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[2003:cb:c707:7600:5c18:5a7d:c5b7:e7a9]) by smtp.gmail.com with ESMTPSA id bv20-20020a0560001f1400b0033d73e1505bsm10794183wrb.18.2024.02.27.00.46.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 27 Feb 2024 00:46:44 -0800 (PST) Message-ID: <056a92c5-0cf6-4f71-a93e-d8c43d4eed08@redhat.com> Date: Tue, 27 Feb 2024 09:46:43 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] mm/memory: Fix boundary check for next PFN in folio_pte_batch() To: Lance Yang Cc: akpm@linux-foundation.org, ryan.roberts@arm.com, 21cnbao@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240227070418.62292-1-ioworker0@gmail.com> <90471b2f-826e-4275-a9a3-ec673c3e6af8@redhat.com> <2aa8b0f0-4fd4-469a-ba72-82fe01d37f15@redhat.com> 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: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 62F0440008 X-Rspam-User: X-Stat-Signature: uso4pc3kxjuf4gjm7b9izi8g1i9p97t4 X-Rspamd-Server: rspam01 X-HE-Tag: 1709023608-517699 X-HE-Meta: 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 mK3Ny6fT gb/ciMSqKOvvoD8R939VCBu5QpHzEkm16evGelWf2+1IkkHtKQKu8jwv5KNIsS8lzS1FGVs83lJuB7LVm3usieuyEnF0dqb9khkzP+TjJaZiO10jcdx1angl44rgFhzZMcDMORCMIWsTy89L4Veq/XfUYtU5HEKo+mc8Pl7/R3zh240MCYASgQTM0QS4bzQWyRE7h/o01CH415pSzMPYd6OvaUg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, 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 27.02.24 09:45, Lance Yang wrote: > On Tue, Feb 27, 2024 at 4:33 PM David Hildenbrand wrote: >> >> On 27.02.24 09:23, Lance Yang wrote: >>> Hey David, >>> >>> Thanks for taking time to review! >>> >>> On Tue, Feb 27, 2024 at 3:30 PM David Hildenbrand wrote: >>>> >>>> On 27.02.24 08:04, Lance Yang wrote: >>>>> Previously, in folio_pte_batch(), only the upper boundary of the >>>>> folio was checked using '>=' for comparison. This led to >>>>> incorrect behavior when the next PFN exceeded the lower boundary >>>>> of the folio, especially in corner cases where the next PFN might >>>>> fall into a different folio. >>>> >>>> Which commit does this fix? >>>> >>>> The introducing commit (f8d937761d65c87e9987b88ea7beb7bddc333a0e) is >>>> already in mm-stable, so we would need a Fixes: tag. Unless, Ryan's >>>> changes introduced a problem. >>>> >>>> BUT >>>> >>>> I don't see what is broken. :) >>>> >>>> Can you please give an example/reproducer? >>> >>> For example1: >>> >>> PTE0 is present for large folio1. >>> PTE1 is present for large folio1. >>> PTE2 is present for large folio1. >>> PTE3 is present for large folio1. >>> >>> folio_nr_pages(folio1) is 4. >>> folio_nr_pages(folio2) is 4. >>> >>> pte = *start_ptep = PTE0; >>> max_nr = folio_nr_pages(folio2); >>> >>> If folio_pfn(folio1) < folio_pfn(folio2), >>> the return value of folio_pte_batch(folio2, start_ptep, pte, max_nr) >>> will be 4(Actually it should be 0). >>> >>> For example2: >>> >>> PTE0 is present for large folio2. >>> PTE1 is present for large folio1. >>> PTE2 is present for large folio1. >>> PTE3 is present for large folio1. >>> >>> folio_nr_pages(folio1) is 4. >>> folio_nr_pages(folio2) is 4. >>> >>> pte = *start_ptep = PTE0; >>> max_nr = folio_nr_pages(folio1); >>> >> >> In both cases, start_ptep does not map the folio. >> >> It's a BUG in your caller unless I am missing something important. > > Sorry, I understood. > > Thanks for your clarification! I'll post some kernel doc as reply to Barry's export patch to clarify that. -- Cheers, David / dhildenb