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[2003:cb:c729:9900:adb1:b447:d06e:820a]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42e96a56fd1sm160146565e9.48.2024.09.30.13.35.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Sep 2024 13:36:00 -0700 (PDT) Message-ID: Date: Mon, 30 Sep 2024 22:35:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] mm/huge_memory: check pmd_special() only after pmd_present() To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, syzbot+bf2c35fa302ebe3c7471@syzkaller.appspotmail.com, Peter Xu , "akpm@linux-foundation.org" References: <20240926154234.2247217-1-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: <20240926154234.2247217-1-david@redhat.com> 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-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 6699510000B X-Stat-Signature: piiim8kfdob483gq487j8z889qrhz8in X-HE-Tag: 1727728564-665215 X-HE-Meta: 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 v3+CfOQN 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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 26.09.24 17:42, David Hildenbrand wrote: > We should only check for pmd_special() after we made sure that we > have a present PMD. For example, if we have a migration PMD, > pmd_special() might indicate that we have a special PMD although we > really don't. > > This fixes confusing migration entries as PFN mappings, and not > doing what we are supposed to do in the "is_swap_pmd()" case further > down in the function -- including messing up COW, page table handling > and accounting. > > Reported-by: syzbot+bf2c35fa302ebe3c7471@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/lkml/66f15c8d.050a0220.c23dd.000f.GAE@google.com/ > Fixes: bc02afbd4d73 ("mm/fork: accept huge pfnmap entries") > Cc: Peter Xu > Signed-off-by: David Hildenbrand > --- > > I yet have to do more testing, but sending this out already. Testing looks good. Andrew please queue this, it's a rather unpleasent behavior if we fork() with a PMD migration entry that should be fixed upstream soonish :) (no idea how I could have missed CCing Andrew once more) -- Cheers, David / dhildenb