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[79.242.53.59]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-438b318c176sm16487075e9.3.2025.01.22.00.52.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 22 Jan 2025 00:52:13 -0800 (PST) Message-ID: Date: Wed, 22 Jan 2025 09:52:11 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: page_isolation: avoid call folio_hstate() without hugetlb_lock To: Liu Shixin , Andrew Morton , Kefeng Wang , Muchun Song , Zi Yan , Johannes Weiner , "Kirill A . Shutemov" , Nanyong Sun Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250122061151.578768-1-liushixin2@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/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: <20250122061151.578768-1-liushixin2@huawei.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: T-Id2bdQgwPSbhNrIOWzTyJtJuDgujcRrOUplMSat2E_1737535934 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: 6p4e9s46xuqt3g6z7rczwqq1uoq587x9 X-Rspamd-Queue-Id: 20A09100007 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1737535937-361305 X-HE-Meta: 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 fNKAmqDH 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 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 22.01.25 07:11, Liu Shixin wrote: > I found a NULL pointer dereference as followed: > > BUG: kernel NULL pointer dereference, address: 0000000000000028 > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 0 P4D 0 > Oops: Oops: 0000 [#1] SMP PTI > CPU: 5 UID: 0 PID: 5964 Comm: sh Kdump: loaded Not tainted 6.13.0-dirty #20 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1. > RIP: 0010:has_unmovable_pages+0x184/0x360 > ... > Call Trace: > > set_migratetype_isolate+0xd1/0x180 > start_isolate_page_range+0xd2/0x170 > alloc_contig_range_noprof+0x101/0x660 > alloc_contig_pages_noprof+0x238/0x290 > alloc_gigantic_folio.isra.0+0xb6/0x1f0 > only_alloc_fresh_hugetlb_folio.isra.0+0xf/0x60 > alloc_pool_huge_folio+0x80/0xf0 > set_max_huge_pages+0x211/0x490 > __nr_hugepages_store_common+0x5f/0xe0 > nr_hugepages_store+0x77/0x80 > kernfs_fop_write_iter+0x118/0x200 > vfs_write+0x23c/0x3f0 > ksys_write+0x62/0xe0 > do_syscall_64+0x5b/0x170 > entry_SYSCALL_64_after_hwframe+0x76/0x7e > > As has_unmovable_pages() call folio_hstate() without hugetlb_lock, there > is a race to free the HugeTLB page between PageHuge() and folio_hstate(). > There is no need to add hugetlb_lock here as the HugeTLB page can be freed > in lot of places. So it's enough to unfold folio_hstate() and add a check > to avoid NULL pointer dereference for hugepage_migration_supported(). > > Fixes: 464c7ffbcb16 ("mm/hugetlb: filter out hugetlb pages if HUGEPAGE migration is not supported.") > Signed-off-by: Liu Shixin > --- > mm/page_isolation.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index 7e04047977cf..2a38f429defb 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -83,7 +83,14 @@ static struct page *has_unmovable_pages(unsigned long start_pfn, unsigned long e > unsigned int skip_pages; > > if (PageHuge(page)) { > - if (!hugepage_migration_supported(folio_hstate(folio))) > + struct hstate *h; > + > + /* > + * The huge page may be freed so can not > + * use folio_hstate() directly. > + */ > + h = size_to_hstate(folio_size(folio)); > + if (h && !hugepage_migration_supported(h)) > return page; So in case we trigger the race as described, we assume the page is movable (just freed to the buddy). Makes sense to me. Acked-by: David Hildenbrand -- Cheers, David / dhildenb