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(p200300cbc7309700d653fb1975e5ab5c.dip0.t-ipconnect.de. [2003:cb:c730:9700:d653:fb19:75e5:ab5c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4313f56a6a3sm19822505e9.20.2024.10.15.07.40.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 15 Oct 2024 07:40:48 -0700 (PDT) Message-ID: Date: Tue, 15 Oct 2024 16:40:47 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] mm/pagewalk: fix usage of pmd_leaf()/pud_leaf() without present check To: "Kirill A. Shutemov" Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzbot+7d917f67c05066cec295@syzkaller.appspotmail.com, Andrew Morton , Jann Horn References: <20241015111236.1290921-1-david@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: 7bit X-Rspamd-Queue-Id: 0D26710000C X-Stat-Signature: q913h3d5yas8zbugufu8ni9d49487knm X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1729003243-672446 X-HE-Meta: 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 IizvDsoA 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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 15.10.24 16:32, Kirill A. Shutemov wrote: > On Tue, Oct 15, 2024 at 01:12:36PM +0200, David Hildenbrand wrote: >> pmd_leaf()/pud_leaf() only implies a pmd_present()/pud_present() check on >> some architectures. > > Should we clarify what behaviour we actually want from arch code? We probably should document somewhere that things like pmd_special(), pmd_leaf() ... should only be used when we know that the PMD is present. I wonder if we should even add ways to detect mis-use Jann also raised that recently in a private message, that it is rather unclear (well, and repeatedly leads to issues) when pmd_leaf() is valid to be called. Thanks! -- Cheers, David / dhildenb