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 0208C1DEFDE for ; Tue, 8 Oct 2024 08:21:15 +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=1728375677; cv=none; b=mbol7dZctZh1KY8JbFFqCJMIv9+TkbasGKi4qr3RacjK4Vql8Dd9o4TXii36pn4oq0U6/ZNXzzQ4h6RdZQiaCSUvl40x5KB2MJyuVC6dI51bPkzH6PPvYPfmHQ72qD90dg1G4oOrptlUjfRCJsAjMRMqBfLAdioTi881m6GtsSw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728375677; c=relaxed/simple; bh=jIc5H1FXGoZrRnjNg1/Mn7Rw0fxijTdz12BOUiiwW2w=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=AetH/92yWiXkCwXcE6AMllbJHG1RAswjbq+7juBRiImsPT/tiRr8QkwhM/kMqEKJPOrZa2KPexfQx+VVrUy4IwcqE2hTB516tWifYWr+06dBSXuWtydQ8PUzUHLDpThR1njPFvAKJwnWpgCFkvD4Lm6TDS6Bsn9MMzCqlBpNdWY= 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=AbpGOyr8; 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="AbpGOyr8" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1728375674; 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=rqosfSkDCFYhrwQm7M66U0/q2w7YrSsk+o2s9MBJQz8=; b=AbpGOyr8QcQ7uXtu/b7S6Jojc1GuL1Es4E4KnCUxf928mv7AVM9J4A8M/NF7oBA0Yp6gLX qa2YohMRvd5cq6DgRGd1zJ5PYcOB6IOHtRbRkiF28VSuN4/Nzu5HN0ju1aR5ll6+szbJmb VJJS+1pou2B0KTxc/y/744VVKyNnLCI= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-115-uE3-7p71MzCnYFK96Bl0wA-1; Tue, 08 Oct 2024 04:21:13 -0400 X-MC-Unique: uE3-7p71MzCnYFK96Bl0wA-1 Received: by mail-wr1-f72.google.com with SMTP id ffacd0b85a97d-37ccc188d6aso3600188f8f.2 for ; Tue, 08 Oct 2024 01:21:13 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1728375672; x=1728980472; h=content-transfer-encoding:in-reply-to:organization:autocrypt:from :content-language: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=rqosfSkDCFYhrwQm7M66U0/q2w7YrSsk+o2s9MBJQz8=; b=ntd7AOvZQVZaHAP8D+NnG4ec+UNkPtSu4llCDJRpjAkClKcZaDsD+IZxMd2CZxhVR7 EFt17bJYNoiJqJFjGlRVRhqL7Htz2vtTlk8eQQEMJG9lETGz1OxpYNq/f/m2r4bR3oyC hhKriyXcuoMHpglVuPGpgGRlZNxc92IJNk8LjfDqt0oBEYeSpSLYy8ABVRxOMBIos8Dx bb+8IfFCsdlmQA1f8FwOrLAAcGamKvLUmlZ6IKIo3Pb0REFLyZ0qYVsn/rCIlPZN74+n HRVnUHPjCOR7QCHnCeYHfCWwGQN2kWdh1bdHzKLuc5GTKXsQ+5zoXL8EKoDP6C60O8MZ KJ7w== X-Forwarded-Encrypted: i=1; AJvYcCX7f2P88cKegnBYe2j0sRKYi5cXAvlPcrsKHhczOh3ceKtpZOi5K1wJe4PxWuuXGDfqN9f6TDc=@vger.kernel.org X-Gm-Message-State: AOJu0YxpLsvaPLxyZqUvi0vJn3bSXqOn9QHvuoUpUQiqNEP49+AqxazD jygmoGiGsEE9CWaAHWfXdAB4Iz4IQyo4RNB3sgtkXkj08szyjPUCrSk/n3i6CnRRoEm4lNvgOgs Fc7Ujm01Hi7kHznVheAIbw2/xSZUydhNLIpedZF8Y+kwFZjaRYkkrdA== X-Received: by 2002:a5d:5f54:0:b0:37c:cfdc:19ba with SMTP id ffacd0b85a97d-37d0e751784mr15394771f8f.28.1728375672223; Tue, 08 Oct 2024 01:21:12 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEegr1mPVmXtdGKRjNw0OWHkQoTIJu+ZQZHPVx3xgKvhAKp91NIZdq/o3yJ1fDZy5psZjQFpQ== X-Received: by 2002:a5d:5f54:0:b0:37c:cfdc:19ba with SMTP id ffacd0b85a97d-37d0e751784mr15394755f8f.28.1728375671772; Tue, 08 Oct 2024 01:21:11 -0700 (PDT) Received: from ?IPV6:2003:cb:c72f:c700:a76f:473d:d5cf:25a8? (p200300cbc72fc700a76f473dd5cf25a8.dip0.t-ipconnect.de. [2003:cb:c72f:c700:a76f:473d:d5cf:25a8]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-37d1691a47esm7476182f8f.28.2024.10.08.01.21.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Oct 2024 01:21:11 -0700 (PDT) Message-ID: <7201c25f-0b6e-4a8b-b6a1-b09c6730fb32@redhat.com> Date: Tue, 8 Oct 2024 10:21:10 +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] mm/mremap: Fix move_normal_pmd/retract_page_tables race To: Qi Zheng Cc: Jann Horn , akpm@linux-foundation.org, linux-mm@kvack.org, willy@infradead.org, hughd@google.com, lorenzo.stoakes@oracle.com, joel@joelfernandes.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20241007-move_normal_pmd-vs-collapse-fix-2-v1-1-5ead9631f2ea@google.com> <1c114925-9206-42b1-b24b-bb123853a359@bytedance.com> <75fac79a-0ff2-4ba0-bdd7-954efe2d9f41@redhat.com> Content-Language: en-US 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/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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 08.10.24 09:58, Qi Zheng wrote: > > > On 2024/10/8 15:52, David Hildenbrand wrote: >> On 08.10.24 05:53, Qi Zheng wrote: >>> Hi Jann, >>> >>> On 2024/10/8 05:42, Jann Horn wrote: >>> >>> [...] >>> >>>> >>>> diff --git a/mm/mremap.c b/mm/mremap.c >>>> index 24712f8dbb6b..dda09e957a5d 100644 >>>> --- a/mm/mremap.c >>>> +++ b/mm/mremap.c >>>> @@ -238,6 +238,7 @@ static bool move_normal_pmd(struct vm_area_struct >>>> *vma, unsigned long old_addr, >>>>    { >>>>        spinlock_t *old_ptl, *new_ptl; >>>>        struct mm_struct *mm = vma->vm_mm; >>>> +    bool res = false; >>>>        pmd_t pmd; >>>>        if (!arch_supports_page_table_move()) >>>> @@ -277,19 +278,25 @@ static bool move_normal_pmd(struct >>>> vm_area_struct *vma, unsigned long old_addr, >>>>        if (new_ptl != old_ptl) >>>>            spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); >>>> -    /* Clear the pmd */ >>>>        pmd = *old_pmd; >>>> + >>>> +    /* Racing with collapse? */ >>>> +    if (unlikely(!pmd_present(pmd) || pmd_leaf(pmd))) >>> >>> Since we already hold the exclusive mmap lock, after a racing >>> with collapse occurs, the pmd entry cannot be refilled with >>> new content by page fault. So maybe we only need to recheck >>> pmd_none(pmd) here? >> >> My thinking was that it is cheap and more future proof to check that we >> really still have a page table here. For example, what if collapse code >> is ever changed to replace the page table by the collapsed PMD? > > Ah, make sense. > > Acked-by: Qi Zheng Thanks a lot for your review! -- Cheers, David / dhildenb