From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 99C3F199941 for ; Mon, 23 Sep 2024 15:56:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727107010; cv=none; b=rd7WNTqWEyq+KqtHI8sGup33QBLcFAXYE4QYImcockXh5I8zqrRJq5bVJA61oE/cq5SXD6oDFKhraxkVMwoa4ViUlEDlOYor8rVJbbUi1XmWBCTVhlYbMCKkWBpqleKkC0evXhyP1OnF8XryhvTrf3xksMc6kP3MctXOQbdBBzw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727107010; c=relaxed/simple; bh=Sfcv3UiGe4fFEkLKPP5hazoawbszqENOM95UKgdF2ao=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=f4L53oa2Y7PRFXOHUcojhvJi1FuIENuSCge2M1MQ1KBwtpolIYz4YnL16nQ3PZtedcXS9x33mfnebFyPlUWnR/ILEmslTq8iB3y0IC2r3BGMd8F0ij7J0DWE3Wei+Xc2is1D3JfqqCFjIR5lN5gnRsb1fXKD0odBPqXv5f3u0nk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=BmpfOD5H; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="BmpfOD5H" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1727107007; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=iP3SkhF549Gc6brUSlweb2Vjw8EwOroSOBVuS2ghez0=; b=BmpfOD5HdMKNn6O9wYlTd+IMvBvsFnlH+rPV0dD9E3zsZqtB//BzhZjXs+POPWdf0NAntF bdDdd11lAecQ3WQzdaFqaLSqkAW+d5ZVi11nUMViKrHZVBi8CxxbJmEpY7jo/3CSFE0swu CqgV9Gvkn9sEellkBTfXdlCj6iLDgxM= Received: from mail-lj1-f197.google.com (mail-lj1-f197.google.com [209.85.208.197]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-190-wUOKuxofO2y9Gj_37n9OGg-1; Mon, 23 Sep 2024 11:56:45 -0400 X-MC-Unique: wUOKuxofO2y9Gj_37n9OGg-1 Received: by mail-lj1-f197.google.com with SMTP id 38308e7fff4ca-2f761cfa667so30425891fa.3 for ; Mon, 23 Sep 2024 08:56:45 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1727107004; x=1727711804; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=iP3SkhF549Gc6brUSlweb2Vjw8EwOroSOBVuS2ghez0=; b=HEKeMHof+W2Mt+6Td/cnQ7HjyQpZ/jwe5vp6WEM3YJGQ+02NHDJci5hpxssoqTiTyc XlESnigxmKS+3Ouv0sVZHd6GzUIE/CYt8r/zoJPDCh9k60ceqhYuAjN/wnS6WDo5SGeg VBMZ/ysDhy+61NT4nVx78ebwaYEjnDsbfo3ewnWuK/LSNFbfFJrxMDrG8GhWLGXsmg6G aNY+XZzD0+rU1UpDamQNWLhrZioEPhzp0pMZtklwvOA0PU9wXH003HWHb4fiixG/InQN 78LQDnB1uwEBcbnOuzaTH9x82vF/RZCxWnT/N4XOOOFv1r55GuiKYI5nHY6ExpIXEa0E oPTw== X-Forwarded-Encrypted: i=1; AJvYcCXPOaoOCylEwkEU4QT/iL2toAneg+Rxuq4m4sEbjya52U1RBLFSokwa8dafEjeDndl9hZ17U3V/0BfhNuA=@vger.kernel.org X-Gm-Message-State: AOJu0YzOZ1vEOSjxm12V4J6I/EQRAGpAcLza6P3udStkgDAmMRqCXpvc JPxOvVQJH/BtbjziCfEUbmC8AmmrtiCaotdql1qcs1GfZ6S8LZPUPypACMXjvHGz5dEe9KD18ne e/y4QSfk9S8AMUALQaeWs8LlmIuXqi+/irrYJpNvxCEV/qaNGHSavz+BM19s27Q== X-Received: by 2002:a2e:809:0:b0:2f7:4c9d:7a83 with SMTP id 38308e7fff4ca-2f7cc5baef2mr48377151fa.40.1727107004077; Mon, 23 Sep 2024 08:56:44 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFM0cX/xCUpbnPcURk/407mJfEncclVpDoCWCgm3Go/koit2Hybq9kArBgHN3IpRpvUi0ILDg== X-Received: by 2002:a2e:809:0:b0:2f7:4c9d:7a83 with SMTP id 38308e7fff4ca-2f7cc5baef2mr48376981fa.40.1727107003532; Mon, 23 Sep 2024 08:56:43 -0700 (PDT) Received: from [10.5.48.152] (90-181-218-29.rco.o2.cz. [90.181.218.29]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5c42bb5f4f1sm10472622a12.53.2024.09.23.08.56.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Sep 2024 08:56:42 -0700 (PDT) Message-ID: <31e90b74-8bd1-4bfe-9384-8d479735d2be@redhat.com> Date: Mon, 23 Sep 2024 17:56:40 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: migrate: fix data-race in migrate_folio_unmap() To: Jeongjun Park , akpm@linux-foundation.org Cc: wangkefeng.wang@huawei.com, ziy@nvidia.com, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, syzbot References: <20240922151708.33949-1-aha310510@gmail.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: <20240922151708.33949-1-aha310510@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 22.09.24 17:17, Jeongjun Park wrote: > I found a report from syzbot [1] > > When __folio_test_movable() is called in migrate_folio_unmap() to read > folio->mapping, a data race occurs because the folio is read without > protecting it with folio_lock. > > This can cause unintended behavior because folio->mapping is initialized > to a NULL value. Therefore, I think it is appropriate to call > __folio_test_movable() under the protection of folio_lock to prevent > data-race. > We hold a folio reference, would we really see PAGE_MAPPING_MOVABLE flip? Hmm Even a racing __ClearPageMovable() would still leave PAGE_MAPPING_MOVABLE set. > [1] > > ================================================================== > BUG: KCSAN: data-race in __filemap_remove_folio / migrate_pages_batch > > write to 0xffffea0004b81dd8 of 8 bytes by task 6348 on cpu 0: > page_cache_delete mm/filemap.c:153 [inline] > __filemap_remove_folio+0x1ac/0x2c0 mm/filemap.c:233 > filemap_remove_folio+0x6b/0x1f0 mm/filemap.c:265 > truncate_inode_folio+0x42/0x50 mm/truncate.c:178 > shmem_undo_range+0x25b/0xa70 mm/shmem.c:1028 > shmem_truncate_range mm/shmem.c:1144 [inline] > shmem_evict_inode+0x14d/0x530 mm/shmem.c:1272 > evict+0x2f0/0x580 fs/inode.c:731 > iput_final fs/inode.c:1883 [inline] > iput+0x42a/0x5b0 fs/inode.c:1909 > dentry_unlink_inode+0x24f/0x260 fs/dcache.c:412 > __dentry_kill+0x18b/0x4c0 fs/dcache.c:615 > dput+0x5c/0xd0 fs/dcache.c:857 > __fput+0x3fb/0x6d0 fs/file_table.c:439 > ____fput+0x1c/0x30 fs/file_table.c:459 > task_work_run+0x13a/0x1a0 kernel/task_work.c:228 > resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] > exit_to_user_mode_loop kernel/entry/common.c:114 [inline] > exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline] > __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] > syscall_exit_to_user_mode+0xbe/0x130 kernel/entry/common.c:218 > do_syscall_64+0xd6/0x1c0 arch/x86/entry/common.c:89 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > read to 0xffffea0004b81dd8 of 8 bytes by task 6342 on cpu 1: > __folio_test_movable include/linux/page-flags.h:699 [inline] > migrate_folio_unmap mm/migrate.c:1199 [inline] > migrate_pages_batch+0x24c/0x1940 mm/migrate.c:1797 > migrate_pages_sync mm/migrate.c:1963 [inline] > migrate_pages+0xff1/0x1820 mm/migrate.c:2072 > do_mbind mm/mempolicy.c:1390 [inline] > kernel_mbind mm/mempolicy.c:1533 [inline] > __do_sys_mbind mm/mempolicy.c:1607 [inline] > __se_sys_mbind+0xf76/0x1160 mm/mempolicy.c:1603 > __x64_sys_mbind+0x78/0x90 mm/mempolicy.c:1603 > x64_sys_call+0x2b4d/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:238 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > value changed: 0xffff888127601078 -> 0x0000000000000000 Note that this doesn't flip PAGE_MAPPING_MOVABLE, just some unrelated bits. > > Reported-by: syzbot > Cc: stable@vger.kernel.org > Fixes: 7e2a5e5ab217 ("mm: migrate: use __folio_test_movable()") > Signed-off-by: Jeongjun Park > --- > mm/migrate.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 923ea80ba744..e62dac12406b 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1118,7 +1118,7 @@ static int migrate_folio_unmap(new_folio_t get_new_folio, > int rc = -EAGAIN; > int old_page_state = 0; > struct anon_vma *anon_vma = NULL; > - bool is_lru = !__folio_test_movable(src); > + bool is_lru; > bool locked = false; > bool dst_locked = false; > > @@ -1172,6 +1172,7 @@ static int migrate_folio_unmap(new_folio_t get_new_folio, > locked = true; > if (folio_test_mlocked(src)) > old_page_state |= PAGE_WAS_MLOCKED; > + is_lru = !__folio_test_movable(src); Looks straight forward, though Acked-by: David Hildenbrand -- Cheers, David / dhildenb