From mboxrd@z Thu Jan 1 00:00:00 1970 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5BF15E77188 for ; Wed, 8 Jan 2025 11:18:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B813D6B0095; Wed, 8 Jan 2025 06:18:48 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B2FF46B0096; Wed, 8 Jan 2025 06:18:48 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9A98D6B0098; Wed, 8 Jan 2025 06:18:48 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 7C8786B0095 for ; Wed, 8 Jan 2025 06:18:48 -0500 (EST) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 2C01744810 for ; Wed, 8 Jan 2025 11:18:48 +0000 (UTC) X-FDA: 82984037136.29.F46F350 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf24.hostedemail.com (Postfix) with ESMTP id A5E7818000E for ; Wed, 8 Jan 2025 11:18:45 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=A3+g8hsd; spf=pass (imf24.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1736335125; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=iP6DJLlFxBkXqREbDTn9k0FxT685l4fWlzaKHTa1mN4=; b=RM0N2/nO7BuMAVg5t6rfpswlJ8U1SRb62Pydft0mqepa00jTo1GKXRQUsu+yL6L1YLaEru h/nmdDksk2HjMgs+nLbrz3x8GCaIwUOYhkbp0/o4f+T6Ndqxxbr02SG9IbP/isM3l4OnXC uKhu8qmP8bv/roMHfJ+tIMWwjVo4z0Q= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=A3+g8hsd; spf=pass (imf24.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1736335125; a=rsa-sha256; cv=none; b=h79VTEcFQC5DgwYrNxwKo5YlhOoMmDwHJ0TUHATwsBIah0BiaDIPQSw29sXHvTCrM6bZXK zTv/6+4qK+dXoYz6+8ug5jzpVJ/VLhVSqp8bCJrE8+oKDhs3yclIpls/kEE4Ft4zfrc2EJ mPfurdnGe55zBmFUaJVXYjEonxIuS88= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1736335124; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=iP6DJLlFxBkXqREbDTn9k0FxT685l4fWlzaKHTa1mN4=; b=A3+g8hsdWF0etmbrATLFjPpitMWZbMXhgi3uMoAZH0fsSZNT0eHZP8Ipx0wqGLS0uQ84R4 BJBMHo/0pMB141bDVX9htf/aG+Dr8SZZaNWhL9MroI+4XO6mU+XbqKZl8KrDKJ6v2yS6uQ iVc5nak1aiLaXogORikUIc9koCmt//8= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-562-Dh5Tqq3DPMu-6f9VjR5fAQ-1; Wed, 08 Jan 2025 06:18:43 -0500 X-MC-Unique: Dh5Tqq3DPMu-6f9VjR5fAQ-1 X-Mimecast-MFC-AGG-ID: Dh5Tqq3DPMu-6f9VjR5fAQ Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-4361ecebc5bso48673025e9.1 for ; Wed, 08 Jan 2025 03:18:42 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1736335121; x=1736939921; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:to:subject:user-agent:mime-version :date:message-id:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=iP6DJLlFxBkXqREbDTn9k0FxT685l4fWlzaKHTa1mN4=; b=mBgbi2UN6fUUcz4wk3mEum5MKnZAj8Osb3wr7UFisbnM4B7CEtnGKRU9Lkg1ibIc4a MqOmcYskA3Vc/WzMBWT3R1mZGzvvs0aGFawag6MM+lIO0mAcu1wpgnkjhygue4d9XPX7 XXXN9e1YJQUfGqAFPzcBk+VuNLYKDlqaW/krlQCxqbj5FojvPf5PFnmOJDzHHRY2u0ZO NpPD74Fs5kfnE6STbLC1CQpsU/tAXYwKuuAdCJddeF+2y9NRX755cKiK3JkPIeMRMr7e iaRvQ7/C/bbeRuAv5RFSGo8FbR8cex6naxfVuGdETBJIHltbyp8TiYnz+3K7hF4NF4Uo sL9w== X-Forwarded-Encrypted: i=1; AJvYcCXdpWtTb4BTvGpIqJaOkHhROVW39lg1jek9ZqptUyV0kv8+MbOErL83i1pk+mS1UweJJUSkPjGckw==@kvack.org X-Gm-Message-State: AOJu0Yz+OQ+P1tRwtxdTAvTuezlMTnjznrmyfwGf1e9J14HkdIhGZibh auPTeSZu2YZNkTwjcJaWPNHQehGbaBriveEuekOcKq1fE7lfqbtUjQbWAMp7JtcsvVURNs3jwz8 6RvAsVQVn8rX2Jq18KkKH7UnN7JiYO5eSuDN87a0Kxe5XHT8b X-Gm-Gg: ASbGncvkYUISRAan4SVVxnypJxjkZS1EsCPkJwYJDB9XVp+/qyWz3c0vG9+w2YYYKVG J2WDDUJAVfKCT85An7afvKPGas5Uq1QDkI6WDaNUk/FIgdYbLVbApUabFxEo2AIDaEWT4UBucKg vtz3hWH8YFcX60E94gGShxQNxeG+wSzVKjmZSfnnuM/1X5LlvtDcIcRu57FnF1g6nBWKGnCfro3 zD5EieV2KyMu+qyRseUyA/nsjQ3QgFSkc8+ndEsbRh1htkAIJAfL/k2RoLP6MCKqvwZZsiWAEwK YZftGexVcoP6bBrBq9OSHBiFJY/58zfTVBxh8tnJYkXg9Xbp55WhnZ5cuCKTuzZQTLXAhFtrmM4 ysZijeA== X-Received: by 2002:a05:600c:4455:b0:434:fbcd:1382 with SMTP id 5b1f17b1804b1-436e26a80b6mr17290395e9.11.1736335121519; Wed, 08 Jan 2025 03:18:41 -0800 (PST) X-Google-Smtp-Source: AGHT+IFv7FVsRbp0xIlLDzPPJiv7vkWW8Ad5jA4CWxejyn9qdC8mY1Mm9bdPsdN00rRMO6T28SjnKg== X-Received: by 2002:a05:600c:4455:b0:434:fbcd:1382 with SMTP id 5b1f17b1804b1-436e26a80b6mr17290095e9.11.1736335121084; Wed, 08 Jan 2025 03:18:41 -0800 (PST) Received: from ?IPV6:2003:cb:c70d:3a00:d73c:6a8:ca9f:1df7? (p200300cbc70d3a00d73c06a8ca9f1df7.dip0.t-ipconnect.de. [2003:cb:c70d:3a00:d73c:6a8:ca9f:1df7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38a1c8b874asm52645893f8f.109.2025.01.08.03.18.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Jan 2025 03:18:39 -0800 (PST) Message-ID: Date: Wed, 8 Jan 2025 12:18:38 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: fix div by zero in bdi_ratio_from_pages To: Stefan Roesch , willy@infradead.org, zzqq0103.hey@gmail.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org References: <20250108014723.166637-1-shr@devkernel.io> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20250108014723.166637-1-shr@devkernel.io> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: dFI-GSwOGWJ5bpxSSWP2UFBkbnHwYJ6qEZuJKkHb4g4_1736335121 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: A5E7818000E X-Stat-Signature: ontwa9es7b3osbwibcdcmn8w7q34rxsn X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1736335125-357251 X-HE-Meta: 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 Hhrsx3yr 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 08.01.25 02:47, Stefan Roesch wrote: > During testing it has been detected, that it is possible to get div by > zero error in bdi_set_min_bytes. The error is caused by the function > bdi_ratio_from_pages(). bdi_ratio_from_pages() calls > global_dirty_limits. If the dirty threshold is 0, the div by zero is > raised. This can happen if the root user is setting: > > echo 0 > /proc/sys/vm/dirty_ratio > > The following is a test case: > > echo 0 > /proc/sys/vm/dirty_ratio > cd /sys/class/bdi/ > echo 1 > strict_limit > echo 8192 > min_bytes > > ==> error is raised. > > The problem is addressed by returning -EINVAL if dirty_ratio or > dirty_bytes is set to 0. > > Reported-by: cheung wall > Closes: https://lore.kernel.org/linux-mm/87pll35yd0.fsf@devkernel.io/T/#t > Signed-off-by: Stefan Roesch > > --- > Changes in V2: > - check for -EINVAL in bdi_set_min_bytes() > - check for -EINVAL in bdi_set_max_bytes() > --- > mm/page-writeback.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > index d213ead95675..fcc486e0d5c2 100644 > --- a/mm/page-writeback.c > +++ b/mm/page-writeback.c > @@ -692,6 +692,8 @@ static unsigned long bdi_ratio_from_pages(unsigned long pages) > unsigned long ratio; > > global_dirty_limits(&background_thresh, &dirty_thresh); > + if (!dirty_thresh) > + return -EINVAL; > ratio = div64_u64(pages * 100ULL * BDI_RATIO_SCALE, dirty_thresh); > > return ratio; > @@ -797,6 +799,8 @@ int bdi_set_min_bytes(struct backing_dev_info *bdi, u64 min_bytes) > return ret; > > min_ratio = bdi_ratio_from_pages(pages); > + if (min_ratio == -EINVAL) > + return -EINVAL; > return __bdi_set_min_ratio(bdi, min_ratio); > } > > @@ -816,6 +820,8 @@ int bdi_set_max_bytes(struct backing_dev_info *bdi, u64 max_bytes) > return ret; > > max_ratio = bdi_ratio_from_pages(pages); > + if (max_ratio == -EINVAL) > + return -EINVAL; I would have done it slightly differently, something like: diff --git a/mm/page-writeback.c b/mm/page-writeback.c index d213ead956750..4b02f18f7d01f 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -685,13 +685,15 @@ static int bdi_check_pages_limit(unsigned long pages) return 0; } -static unsigned long bdi_ratio_from_pages(unsigned long pages) +static long bdi_ratio_from_pages(unsigned long pages) { unsigned long background_thresh; unsigned long dirty_thresh; unsigned long ratio; global_dirty_limits(&background_thresh, &dirty_thresh); + if (!dirty_thresh) + return -EINVAL; ratio = div64_u64(pages * 100ULL * BDI_RATIO_SCALE, dirty_thresh); return ratio; @@ -790,13 +792,15 @@ int bdi_set_min_bytes(struct backing_dev_info *bdi, u64 min_bytes) { int ret; unsigned long pages = min_bytes >> PAGE_SHIFT; - unsigned long min_ratio; + long min_ratio; ret = bdi_check_pages_limit(pages); if (ret) return ret; min_ratio = bdi_ratio_from_pages(pages); + if (min_ratio < 0) + return min_ratio; return __bdi_set_min_ratio(bdi, min_ratio); } @@ -809,13 +813,15 @@ int bdi_set_max_bytes(struct backing_dev_info *bdi, u64 max_bytes) { int ret; unsigned long pages = max_bytes >> PAGE_SHIFT; - unsigned long max_ratio; + long max_ratio; ret = bdi_check_pages_limit(pages); if (ret) return ret; max_ratio = bdi_ratio_from_pages(pages); + if (min_ratio < 0) + return min_ratio; return __bdi_set_max_ratio(bdi, max_ratio); } -- Cheers, David / dhildenb