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[2003:d8:2f25:900:2e1e:d717:2543:c4d6]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-459e58554f2sm123323195e9.12.2025.08.08.01.21.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 08 Aug 2025 01:21:58 -0700 (PDT) Message-ID: <864f2ef6-51bd-42f3-9988-16b5e94f05d9@redhat.com> Date: Fri, 8 Aug 2025 10:21:57 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/memory-failure: fix infinite UCE for VM_PFNMAP pfn To: Jinjiang Tu , Miaohe Lin Cc: wangkefeng.wang@huawei.com, nao.horiguchi@gmail.com, akpm@linux-foundation.org, xueshuai@linux.alibaba.com, ziy@nvidia.com, osalvador@suse.de, linux-mm@kvack.org References: <20250806020520.631203-1-tujinjiang@huawei.com> <1e63c37f-8eb2-865d-d3f4-9ef928f1a959@huawei.com> <35e24029-d58c-47e8-b5fe-e182f143ebff@huawei.com> <156267ef-f834-4bea-9dc0-c8ad32d066b0@huawei.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/g1oFAmgsLPQFCRvGjuMACgkQTd4Q 9wD/g1o0bxAAqYC7gTyGj5rZwvy1VesF6YoQncH0yI79lvXUYOX+Nngko4v4dTlOQvrd/vhb 02e9FtpA1CxgwdgIPFKIuXvdSyXAp0xXuIuRPQYbgNriQFkaBlHe9mSf8O09J3SCVa/5ezKM OLW/OONSV/Fr2VI1wxAYj3/Rb+U6rpzqIQ3Uh/5Rjmla6pTl7Z9/o1zKlVOX1SxVGSrlXhqt kwdbjdj/csSzoAbUF/duDuhyEl11/xStm/lBMzVuf3ZhV5SSgLAflLBo4l6mR5RolpPv5wad GpYS/hm7HsmEA0PBAPNb5DvZQ7vNaX23FlgylSXyv72UVsObHsu6pT4sfoxvJ5nJxvzGi69U s1uryvlAfS6E+D5ULrV35taTwSpcBAh0/RqRbV0mTc57vvAoXofBDcs3Z30IReFS34QSpjvl Hxbe7itHGuuhEVM1qmq2U72ezOQ7MzADbwCtn+yGeISQqeFn9QMAZVAkXsc9Wp0SW/WQKb76 FkSRalBZcc2vXM0VqhFVzTb6iNqYXqVKyuPKwhBunhTt6XnIfhpRgqveCPNIasSX05VQR6/a OBHZX3seTikp7A1z9iZIsdtJxB88dGkpeMj6qJ5RLzUsPUVPodEcz1B5aTEbYK6428H8MeLq NFPwmknOlDzQNC6RND8Ez7YEhzqvw7263MojcmmPcLelYbfOwU0EVcufkQEQAOfX3n0g0fZz 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+DWgUCaCwtJQUJG8aPFAAKCRBN3hD3AP+DWlDnD/4k2TW+HyOOOePVm23F5HOhNNd7nNv3 Vq2cLcW1DteHUdxMO0X+zqrKDHI5hgnE/E2QH9jyV8mB8l/ndElobciaJcbl1cM43vVzPIWn 01vW62oxUNtEvzLLxGLPTrnMxWdZgxr7ACCWKUnMGE2E8eca0cT2pnIJoQRz242xqe/nYxBB /BAK+dsxHIfcQzl88G83oaO7vb7s/cWMYRKOg+WIgp0MJ8DO2IU5JmUtyJB+V3YzzM4cMic3 bNn8nHjTWw/9+QQ5vg3TXHZ5XMu9mtfw2La3bHJ6AybL0DvEkdGxk6YHqJVEukciLMWDWqQQ RtbBhqcprgUxipNvdn9KwNpGciM+hNtM9kf9gt0fjv79l/FiSw6KbCPX9b636GzgNy0Ev2UV m00EtcpRXXMlEpbP4V947ufWVK2Mz7RFUfU4+ETDd1scMQDHzrXItryHLZWhopPI4Z+ps0rB CQHfSpl+wG4XbJJu1D8/Ww3FsO42TMFrNr2/cmqwuUZ0a0uxrpkNYrsGjkEu7a+9MheyTzcm vyU2knz5/stkTN2LKz5REqOe24oRnypjpAfaoxRYXs+F8wml519InWlwCra49IUSxD1hXPxO WBe5lqcozu9LpNDH/brVSzHCSb7vjNGvvSVESDuoiHK8gNlf0v+epy5WYd7CGAgODPvDShGN g3eXuA== Organization: Red Hat In-Reply-To: <156267ef-f834-4bea-9dc0-c8ad32d066b0@huawei.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: QiFvh8JMSbmP-lWRnGFt7Y3mdiNPEX924Z1GesbgLxw_1754641320 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: u8thhbdr1ymuwoxgpnq9e8kbw4r3x6wq X-Rspam-User: X-Rspamd-Queue-Id: 834C1160011 X-Rspamd-Server: rspam02 X-HE-Tag: 1754641330-661635 X-HE-Meta: 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 yPpBadD+ dr0WozU9E1tjBsrg65zeCYOxE6ahqmC6DwgJpJs2VRlkSh/WOT0dLvosOEFmHZ0C2ug0FkZIgH8Ezj2x6J5FkuVtsT2DHSd8OA95bhu2Qe4daGaFX0IlSH4/tlJDaedTM4fy97hk+Ewh9e7tH4d/j/uhrAEOfKC3XeV+XGl6+irG1G1OksY71dm7FRyFBSO51zA7l 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 07.08.25 13:13, Jinjiang Tu wrote: > > 在 2025/8/6 20:41, David Hildenbrand 写道: >> On 06.08.25 05:24, Jinjiang Tu wrote: >>> >>> 在 2025/8/6 11:05, Miaohe Lin 写道: >>>> On 2025/8/6 10:05, Jinjiang Tu wrote: >>>>> When memory_failure() is called for a already hwpoisoned pfn, >>>>> kill_accessing_process() will be called to kill current task. >>>>> However, if >>>> Thanks for your patch. >>>> >>>>> the vma of the accessing vaddr is VM_PFNMAP, walk_page_range() will >>>>> skip >>>>> the vma in walk_page_test() and return 0. >>>>> >>>>> Before commit aaf99ac2ceb7 ("mm/hwpoison: do not send SIGBUS to >>>>> processes >>>>> with recovered clean pages"), kill_accessing_process() will return >>>>> EFAULT. >>>> I'm not sure but pfn_to_online_page should return NULL for VM_PFNMAP >>>> pages? >>>> So memory_failure_dev_pagemap should handle these pages? >>> >>> We could call remap_pfn_range() for those pfns with struct page. >>> IIUC, VM_PFNMAP >>> means we should assume the pfn doesn't have struct page, but it can >>> have. >>> >>>>> For x86, the current task will be killed in kill_me_maybe(). >>>>> >>>>> However, after this commit, kill_accessing_process() simplies >>>>> return 0, >>>>> that means UCE is handled properly, but it doesn't actually. In >>>>> such case, >>>>> the user task will trigger UCE infinitely. >>>> Did you ever trigger this loop? >>> >>> Yes. Our test is as follow steps: >>> 1) create a user task allocates a clean anonymous page, wihout >>> accessing it. >>> 2) use einj to inject UCE for the page >>> 3) create task devmem to use /dev/mem to map the pfn and keep >>> accessing it. >> >> What is the use case for that? It sounds extremely questionable. >> > This case is only for test, and is strange indeed. > > But considering another case, a driver may map same RAM pfn to several processes with remap_pfn_range(). > If the first task triggers UCE when accessing the pfn, the task will be killed. But the other tasks couldn't be killed > and triggers UCE infinitely. Yes, the "anon page" example is confusing though. We really just want to test here if the PFN is mapped. And I would agree that your patch is correct in that case. For memory poisoning handling you really need a "struct page". struct-less memory is only handled in special ways for DAX (see pfn_to_online_page() logic in memory_failure()). So what you describe here really only works when a process uses remap_pfn_range() to VM_PFNMAP a struct-page-backed PFN. Likely your patch description should be: " mm/memory-failure: fix infinite UCE for VM_PFNMAP'ed page When memory_failure() is called for an already hardware poisoned page, kill_accessing_process() will conditionally send a SIGBUS to the current (triggering) process if it still maps the page. However, in case the page is not ordinarily mapped, but was mapped through remap_pfn_range(), kill_accessing_process() would not identify it as mapped even though hwpoison_pte_range() would be prepared to handle it, because walk_page_range() will skip VM_PFNMAP as default in walk_page_test(). walk_page_range() will return 0, assuming "not mapped" and the SIGBUS will be skipped. In this case, the user task will trigger UCE infinitely because it will not receive a SIGBUS on access and simply retry. Before commit aaf99ac2ceb7 ("mm/hwpoison: do not send SIGBUS to processes with recovered clean pages"), kill_accessing_process() would return EFAULT in that case, and on x86, the current task would be killed in kill_me_maybe(). Let's fix it by adding our custom .test_walk callback that will also process VM_PFNMAP VMAs. " -- Cheers, David / dhildenb