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[2003:cb:c70c:de00:1200:8636:b63b:f43]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38254933d52sm5232332f8f.80.2024.11.21.05.50.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 21 Nov 2024 05:50:58 -0800 (PST) Message-ID: <25ead85f-2716-4362-8fb5-3422699e308c@redhat.com> Date: Thu, 21 Nov 2024 14:50:57 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/huge_memory: Fix to make vma_adjust_trans_huge() use find_vma() correctly From: David Hildenbrand To: Jeongjun Park , akpm@linux-foundation.org Cc: dave@stgolabs.net, willy@infradead.org, Liam.Howlett@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Lorenzo Stoakes References: <20241121124113.66166-1-aha310510@gmail.com> <26b82074-891f-4e26-b0a7-328ee2fa08d3@redhat.com> 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: <26b82074-891f-4e26-b0a7-328ee2fa08d3@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: Va1wQyCE7Pxk_QB39YB6LWjBiJ2pdKg01DhQlI5C9Wo_1732197060 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: rspam10 X-Stat-Signature: n5z8dbaqon5nkbfkwxpg7hoz8h6tfrps X-Rspamd-Queue-Id: 15DE940006 X-Rspam-User: X-HE-Tag: 1732196996-316465 X-HE-Meta: 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 4G3e/az7 3Dga24wwGjI0wCyGvk79e6aOBakR8mDD5YDkNroJLk7xc/VY9XmkEK9CjgssHxyfvyWV5zhbVYijHen1Yx2l81ihOcAWS1fP1AQTo4h2KkbcK3Em7eywxdhvmLk/4g/WP0JT86sb1JcDvpAhn9axoivVw9dH8sWyQt1iZbHaC0cUlnc+8xCxJRanLiCA1DmryY4YsZa3E91pqqyPKggLMaGqTP+9bOxvSAaRT7NKIRr/dAo/4VO9Om6xxRL2oaK4ta9i9Fi1UbsTPaTP+3f7b1utHMegOfcI9MYaK9fboWB5ZeDQYLsGa/ZhYmr2NSKQiuKyvRfRgUaAmV6vrN4l3Zs+fHD8YLwAguqIY9XUsgzkBbrve2Pw/DTkUvOhnNboTpTbbIX5vWHSW0vwX/wA4fcbfjhJFDnCoyDl5yrr25jRowrgIPndaOzfuO4wR6VtMwwQHvjZkBCdzmubSnSMAFZNy4g== 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 21.11.24 14:44, David Hildenbrand wrote: > On 21.11.24 13:41, Jeongjun Park wrote: >> vma_adjust_trans_huge() uses find_vma() to get the VMA, but find_vma() uses >> the returned pointer without any verification, even though it may return NULL. >> In this case, NULL pointer dereference may occur, so to prevent this, >> vma_adjust_trans_huge() should be fix to verify the return value of find_vma(). >> >> Cc: >> Fixes: 685405020b9f ("mm/khugepaged: stop using vma linked list") > > If that's an issue, wouldn't it have predated that commit? > > struct vm_area_struct *next = vma->vm_next; > unsigned long nstart = next->vm_start; > > Would have also assumed that there is a next VMA that can be > dereferenced, no? > And looking into the details, we only assume that there is a next VMA if we are explicitly told to by the caller of vma_adjust_trans_huge() using "adjust_next". There is only one such caller, vma_merge_existing_range()->commit_merge() where we set adj_start -> "adjust_next" where we seem to have a guarantee that there is a next VMA. So I don't think there is an issue here (although the code does look confusing ...). Not sure, though, if a if (WARN_ON_ONCE(!next)) return; would be reasonable. -- Cheers, David / dhildenb