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[2003:cb:c71b:7e00:9339:4017:7111:82d0]) by smtp.gmail.com with ESMTPSA id f10-20020a05600c4e8a00b00412e5f32591sm622002wmq.28.2024.03.22.14.33.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 22 Mar 2024 14:33:46 -0700 (PDT) Message-ID: Date: Fri, 22 Mar 2024 22:33:45 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: BUG: unable to handle kernel paging request in fuse_copy_do From: David Hildenbrand 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> <463612f2-5590-4fb3-8273-0d64c3fd3684@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: <463612f2-5590-4fb3-8273-0d64c3fd3684@redhat.com> 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: BDD8220007 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: n66mcqwd3finwfi81pf43jo8zypesqjf X-HE-Tag: 1711143230-130279 X-HE-Meta: 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 fiMtIKzZ 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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 22.03.24 22:18, David Hildenbrand wrote: > 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. > Ehm: [ 29.441405] Secretmem fault: PFN: 1096177 [ 29.442092] GUP-fast: PFN: 1096177 ... is folio_is_secretmem() broken? ... is it something "obvious" like: diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h index 35f3a4a8ceb1e..6996f1f53f147 100644 --- a/include/linux/secretmem.h +++ b/include/linux/secretmem.h @@ -16,7 +16,7 @@ static inline bool folio_is_secretmem(struct folio *folio) * We know that secretmem pages are not compound and LRU so we can * save a couple of cycles here. */ - if (folio_test_large(folio) || !folio_test_lru(folio)) + if (folio_test_large(folio) || folio_test_lru(folio)) return false; mapping = (struct address_space *) -- Cheers, David / dhildenb