaluxY/csBPcQI9DXYgAKoZ5TBqxydeOi+bj/c=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=mGVZ47wI25337aHc0NOtWv1yyF4Wr13lGlNU0XG3sGX8znCtezXzr6SETOrGIy4gV i5WKCyfjhnilMzrc6VZxQnvxoqHnZtR8dV3Cp5v5duGQMgSOHt3Bdii9a8O99M+4D8 OwPzFtmfewyHhjItkGYU1CeJhM7ZE4noVYUAb7zp8Yh6aUfVDep8hXGd7G4cCYaaH+ ZHAjy6jmkKFxeRJmQj7WqJTZFkxCymp2z9q3lQdhrk8G+VQBto3BJX8CL3JTHDQ7tO CdtL8rvP+tCLOF4CAcx5CMh9YpoNG3UoNLMk6c0qptiabQzLy8Rr0FjsbQWrlKRdiQ Wctnd8UfBfyBw== From: SJ Park To: Sasha Levin Cc: SJ Park , Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org Subject: Re: [RFC PATCH 7.3.y] mm/damon/core: error damos_commit_quota_goal() for zero target_value Date: Mon, 26 Oct 2026 06:30:30 -0700 Message-ID: <20261026133031.26195-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <2026-10-25-1-daily-reply-0011-damon-zero-target-value-decline@kernel.org> References: X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Sasha, On Sun, 25 Oct 2026 19:29:57 -0400 Sasha Levin wrote: > > Notes for stable kernel porting. The upstream commit doesn't have > > Fixes: and therefore not ported to stable kernels. It turned out it > > fixes commit 8b549a4fd3c5 ("mm/damon/sysfs-schemes: commit damos quota > > goals user input to DAMOS") which was merged into v6.8. The user impact > > is a race condition that can result in divide-by-zero. Hence backport. > > The older trees don't need this one. The callers in 7.2, 6.18 and 6.12 > already reject a zero target_value (7.2 also has 06befa61c427 > ("mm/damon/lru_sort: error out for >10000 active_mem_bp") and a16fd3ad9d89 > ("samples/damon/mtier: error out for zero quota goal target values")), That's true. DAMON_LRU_SORT and DAMON_SAMPLE_MTIER are patched to be safe from this issue. But DAMON sysfs interface can pass zero target_value under a race condition. > the > commit has no Fixes: or Cc: stable, I didn't know the race condition when I wrote the patch, so didn't add Fixes: or Cc: stable. > and it is patch 1/3 of a series whose > patches 2 and 3 remove those caller-side checks. I'm not sure if this really matters. So, I think we still need to add this patch to older kernels. Please let me know if I'm missing something. Thanks, SJ [...]