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[2003:cb:c71b:7e00:9339:4017:7111:82d0]) by smtp.gmail.com with ESMTPSA id bh27-20020a05600c3d1b00b004141250b36fsm591517wmb.11.2024.03.22.14.18.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 22 Mar 2024 14:18:47 -0700 (PDT) Message-ID: <463612f2-5590-4fb3-8273-0d64c3fd3684@redhat.com> Date: Fri, 22 Mar 2024 22:18:46 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: BUG: unable to handle kernel paging request in fuse_copy_do To: Miklos Szeredi Cc: xingwei lee , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, samsun1006219@gmail.com, syzkaller-bugs@googlegroups.com, linux-mm , Mike Rapoport References: <620f68b0-4fe0-4e3e-856a-dedb4bcdf3a7@redhat.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: 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-Stat-Signature: r4oj5oqhbxd89s8418shj9u4su3xzwhb X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: D5FB818001D X-Rspam-User: X-HE-Tag: 1711142331-740049 X-HE-Meta: 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 qXWVsvOV tBH/DR63tvaZtBVs3WWsYBlbn+1HD5Jt3YN5QBC7sBISwLUcfA5qZqTRFQHtaeamEbtj9Z3wuIycvc2MctPJbLdRJhYSPyHhnWzc6pl5CvV6tia1da8/KUa6vKNH3hjp24tqfx7YLZV9iIGAPRPizqHUYoUJve8BGMxPxiZG5c4oBm+RnubogVDqrhtUIKBGRmHCNf5k0IL+80LSFUakudOUhiA== 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 22.03.24 22:13, Miklos Szeredi wrote: > On Fri, 22 Mar 2024 at 22:08, David Hildenbrand wrote: >> >> On 22.03.24 20:46, Miklos Szeredi wrote: >>> On Fri, 22 Mar 2024 at 16:41, David Hildenbrand wrote: >>> >>>> But at least the vmsplice() just seems to work. Which is weird, because >>>> GUP-fast should not apply (page not faulted in?) >>> >>> But it is faulted in, and that indeed seems to be the root cause. >> >> secretmem mmap() won't populate the page tables. So it's not faulted in yet. >> >> When we GUP via vmsplice, GUP-fast should not find it in the page tables >> and fallback to slow GUP. >> >> There, we seem to pass check_vma_flags(), trigger faultin_page() to >> fault it in, and then find it via follow_page_mask(). >> >> ... and I wonder how we manage to skip check_vma_flags(), or otherwise >> managed to GUP it. >> >> vmsplice() should, in theory, never succeed here. >> >> Weird :/ >> >>> Improved repro: >>> >>> #define _GNU_SOURCE >>> >>> #include >>> #include >>> #include >>> #include >>> #include >>> #include >>> >>> int main(void) >>> { >>> int fd1, fd2; >>> int pip[2]; >>> struct iovec iov; >>> char *addr; >>> int ret; >>> >>> fd1 = syscall(__NR_memfd_secret, 0); >>> addr = mmap(NULL, 4096, PROT_READ | PROT_WRITE, MAP_SHARED, fd1, 0); >>> ftruncate(fd1, 7); >>> addr[0] = 1; /* fault in page */ > > Here the page is faulted in and GUP-fast will find it. It's not in > the kernel page table, but it is in the user page table, which is what > matter for GUP. Trust me, I know the GUP code very well :P gup_pte_range -- GUP fast -- contains: if (unlikely(folio_is_secretmem(folio))) { gup_put_folio(folio, 1, flags); goto pte_unmap; } So we "should" be rejecting any secretmem folios and fallback to GUP slow. ... we don't check the same in gup_huge_pmd(), but we shouldn't ever see THP in secretmem code. -- Cheers, David / dhildenb