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[2003:d8:2f31:700:3851:c66a:b6b9:3490]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4532de8c64esm174224305e9.7.2025.06.17.01.53.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 17 Jun 2025 01:53:36 -0700 (PDT) Message-ID: Date: Tue, 17 Jun 2025 10:53:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] mm/madvise: initialize prev pointer in madvise_walk_vmas To: Lorenzo Stoakes Cc: Lance Yang , akpm@linux-foundation.org, 21cnbao@gmail.com, Liam.Howlett@oracle.com, vbabka@suse.cz, jannh@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Lance Yang References: <20250617020544.57305-1-lance.yang@linux.dev> <9e80cea5-fa78-46a2-b2bd-2f3846c24a34@lucifer.local> <8aa7932b-e30d-4025-8503-726e01bd7539@lucifer.local> 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: <8aa7932b-e30d-4025-8503-726e01bd7539@lucifer.local> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 79Gnl7n_QibX_U3bDc35vIidky-pflwEhUG4mZBW4PI_1750150418 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: rspam02 X-Rspamd-Queue-Id: 126CF140004 X-Stat-Signature: hxdt7kanywc6xytkaopwss14xkids6kc X-Rspam-User: X-HE-Tag: 1750150420-69920 X-HE-Meta: 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 79Z7Oj7X zW1HsIPch+Uqayha1nVrXDb5I+BGLG4ljkQN0u21hjZQWleu3i7Za94qc3M21hcsdniyyVaraU97JWmxcokW/voOMqFaFrlwmaAOS8Est4WeKyAIAMfUpky9C7UFBDNZV3IaXr7pveBHssjbnMeVFe32ry19Fri9d7/NUkEUDR0bvwajx0onMEMI1lBsr1I6Agg/iX1OG/lHWgE190kpny2fI8vNKghTSf2ylU+WZcp4seWOsHvTlpXaZQo+6r+IqW/r440bLgOoQ8li4jSSo/Z8QNRgA2AKGqMeyDhqP3hxBYDaxLns8MADqFbAHrtN8Phvdswz4SFosEBW8RlXiwWkLaIqEjxBvPQMtuVG6lFsrkdTKoFr7z6TH7283WQgKg6avNza7h78q+ANIZlpLg44X1/t4xc1ywLL7oT2Zmc/5fYf0ehqO/f2oANksGghMBfc5RoT1DO98XOZccDCcouzGjz+urpIYNB1Q 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 17.06.25 10:50, Lorenzo Stoakes wrote: > On Tue, Jun 17, 2025 at 10:38:07AM +0200, David Hildenbrand wrote: >>>>>> vma = vma_modify_flags_name(&vmi, *prev, ... >>>>>> >>>>>> We should use Fixes: then. >>>>> >>>>> So no we shouldn't... >>>>> >>>>>> >>>>>> >>>>>> Acked-by: David Hildenbrand >>>>> >>>>> Sure? :) >>>> >>>> Unless I am missing something important, yes :) >>> >>> This solution isn't correct as prev == NULL when prev != NULL is wholly >>> incorrect. >> >> I am not able to understand what you mean :) >> >> I assume you mean, that we reach a point down in the callchain, where "prev" >> is supposed to be set to something proper, but it would be "NULL". > > I mean if you tell merge code 'hey the previous VMA is NULL' (same thing as > saying 'hey this is the first VMA in the address space) and it isn't, bad things > will happen (TM). > >> >> That would indeed require a different fix. > > Yes this patch is wrong, sorry. > >> >> I wonder why we didn't trigger this case so far? > > It's because it only happens since Barry's per-VMA lock logic... > > if (madv_behavior && madv_behavior->lock_mode == MADVISE_VMA_READ_LOCK) { > vma = try_vma_read_lock(mm, madv_behavior, start, end); > if (vma) { > error = visit(vma, &prev, start, end, arg); > vma_end_read(vma); > return error; > } > } > > Otherwise, we look up the find_vma_prev(): > > vma = find_vma_prev(mm, start, &prev); > > In madvise_dontneed_free() we always set *prev = vma _first_. > > Let me suggest the better fix to Lance higher in thread so he sees :) > > Not sure if a fixes is valid here given this isn't mainline yet, more so this > should be squashed with barry's series? If it's not in mm-stable yet, it can still be squashed, yes. -- Cheers, David / dhildenb