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[2003:cb:c739:600:d2fb:3a8a:9944:7910]) by smtp.gmail.com with ESMTPSA id d13-20020adfa34d000000b0034b1a91be72sm2187163wrb.14.2024.04.22.04.46.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 22 Apr 2024 04:46:21 -0700 (PDT) Message-ID: Date: Mon, 22 Apr 2024 13:46:20 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [syzbot] [mm?] WARNING in __page_table_check_ptes_set From: David Hildenbrand To: syzbot , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, pasha.tatashin@soleen.com, syzkaller-bugs@googlegroups.com References: <000000000000ca4df20616a0fe16@google.com> <71cf84d4-77d2-42d7-a649-b67497b171f6@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: X-Mimecast-Spam-Score: 1 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; 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>> >> mm/page_table_check.c:213 >>> Modules linked in: >>> CPU: 0 PID: 5084 Comm: syz-executor382 Not tainted 6.9.0-rc4-next-20240417-syzkaller #0 >>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024 >>> RIP: 0010:__page_table_check_pte mm/page_table_check.c:199 [inline] >>> RIP: 0010:__page_table_check_ptes_set+0x1db/0x420 mm/page_table_check.c:213 >>> Code: 48 8b 7c 24 40 48 c7 c6 80 19 46 8e e8 ee df 8e ff 41 83 fc 1d 74 18 41 83 fc 1a 75 1d e8 5d da 8e ff eb 10 e8 56 da 8e ff 90 <0f> 0b 90 eb 10 e8 4b da 8e ff 90 0f 0b 90 eb 05 e8 40 da 8e ff 48 >>> RSP: 0018:ffffc9000366f740 EFLAGS: 00010293 >>> RAX: ffffffff8207833a RBX: ffffc9000366f7c0 RCX: ffff888022af3c00 >>> RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000000 >>> RBP: ffffc9000366f830 R08: ffffffff820782af R09: 1ffffd40000a6a10 >>> R10: dffffc0000000000 R11: fffff940000a6a11 R12: 0000000000000000 >>> R13: 0000000014d42c67 R14: 0000000000000001 R15: 0000000000000000 >>> FS: 0000555567f79380(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000 >>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>> CR2: 000000000066c7e0 CR3: 0000000078cb0000 CR4: 00000000003506f0 >>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >>> Call Trace: >>> >>> page_table_check_ptes_set include/linux/page_table_check.h:74 [inline] >>> set_ptes include/linux/pgtable.h:267 [inline] >>> __ptep_modify_prot_commit include/linux/pgtable.h:1269 [inline] >>> ptep_modify_prot_commit include/linux/pgtable.h:1302 [inline] >>> change_pte_range mm/mprotect.c:194 [inline] >>> change_pmd_range mm/mprotect.c:424 [inline] >>> change_pud_range mm/mprotect.c:457 [inline] >>> change_p4d_range mm/mprotect.c:480 [inline] >>> change_protection_range mm/mprotect.c:508 [inline] >>> change_protection+0x2770/0x3cc0 mm/mprotect.c:542 >>> mprotect_fixup+0x740/0xa90 mm/mprotect.c:655 >>> do_mprotect_pkey+0x90d/0xe00 mm/mprotect.c:820 >>> __do_sys_mprotect mm/mprotect.c:841 [inline] >>> __se_sys_mprotect mm/mprotect.c:838 [inline] >>> __x64_sys_mprotect+0x80/0x90 mm/mprotect.c:838 >>> do_syscall_x64 arch/x86/entry/common.c:52 [inline] >>> do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83 >>> entry_SYSCALL_64_after_hwframe+0x77/0x7f >>> RIP: 0033:0x7f45514bf429 >>> Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 >>> RSP: 002b:00007ffe52191598 EFLAGS: 00000246 ORIG_RAX: 000000000000000a >>> RAX: ffffffffffffffda RBX: 00007ffe52191768 RCX: 00007f45514bf429 >>> RDX: 000000000000000f RSI: 0000000000004000 RDI: 0000000020ffc000 >>> RBP: 00007f4551532610 R08: 00007ffe52191768 R09: 00007ffe52191768 >>> R10: 00007ffe52191768 R11: 0000000000000246 R12: 0000000000000001 >>> R13: 00007ffe52191758 R14: 0000000000000001 R15: 0000000000000001 >>> >> >> Did we find a real issue that involves mprotect()? >> >> At least can_change_pte_writable() should always return "false" for >> userfaultfd_pte_wp(). >> >> Do we maybe have a uffd-wp PTE outside of a UFFD_WP VMA? >> >> Or was the PTE already writable and we only detect it now as we call >> mprotect()? (missed to detect it earlier?) > > Staring at the reproducer, we do > > > syscall(__NR_mmap, /*addr=*/0x1ffff000ul, /*len=*/0x1000ul, /*prot=*/0ul, > /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul, /*fd=*/-1, > /*offset=*/0ul); > syscall(__NR_mmap, /*addr=*/0x20000000ul, /*len=*/0x1000000ul, > /*prot=PROT_WRITE|PROT_READ|PROT_EXEC*/ 7ul, > /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul, /*fd=*/-1, > /*offset=*/0ul); > > -> Writable anonymous memmory > > syscall(__NR_mmap, /*addr=*/0x21000000ul, /*len=*/0x1000ul, /*prot=*/0ul, > /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul, /*fd=*/-1, > /*offset=*/0ul); > intptr_t res = 0; > res = syscall(__NR_userfaultfd, > /*flags=UFFD_USER_MODE_ONLY|O_NONBLOCK*/ 0x801ul); > if (res != -1) > r[0] = res; > *(uint64_t*)0x200004c0 = 0xaa; > *(uint64_t*)0x200004c8 = 0; > *(uint64_t*)0x200004d0 = 0; > syscall(__NR_ioctl, /*fd=*/r[0], /*cmd=*/0xc018aa3f, /*arg=*/0x200004c0ul); > > -> _UFFDIO_API handshake? > > syscall(__NR_mprotect, /*addr=*/0x20ffc000ul, /*len=*/0x3000ul, > /*prot=PROT_SEM|PROT_EXEC*/ 0xcul); > > -> Protect target range R/O. I assume: no page populated yet? > -> 3 pages starting at 0x20ffc000ul; > > *(uint64_t*)0x20000180 = 0x20ffc000; > *(uint64_t*)0x20000188 = 0x3000; > *(uint64_t*)0x20000190 = 3; > *(uint64_t*)0x20000198 = 0; > syscall(__NR_ioctl, /*fd=*/r[0], /*cmd=*/0xc020aa00, /*arg=*/0x20000180ul); > > -> _UFFDIO_REGISTER (aa00) > -> _range = 3 pages starting at 0x20ffc000ul > -> _mode = UFFDIO_REGISTER_MODE_WP | UFFDIO_REGISTER_MODE_MINOR > > *(uint64_t*)0x20000000 = 0x20ffd000; > *(uint64_t*)0x20000008 = 0x20ffb000; > *(uint64_t*)0x20000010 = 0x1000; > *(uint64_t*)0x20000018 = 3; > *(uint64_t*)0x20000020 = 0; > syscall(__NR_ioctl, /*fd=*/r[0], /*cmd=*/0xc028aa03, /*arg=*/0x20000000ul); > > -> _UFFDIO_COPY (aa03) > -> dst = 0x20ffd000 > -> src = 0x20ffb000 > -> len = 0x1000 (single page) > -> mode = UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP > > -> We are copying into the R/O range. src should be R/W and trigger a page fault > on access where we get a fresh page. > > *(uint16_t*)0x200000c0 = 1; > *(uint64_t*)0x200000c8 = 0x20000040; > *(uint16_t*)0x20000040 = 6; > *(uint8_t*)0x20000042 = 0; > *(uint8_t*)0x20000043 = 0; > *(uint32_t*)0x20000044 = 0x7fffffff; > res = syscall(__NR_seccomp, /*op=*/1ul, /*flags=*/0ul, /*arg=*/0x200000c0ul); > if (res != -1) > r[1] = res; > syscall(__NR_open_tree, /*dfd=*/-1, /*filename=*/0ul, /*flags=*/0ul); > > -> No idea what happens here and if it is relevant. If __NR_seccomp failed, we would > no set r[1]. > > syscall(__NR_close_range, /*fd=*/r[1], /*max_fd=*/-1, /*flags=*/0ul); > > -> Is that closing uffd as well, especially if __NR_seccomp failed? > > syscall(__NR_mprotect, /*addr=*/0x20ffc000ul, /*len=*/0x4000ul, > /*prot=PROT_SEM|PROT_WRITE|PROT_READ|PROT_EXEC*/ 0xful); > > -> Restore write permissions. This seems to fire the uffd-wp page table check I assume. I think the issue is that userfaultfd_release() will clear the VMA UFFD_WP flag, but it will not clear PTE uffd-wp bits. So we have leftover PTE uffd-wp bits at the time we wr-unprotect. I thought we removed that lazy handling, but looks like we didn't consider the "close uffd" case in: commit f369b07c861435bd812a9d14493f71b34132ed6f Author: Peter Xu Date: Thu Aug 11 16:13:40 2022 -0400 mm/uffd: reset write protection when unregister with wp-mode close should behave just like unregister. Simplified+readable reproducer: #define _GNU_SOURCE #include #include #include #include #include #include #include #include int main(void) { void *src = mmap(0, 4096, PROT_READ, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0); void *dst = mmap(0, 4096, PROT_READ, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0); struct uffdio_register uffdio_register = {}; struct uffdio_copy uffdio_copy = {}; struct uffdio_api uffdio_api = {}; int uffd; uffd = syscall(SYS_userfaultfd, O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY); uffdio_api.api = UFFD_API; ioctl(uffd, UFFDIO_API, &uffdio_api); uffdio_register.range.start = (uintptr_t)dst; uffdio_register.range.len = 4096; uffdio_register.mode = UFFDIO_REGISTER_MODE_WP; ioctl(uffd, UFFDIO_REGISTER, &uffdio_register); uffdio_copy.dst = (uintptr_t)dst; uffdio_copy.src = (uintptr_t)src; uffdio_copy.len = 4096; uffdio_copy.mode = UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP; ioctl(uffd, UFFDIO_COPY, &uffdio_copy); close(uffd); mprotect(dst, 4096, PROT_READ|PROT_WRITE); return 0; } -- Cheers, David / dhildenb