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[2003:cb:c715:8600:f05d:97b6:fb98:2bc1]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-367a29eab73sm1267268f8f.41.2024.07.04.12.05.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 04 Jul 2024 12:05:20 -0700 (PDT) Message-ID: Date: Thu, 4 Jul 2024 21:05:19 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] filemap: replace pte_offset_map() with pte_offset_map_nolock() To: Andrew Morton , Peng Zhang , linux-mm@kvack.org, linux-kernel@vger.kernel.org, willy@infradead.org, ying.huang@intel.com, fengwei.yin@intel.com, aneesh.kumar@linux.ibm.com, shy828301@gmail.com, hughd@google.com, wangkefeng.wang@huawei.com, sunnanyong@huawei.com References: <20240313012913.2395414-1-zhangpeng362@huawei.com> <20240625140643.bf4a1a19b0d534d802764610@linux-foundation.org> <20240704114039.4fd0739593cd0a96fe428496@linux-foundation.org> 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: <20240704114039.4fd0739593cd0a96fe428496@linux-foundation.org> 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-Queue-Id: 2B44840016 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: mshk94u9xroyq4o5byuh96xzkfijmcdi X-HE-Tag: 1720119925-284751 X-HE-Meta: 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 CAMnWpS5 R514hEyXKTTUXM6uSEj4bmhVZGwxsj+6ShN37P1TkOoh51hE/EKKPOoJMlhBteCoWDP5gZ3Q/X0WVsWp66TL1nQzAFLr3Qe0MYlcKeGK2db1NTHLRHclVMDu2VhShdlP1ig+acWjmSoPxcxiVY2yftYObCDfE0FMF9sdneAtb+qOxzIsf+vqQYqmBJdLC3ZcBuuEyCXE1LIJlrijHBE7LQ9ERjsTc6dVvZP/fuVnHqXfjeYjaEwKdqwHoKjF7LaaZ3mdgprgLFLyz9rWYURbhGtPhowmw6ZtWvhEZkFPCFio5kq3kj23Asluu+SAcPL3x32W9eowg0q5n1DFzxpBeK46e5fP9KCrUAoCM3cx5ZkqXV4HYWK8mHU/zPQNf0dGezug7qZXxl3bzCDcNKyTKAc9mENR214pdw1uy9WT7qfMPMNLxJRjWN70PELdGlfS+g+7mMUWqbapJliA= 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 04.07.24 20:40, Andrew Morton wrote: > On Tue, 25 Jun 2024 14:06:43 -0700 Andrew Morton wrote: > >> On Wed, 13 Mar 2024 09:29:13 +0800 Peng Zhang wrote: >> >>> From: ZhangPeng >>> >>> The vmf->ptl in filemap_fault_recheck_pte_none() is still set from >>> handle_pte_fault(). But at the same time, we did a pte_unmap(vmf->pte). >>> After a pte_unmap(vmf->pte) unmap and rcu_read_unlock(), the page table >>> may be racily changed and vmf->ptl maybe fails to protect the actual >>> page table. >>> Fix this by replacing pte_offset_map() with pte_offset_map_nolock(). >>> >>> ... >>> >>> --- a/mm/filemap.c >>> +++ b/mm/filemap.c >>> @@ -3207,7 +3207,8 @@ static vm_fault_t filemap_fault_recheck_pte_none(struct vm_fault *vmf) >>> if (!(vmf->flags & FAULT_FLAG_ORIG_PTE_VALID)) >>> return 0; >>> >>> - ptep = pte_offset_map(vmf->pmd, vmf->address); >>> + ptep = pte_offset_map_nolock(vma->vm_mm, vmf->pmd, vmf->address, >>> + &vmf->ptl); >>> if (unlikely(!ptep)) >>> return VM_FAULT_NOPAGE; >>> >> >> whoops, I'm still sitting on this because I didn't know whether we >> should backport it. >> >> And... guess what I say next. Can we please describe what are the >> userspace visible effects of the bug? >> > > Nobody? > > Oh well, I'll add cc:stable amd move this into mm-hotfixes. Yeah, we should better do that. IIRC, the PTL pointer might be stale (use after free?), although I cannot judge how often that should actually happen. -- Cheers, David / dhildenb