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(p200300cbc712fa0038eb93adbe38d469.dip0.t-ipconnect.de. [2003:cb:c712:fa00:38eb:93ad:be38:d469]) by smtp.gmail.com with ESMTPSA id d2-20020a05600c34c200b004155387c08esm1768933wmq.27.2024.04.10.02.54.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 10 Apr 2024 02:54:12 -0700 (PDT) Message-ID: Date: Wed, 10 Apr 2024 11:54:11 +0200 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 5.4.y] x86/mm/pat: fix VM_PAT handling in COW mappings To: stable@vger.kernel.org Cc: Wupeng Ma , Ingo Molnar , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" References: <2024040847-departure-lining-fed7@gregkh> <20240410094908.191993-1-david@redhat.com> From: David Hildenbrand Content-Language: en-US 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: <20240410094908.191993-1-david@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10.04.24 11:49, David Hildenbrand wrote: > PAT handling won't do the right thing in COW mappings: the first PTE (or, > in fact, all PTEs) can be replaced during write faults to point at anon > folios. Reliably recovering the correct PFN and cachemode using > follow_phys() from PTEs will not work in COW mappings. > > Using follow_phys(), we might just get the address+protection of the anon > folio (which is very wrong), or fail on swap/nonswap entries, failing > follow_phys() and triggering a WARN_ON_ONCE() in untrack_pfn() and > track_pfn_copy(), not properly calling free_pfn_range(). > > In free_pfn_range(), we either wouldn't call memtype_free() or would call > it with the wrong range, possibly leaking memory. > > To fix that, let's update follow_phys() to refuse returning anon folios, > and fallback to using the stored PFN inside vma->vm_pgoff for COW mappings > if we run into that. > > We will now properly handle untrack_pfn() with COW mappings, where we > don't need the cachemode. We'll have to fail fork()->track_pfn_copy() if > the first page was replaced by an anon folio, though: we'd have to store > the cachemode in the VMA to make this work, likely growing the VMA size. > > For now, lets keep it simple and let track_pfn_copy() just fail in that > case: it would have failed in the past with swap/nonswap entries already, > and it would have done the wrong thing with anon folios. > > Simple reproducer to trigger the WARN_ON_ONCE() in untrack_pfn(): > > <--- C reproducer ---> > #include > #include > #include > #include > > int main(void) > { > struct io_uring_params p = {}; > int ring_fd; > size_t size; > char *map; > > ring_fd = io_uring_setup(1, &p); > if (ring_fd < 0) { > perror("io_uring_setup"); > return 1; > } > size = p.sq_off.array + p.sq_entries * sizeof(unsigned); > > /* Map the submission queue ring MAP_PRIVATE */ > map = mmap(0, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, > ring_fd, IORING_OFF_SQ_RING); > if (map == MAP_FAILED) { > perror("mmap"); > return 1; > } > > /* We have at least one page. Let's COW it. */ > *map = 0; > pause(); > return 0; > } > <--- C reproducer ---> > > On a system with 16 GiB RAM and swap configured: > # ./iouring & > # memhog 16G > # killall iouring > [ 301.552930] ------------[ cut here ]------------ > [ 301.553285] WARNING: CPU: 7 PID: 1402 at arch/x86/mm/pat/memtype.c:1060 untrack_pfn+0xf4/0x100 > [ 301.553989] Modules linked in: binfmt_misc nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_g > [ 301.558232] CPU: 7 PID: 1402 Comm: iouring Not tainted 6.7.5-100.fc38.x86_64 #1 > [ 301.558772] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebu4 > [ 301.559569] RIP: 0010:untrack_pfn+0xf4/0x100 > [ 301.559893] Code: 75 c4 eb cf 48 8b 43 10 8b a8 e8 00 00 00 3b 6b 28 74 b8 48 8b 7b 30 e8 ea 1a f7 000 > [ 301.561189] RSP: 0018:ffffba2c0377fab8 EFLAGS: 00010282 > [ 301.561590] RAX: 00000000ffffffea RBX: ffff9208c8ce9cc0 RCX: 000000010455e047 > [ 301.562105] RDX: 07fffffff0eb1e0a RSI: 0000000000000000 RDI: ffff9208c391d200 > [ 301.562628] RBP: 0000000000000000 R08: ffffba2c0377fab8 R09: 0000000000000000 > [ 301.563145] R10: ffff9208d2292d50 R11: 0000000000000002 R12: 00007fea890e0000 > [ 301.563669] R13: 0000000000000000 R14: ffffba2c0377fc08 R15: 0000000000000000 > [ 301.564186] FS: 0000000000000000(0000) GS:ffff920c2fbc0000(0000) knlGS:0000000000000000 > [ 301.564773] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 301.565197] CR2: 00007fea88ee8a20 CR3: 00000001033a8000 CR4: 0000000000750ef0 > [ 301.565725] PKRU: 55555554 > [ 301.565944] Call Trace: > [ 301.566148] > [ 301.566325] ? untrack_pfn+0xf4/0x100 > [ 301.566618] ? __warn+0x81/0x130 > [ 301.566876] ? untrack_pfn+0xf4/0x100 > [ 301.567163] ? report_bug+0x171/0x1a0 > [ 301.567466] ? handle_bug+0x3c/0x80 > [ 301.567743] ? exc_invalid_op+0x17/0x70 > [ 301.568038] ? asm_exc_invalid_op+0x1a/0x20 > [ 301.568363] ? untrack_pfn+0xf4/0x100 > [ 301.568660] ? untrack_pfn+0x65/0x100 > [ 301.568947] unmap_single_vma+0xa6/0xe0 > [ 301.569247] unmap_vmas+0xb5/0x190 > [ 301.569532] exit_mmap+0xec/0x340 > [ 301.569801] __mmput+0x3e/0x130 > [ 301.570051] do_exit+0x305/0xaf0 > ... > > Link: https://lkml.kernel.org/r/20240403212131.929421-3-david@redhat.com > Signed-off-by: David Hildenbrand > Reported-by: Wupeng Ma > Closes: https://lkml.kernel.org/r/20240227122814.3781907-1-mawupeng1@huawei.com > Fixes: b1a86e15dc03 ("x86, pat: remove the dependency on 'vm_pgoff' in track/untrack pfn vma routines") > Fixes: 5899329b1910 ("x86: PAT: implement track/untrack of pfnmap regions for x86 - v3") > Acked-by: Ingo Molnar > Cc: Dave Hansen > Cc: Andy Lutomirski > Cc: Peter Zijlstra > Cc: Thomas Gleixner > Cc: Borislav Petkov > Cc: "H. Peter Anvin" > Cc: > Signed-off-by: Andrew Morton > (cherry picked from commit 04c35ab3bdae7fefbd7c7a7355f29fa03a035221) > Signed-off-by: David Hildenbrand > --- Backport notes: (1) #include "../../mm/internal.h" to make it compile (2) vm_normal_folio -> vm_normal_page (3) follow_phys() is also used in generic_access_phys(), where we would now also reject anon pages. I don't think we care. -- Cheers, David / dhildenb