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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38dd4d826c6sm8823110f8f.69.2025.02.11.01.14.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 11 Feb 2025 01:15:00 -0800 (PST) Message-ID: <34bcf011-b4ac-479c-92ce-852623e73039@redhat.com> Date: Tue, 11 Feb 2025 10:14:58 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [REGRESSION] NULL pointer dereference on ARM (AT91SAM9G25) during compaction To: Qi Zheng , "Russell King (Oracle)" Cc: Ezra Buehler , linux-mm@kvack.org, Andrew Morton , "Mike Rapoport (Microsoft)" , Muchun Song , Vlastimil Babka , Ryan Roberts , "Vishal Moola (Oracle)" , Hugh Dickins , Matthew Wilcox , Peter Xu , Nicolas Ferre , Alexandre Belloni , Claudiu Beznea , open list , linux-arm-kernel@lists.infradead.org References: <5d50d714-197f-44c0-94e0-ff70ee51e866@bytedance.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: <5d50d714-197f-44c0-94e0-ff70ee51e866@bytedance.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: CNUi_u5Dv_TBSNBNWZJGwIqGS_51zlYP5Rk6tAnDWqk_1739265302 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-Rspamd-Queue-Id: 2984640011 X-Stat-Signature: umimdth7z1wd597m9skt1qk7ziifnf83 X-Rspamd-Server: rspam03 X-HE-Tag: 1739265304-158718 X-HE-Meta: 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 J41v1Pz3 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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 11.02.25 04:45, Qi Zheng wrote: > Hi Russell, > > On 2025/2/11 01:03, Russell King (Oracle) wrote: >> On Mon, Feb 10, 2025 at 05:49:38PM +0100, Ezra Buehler wrote: >>> When running vanilla Linux 6.13 or newer (6.14-rc2) on the >>> AT91SAM9G25-based GARDENA smart Gateway, we are seeing a NULL pointer >>> dereference resulting in a kernel panic. The culprit seems to be commit >>> fc9c45b71f43 ("arm: adjust_pte() usepte_offset_map_rw_nolock()"). >>> Reverting the commit apparently fixes the issue. >> >> The blamed commit is buggy: >> >> arch/arm/include/asm/tlbflush.h: >> #define update_mmu_cache(vma, addr, ptep) \ >> update_mmu_cache_range(NULL, vma, addr, ptep, 1) >> >> So vmf can be NULL. This didn't used to matter before this commit, >> because vmf was not used by ARM's update_mmu_cache_range(). However, >> the commit introduced a dereference of it, which now causes a NULL >> point dereference. >> >> Not sure what the correct solution is, but at a guess, both: >> >> if (ptl != vmf->ptl) >> >> need to become: >> >> if (!vmf || ptl != vmf->ptl) > > No, we can't do that, because without using split PTE locks, we would > use shared mm->page_table_lock, which would create a deadlock. Maybe we can simply special-case on CONFIG_SPLIT_PTE_PTLOCKS ? if (IS_ENABLED(CONFIG_SPLIT_PTE_PTLOCKS)) { ... } -- Cheers, David / dhildenb