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[2003:cb:c72f:c700:a76f:473d:d5cf:25a8]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-37d1691a4cdsm7442141f8f.27.2024.10.08.01.26.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Oct 2024 01:26:43 -0700 (PDT) Message-ID: <9e4e3094-00a2-43bc-996f-af15c3168e3a@redhat.com> Date: Tue, 8 Oct 2024 10:26:42 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] mm: avoid clearing user movable page twice with init_on_alloc=1 To: Zi Yan , linux-mm@kvack.org, Alexander Potapenko , Kees Cook Cc: Andrew Morton , "Matthew Wilcox (Oracle)" , Miaohe Lin , Kefeng Wang , John Hubbard , "Huang, Ying" , linux-kernel@vger.kernel.org References: <20241007182315.401167-1-ziy@nvidia.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/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: <20241007182315.401167-1-ziy@nvidia.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 0F07C1C0014 X-Stat-Signature: 5b8fecmc1yr5n1hwxxdcqxfsdte8okwk X-Rspam-User: X-HE-Tag: 1728376006-765111 X-HE-Meta: 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 2rkRtM/o zVlPlxs2k1+GUTnhpD9A9ds/+Q+hohDEsF1cVxBjzPKHk8O7ymJWM/I0AUzukr1xjI1vpXMWyJ2kTbzeoDHjviKDm3OHMUgLNAAp+tPL3LP4GlI99DCs54kqitzvHO3nyKjLwWBMSMosLMw+ISXy0fhCRua7AssWR+fgqcK3fb7mbmpAuSB4Z2R/NO92ACVkU87lEAD+mTZ7JgdGGiy6BfaspSXZU/GpHxi/Swu0RzCsLISR3+L2oLwduihM3OXNs7I8ue9Cln4QP8FG6P8wKPghb5RDQ1NKXsPqVzBuyfY5zv/VylYNpMAY54vhJ6JXkhRxg0AvSggmi/CWnhI4hdEz4bUdCzHrYsIvmq7+kaUSLI7l8YvmxeRk98hr03l4i2XkMZP9Jv897QKyQsTeSUvGcXrEk37HqQuapqe4qTT86GprLg84DEqMDGpdMDe43XXBudvxmQbNOZzwuso2UxTmhmA== 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 07.10.24 20:23, Zi Yan wrote: > Commit 6471384af2a6 ("mm: security: introduce init_on_alloc=1 and > init_on_free=1 boot options") forces allocated page to be cleared in > post_alloc_hook() when init_on_alloc=1. > > For non PMD folios, if arch does not define > vma_alloc_zeroed_movable_folio(), the default implementation again clears > the page return from the buddy allocator. So the page is cleared twice. > Fix it by passing __GFP_ZERO instead to avoid double page clearing. > At the moment, s390,arm64,x86,alpha,m68k are not impacted since they > define their own vma_alloc_zeroed_movable_folio(). > > For PMD folios, folio_zero_user() is called to clear the folio again. > Fix it by calling folio_zero_user() only if init_on_alloc is set. > All arch are impacted. > > Signed-off-by: Zi Yan > --- > include/linux/highmem.h | 14 ++------------ > mm/huge_memory.c | 4 +++- > 2 files changed, 5 insertions(+), 13 deletions(-) > > diff --git a/include/linux/highmem.h b/include/linux/highmem.h > index 930a591b9b61..4b15224842e1 100644 > --- a/include/linux/highmem.h > +++ b/include/linux/highmem.h > @@ -220,18 +220,8 @@ static inline void clear_user_highpage(struct page *page, unsigned long vaddr) > * Return: A folio containing one allocated and zeroed page or NULL if > * we are out of memory. > */ > -static inline > -struct folio *vma_alloc_zeroed_movable_folio(struct vm_area_struct *vma, > - unsigned long vaddr) > -{ > - struct folio *folio; > - > - folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vaddr, false); > - if (folio) > - clear_user_highpage(&folio->page, vaddr); > - > - return folio; > -} > +#define vma_alloc_zeroed_movable_folio(vma, vaddr) \ > + vma_alloc_folio(GFP_HIGHUSER_MOVABLE | __GFP_ZERO, 0, vma, vaddr, false) > #endif > > static inline void clear_highpage(struct page *page) > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index a7b05f4c2a5e..ff746151896f 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1177,7 +1177,9 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf, > goto release; > } > > - folio_zero_user(folio, vmf->address); > + if (!static_branch_maybe(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, > + &init_on_alloc)) > + folio_zero_user(folio, vmf->address); > /* > * The memory barrier inside __folio_mark_uptodate makes sure that > * folio_zero_user writes become visible before the set_pmd_at() I remember we discussed that in the past and that we do *not* want to sprinkle these CONFIG_INIT_ON_ALLOC_DEFAULT_ON checks all over the kernel. Ideally, we'd use GFP_ZERO and have the buddy just do that for us? There is the slight chance that we zero-out when we're not going to use the allocated folio, but ... that can happen either way even with the current code? -- Cheers, David / dhildenb