From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 16DCD1AF0B0 for ; Tue, 15 Oct 2024 13:13:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728998000; cv=none; b=SYJMEmO4HKiAviJv2wMz5NhCdxh51wyMVonZ/fg5imKqUyiruR9O4w316sCvY3xafxFIvbpfx535YsU2xQb7tqbedWWIDmyk/h5eXKyydTBzn81W8bE7GIexYe+YRe02dCkW3vHEs2GI0SbxdUvJL1NHbajci7f2dGts3B4eWk4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728998000; c=relaxed/simple; bh=plcaK76hkid5gnT1x7iHYL/VKTUqMiIgtcj1DUiEGD8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=UmsT6mFKMn9Ktq5QPAoNayuhx2hhKc+by1GWVuSXpRWEDwXRiKwp8hQSjmAKZM0Gpld4+sOjGe4Y1mqswBnDY8By4pt1Szez93rRuKJNXw5L0zU8rGxoksZK78wIN4F9A2XQ2Ez0uT8MHIrHw+ZrUFarxdDWMMZHkzNcswoOasw= 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=P4XDAhzW; arc=none smtp.client-ip=170.10.129.124 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="P4XDAhzW" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1728997996; 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=6BlepldiLdUI0lbFpeXtxxXgw7IF9mMia2QYyFoiN3M=; b=P4XDAhzW60uy6YPRK+3NvBy477veP6UQW+l3Q/B6znHHpNlPlx8T4awnq2iHqXC2fJKDNw 0lalPawJFLIQ5+7aPsRenhuS3V9DLX5VdGcP0aTUcoOoCbCUH0VKe+c1mO/AAJDgTAMqIt fH9pCKCDmWrioOqvmgO1ANe8wqhS6aQ= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-91-1KzhV59UMvixEfQD256mAQ-1; Tue, 15 Oct 2024 09:13:15 -0400 X-MC-Unique: 1KzhV59UMvixEfQD256mAQ-1 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-431159f2864so28058945e9.0 for ; Tue, 15 Oct 2024 06:13:15 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1728997994; x=1729602794; 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=6BlepldiLdUI0lbFpeXtxxXgw7IF9mMia2QYyFoiN3M=; b=TfW2tu92gOajyBPb8X71yk+IRzRD973uw9UhVDaSfrm6GdBt8rTv8KiegKEaqSwT2/ ye5Hr+B5XTQDvtNbZSP9qKzJwt/SqsZtodTFvxF6pXfCOLX5xN1euFRZ3iBb1EqsfWYp n6+ng3KYhe3Vtm23O4+23bShsytiDcFUt5jBd+GsGm0gcDdGk+fh/qKtDv96Wbixx+s3 I6FLJoyA6HsfGcRaBBKCsA0o8NvgtWjgiTXAKNCqgTAPvx/2rji3csPhviii9Lz1io+P VAgVa/VuFub6WEsyDiMVLEPgbZ2/rjwOhsgK6lnCa90+q1FCBThGs4FwM8bbHiHJKJXQ hDow== X-Gm-Message-State: AOJu0YwgniBCAwg6/QyaUnGucc8/vgX6enNzYGqr9Quu99dG3BoUR8gY 4LnC0IGbEZY/eOVP3jcrUVyTyBfgdN4WQ1OeGi2sj73Jzn2xSmf5yYz6xoIGWl2nWQ87pRt/s5j XkSYk9THB8+QTUD3dI6xEahoLdAWD6RA86ayW9BzdLRZIhXmI0sphRweYBmKiDjGzJe1dHXxM6U 24d89QzpwHNc8NiwvqZxquVrYzDCze8SRnvnrJyw3GxE4r X-Received: by 2002:a05:600c:5012:b0:426:8884:2c58 with SMTP id 5b1f17b1804b1-4314a284c97mr4145975e9.4.1728997994348; Tue, 15 Oct 2024 06:13:14 -0700 (PDT) X-Google-Smtp-Source: AGHT+IECcu2tYyH+BZRAphlRpRfkiQfa30pn2M2Jspl7YwgWKpkMZCrMZzAXuO/knsNDyrMRBiqr1g== X-Received: by 2002:a05:600c:5012:b0:426:8884:2c58 with SMTP id 5b1f17b1804b1-4314a284c97mr4145685e9.4.1728997993912; Tue, 15 Oct 2024 06:13:13 -0700 (PDT) Received: from ?IPV6:2003:cb:c730:9700:d653:fb19:75e5:ab5c? (p200300cbc7309700d653fb1975e5ab5c.dip0.t-ipconnect.de. [2003:cb:c730:9700:d653:fb19:75e5:ab5c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4313f6b3215sm17480725e9.34.2024.10.15.06.13.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 15 Oct 2024 06:13:13 -0700 (PDT) Message-ID: <4898fdf4-7c88-4697-9df4-64fd8a900e95@redhat.com> Date: Tue, 15 Oct 2024 15:13:11 +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 v1] mm/pagewalk: fix usage of pmd_leaf()/pud_leaf() without present check To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, syzbot+7d917f67c05066cec295@syzkaller.appspotmail.com, Andrew Morton , Jann Horn References: <20241015111236.1290921-1-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: <20241015111236.1290921-1-david@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 15.10.24 13:12, David Hildenbrand wrote: > pmd_leaf()/pud_leaf() only implies a pmd_present()/pud_present() check on > some architectures. We really should check for > pmd_present()/pud_present() first. > > This should explain the report we got on ppc64 (which has > CONFIG_PGTABLE_HAS_HUGE_LEAVES set in the config) that triggered: > VM_WARN_ON_ONCE(pmd_leaf(pmdp_get_lockless(pmdp))); > > Likely we had a PMD migration entry for which pmd_leaf() did not > trigger. We raced with restoring the PMD migration entry, and suddenly > saw a pmd_leaf(). In this case, pte_offset_map_lock() saved us from more > trouble, because it rechecks the PMD value, but we would not have processed > the migration entry -- which is not too bad because the only user of > FW_MIGRATION is KSM for unsharing, and KSM only applies to small folios. > > Further, we shouldn't re-read the PMD/PUD value for our warning, the > primary purpose of the VM_WARN_ON_ONCE() is to find spurious use of > pmd_leaf()/pud_leaf() without CONFIG_PGTABLE_HAS_HUGE_LEAVES. > > As a side note, we are currently not implementing FW_MIGRATION support > for PUD migration entries, which likely should exist due to hugetlb. Add > a TODO so this won't fall through the cracks if more FW_MIGRATION users > get added. > > Fixes: aa39ca6940f1 ("mm/pagewalk: introduce folio_walk_start() + folio_walk_end()") > Reported-by: syzbot+7d917f67c05066cec295@syzkaller.appspotmail.com > Closes: https://lkml.kernel.org/r/670d3248.050a0220.3e960.0064.GAE@google.com > Cc: Andrew Morton > Cc: Jann Horn > Signed-off-by: David Hildenbrand > --- Was able to write a quick reproducer and verify that the issue no longer triggers with this fix. https://gitlab.com/davidhildenbrand/scratchspace/-/blob/main/reproducers/move-pages-pmd-leaf.c Without this fix after a couple of seconds in a VM with 2 NUMA nodes: [ 54.333753] ------------[ cut here ]------------ [ 54.334901] WARNING: CPU: 20 PID: 1704 at mm/pagewalk.c:815 folio_walk_start+0x48f/0x6e0 [ 54.336455] Modules linked in: ... [ 54.345009] CPU: 20 UID: 0 PID: 1704 Comm: move-pages-pmd- Not tainted 6.12.0-rc2+ #81 [ 54.346529] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-2.fc40 04/01/2014 [ 54.348191] RIP: 0010:folio_walk_start+0x48f/0x6e0 [ 54.349134] Code: b5 ad 48 8d 35 00 00 00 00 e8 6d 59 d7 ff e8 08 74 da ff e9 9c fe ff ff 4c 8b 7c 24 08 4c 89 ff e8 26 2b be 00 e9 8a fe ff ff <0f> 0b e9 ec fe ff ff f7 c2 ff 0f 00 00 0f 85 81 fe ff ff 48 8b 02 [ 54.352660] RSP: 0018:ffffb7e4c430bc78 EFLAGS: 00010282 [ 54.353679] RAX: 80000002a3e008e7 RBX: ffff9946039aa580 RCX: ffff994380000000 [ 54.355056] RDX: ffff994606aec000 RSI: 00007f004b000000 RDI: 0000000000000000 [ 54.356440] RBP: 00007f004b000000 R08: 0000000000000591 R09: 0000000000000001 [ 54.357820] R10: 0000000000000200 R11: 0000000000000001 R12: ffffb7e4c430bd10 [ 54.359198] R13: ffff994606aec2c0 R14: 0000000000000002 R15: ffff994604a89b00 [ 54.360564] FS: 00007f004ae006c0(0000) GS:ffff9947f7400000(0000) knlGS:0000000000000000 [ 54.362111] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 54.363242] CR2: 00007f004adffe58 CR3: 0000000281e12005 CR4: 0000000000770ef0 [ 54.364615] PKRU: 55555554 [ 54.365153] Call Trace: [ 54.365646] [ 54.366073] ? __warn.cold+0xb7/0x14d [ 54.366796] ? folio_walk_start+0x48f/0x6e0 [ 54.367628] ? report_bug+0xff/0x140 [ 54.368324] ? handle_bug+0x58/0x90 [ 54.369019] ? exc_invalid_op+0x17/0x70 [ 54.369771] ? asm_exc_invalid_op+0x1a/0x20 [ 54.370606] ? folio_walk_start+0x48f/0x6e0 [ 54.371415] ? folio_walk_start+0x9e/0x6e0 [ 54.372227] do_pages_move+0x1c5/0x680 [ 54.372972] kernel_move_pages+0x1a1/0x2b0 [ 54.373804] __x64_sys_move_pages+0x25/0x30 -- Cheers, David / dhildenb