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[2003:cb:c74b:5700:5813:c94a:9d6a:eedd]) by smtp.gmail.com with ESMTPSA id m10-20020adffa0a000000b003392172fd60sm13650491wrr.51.2024.01.24.05.57.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 24 Jan 2024 05:57:14 -0800 (PST) Message-ID: <82c14904-fb73-4ded-a643-f4cffb5cdbe5@redhat.com> Date: Wed, 24 Jan 2024 14:57:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] mm/userfaultfd: UFFDIO_MOVE implementation should use ptep_get() To: Ryan Roberts , Andrew Morton , Suren Baghdasaryan , Andrea Arcangeli Cc: linux-mm@kvack.org References: <20240123141755.3836179-1-ryan.roberts@arm.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: <20240123141755.3836179-1-ryan.roberts@arm.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-Rspam-User: X-Stat-Signature: hp6zgqyjetgkryzexx96airericj6oxy X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 7F203180003 X-HE-Tag: 1706104638-933461 X-HE-Meta: U2FsdGVkX1/TE4TBKg3J46IptztFPRBWJP/MmUVnH95mOK6eBwvYpSQhjAcrrrErldpeAhzn3KFIA+kbYiX4FbbqE1Z8CnQhwBkYhzHuuCG0LdB1N7S/ijFqvEt4hsKrI2vzWUyFr/HlxkD756ZB85SzurseGVmJsPlVgmes3T2u6lgtFeV8LBq3YHMHTrhS0f8yXzEHSqUXcCdFUSlh2r6ZOwYDlgPOqwMtckzviGfOmrUq8un+HISfDEkca1s/ntWpvT+a3tTZZeDHF5Pv5efUvVgqDMoamCquTi3MBQu4iM6+gXhPuwBArDm8GPRaTYY69kRKon6CRojfxd/4/TrK5SRPCPCSo+yJRPZZ1R6Ke9V69zbTVdkMMCIcCYLknMbwNoA6Anj5J0qlLK+ug/B/0nDYIo2YgjDr0n0Ey5/1PSn0x5JMRsXcqirGV5Keb/GjlCtXeEl7PYeJj2sxPFvLW6elWGz1a344TToSJk278GIAqTlQD35bqLDAD3g5/FeOSOXRgr6NswyiOToBg+wsSPBJX+nmC20Ns8ZfjRl/krgFqGTWuMn1RWghGGFopJWY4G6SLy5WgVaBF1aulj0JCpWrOy8qyOWvUKF4xQOgnE7UotvHL4+lzM1R8y0ezB9kJhto4aRnTQF+JN67o94RKNpEKXyIg8jUzkRHQ9eJ8qNeIWR0+SneDBY5S8LQmJFrxvuCjCjUMneJREKSL/yJ2VWlmqquSxGyk+BCjOkzF4EXIGphLwJ37dnp2xiqmgXxooa9FjpUMnTvjjE8bshhXaBg5q2RqRuQ47VFHPufw1vc0DFR9xziqC7DQa096e7n9YMQ5EgxtWdOvl/24opjlvDWFxfWS31bL8mjbFJvHsone2qrBoMxOAc0THj1hRYmMxlHfTiJmsqaI0jA3wGM69Lw/VWfULECgJqvFLR6fhkwxZDhGyyecqy4kK1AThwK3SXAJlVRPWoVgBC UA2XNSt1 TDJtgsqeO0BYC+FsZ+Fhzxv5cgdo4kzBrAOyMX2qKk1hpISHtyFHDXpfUYcP149zlxdLFP4m3cL8GjyKKnRYnKpVp/4XViIi/qw0NsRpHa2O8jZ+aJnjJiszfiuwrS1APohIzXbZiht8xDbjUuvlLeNhu/LNsl8lJ4xeic1cs7C+40uxEFuCr3jFc/O9NAyS99W9ymIKEg8SADWqiia8gQQykhw== 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 23.01.24 15:17, Ryan Roberts wrote: > Commit c33c794828f2 ("mm: ptep_get() conversion") converted all > (non-arch) call sites to use ptep_get() instead of doing a direct > dereference of the pte. Full rationale can be found in that commit's > log. > > Since then, UFFDIO_MOVE has been implemented which does 7 direct pte > dereferences. Let's fix those up to use ptep_get(). > > Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI") > Signed-off-by: Ryan Roberts > --- > Hi All, > > This applies on top of v6.8-rc1. I'm hoping this can be merged into the > next rc. > > I've asserted in the past that there is no reliable automated mechanism > to catch these; I'm relying on a combination of Coccinelle (which throws > up a lot of false positives) and some compiler magic to force a compiler > error on dereference. But given the frequency with which new issues are > coming up, I'll add it to my todo list to try to find an automated > solution. If we'd use a distinct type for pte pointers that are only passed around (and not worked on), the compiler would bail out when doing such assignments. Like typedef struct { unsigned long pte; } pte_t; typedef struct { unsigned long pte; } pte2_t; pte_t pte = { 2 }; pte2_t pte2; pte2 = pte; -> "error: incompatible types when assigning to type 'pte2_t' from type 'pte_t'" pte_get() would do the conversion. ... but just thinking about it this would require a lot of work. -- Cheers, David / dhildenb