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[2003:d8:2f19:6500:e1c1:8216:4c25:efe4]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a4d1ed8740sm5369659f8f.83.2025.05.26.05.59.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 26 May 2025 05:59:55 -0700 (PDT) Message-ID: <87521d93-cc03-480d-a2ef-3ef8c84481c9@redhat.com> Date: Mon, 26 May 2025 14:59:54 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/hugetlb: fix kernel NULL pointer dereference when replacing free hugetlb folios To: Ge Yang , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, 21cnbao@gmail.com, baolin.wang@linux.alibaba.com, muchun.song@linux.dev, osalvador@suse.de, liuzixing@hygon.cn References: <1747884137-26685-1-git-send-email-yangge1116@126.com> <07b7d4fd-c600-4de1-aea4-037e148da79b@126.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: <07b7d4fd-c600-4de1-aea4-037e148da79b@126.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: jVM-8UyHmmqpZFkK1oVpkfgKglb1YSzv0H7mAtNY6Ys_1748264396 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 38C0B10000C X-Stat-Signature: rjk4usiuxeiuhmezz1krg8o5i5x8y77b X-Rspam-User: X-HE-Tag: 1748264399-396226 X-HE-Meta: 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 SlhbM0RU 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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 26.05.25 14:57, Ge Yang wrote: > > > 在 2025/5/26 20:41, David Hildenbrand 写道: >> On 22.05.25 05:22, yangge1116@126.com wrote: >>> From: Ge Yang >>> >>> A kernel crash was observed when replacing free hugetlb folios: >>> >>> BUG: kernel NULL pointer dereference, address: 0000000000000028 >>> PGD 0 P4D 0 >>> Oops: Oops: 0000 [#1] SMP NOPTI >>> CPU: 28 UID: 0 PID: 29639 Comm: test_cma.sh Tainted 6.15.0-rc6-zp #41 >>> PREEMPT(voluntary) >>> RIP: 0010:alloc_and_dissolve_hugetlb_folio+0x1d/0x1f0 >>> RSP: 0018:ffffc9000b30fa90 EFLAGS: 00010286 >>> RAX: 0000000000000000 RBX: 0000000000342cca RCX: ffffea0043000000 >>> RDX: ffffc9000b30fb08 RSI: ffffea0043000000 RDI: 0000000000000000 >>> RBP: ffffc9000b30fb20 R08: 0000000000001000 R09: 0000000000000000 >>> R10: ffff88886f92eb00 R11: 0000000000000000 R12: ffffea0043000000 >>> R13: 0000000000000000 R14: 00000000010c0200 R15: 0000000000000004 >>> FS:  00007fcda5f14740(0000) GS:ffff8888ec1d8000(0000) >>> knlGS:0000000000000000 >>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>> CR2: 0000000000000028 CR3: 0000000391402000 CR4: 0000000000350ef0 >>> Call Trace: >>> >>>   replace_free_hugepage_folios+0xb6/0x100 >>>   alloc_contig_range_noprof+0x18a/0x590 >>>   ? srso_return_thunk+0x5/0x5f >>>   ? down_read+0x12/0xa0 >>>   ? srso_return_thunk+0x5/0x5f >>>   cma_range_alloc.constprop.0+0x131/0x290 >>>   __cma_alloc+0xcf/0x2c0 >>>   cma_alloc_write+0x43/0xb0 >>>   simple_attr_write_xsigned.constprop.0.isra.0+0xb2/0x110 >>>   debugfs_attr_write+0x46/0x70 >>>   full_proxy_write+0x62/0xa0 >>>   vfs_write+0xf8/0x420 >>>   ? srso_return_thunk+0x5/0x5f >>>   ? filp_flush+0x86/0xa0 >>>   ? srso_return_thunk+0x5/0x5f >>>   ? filp_close+0x1f/0x30 >>>   ? srso_return_thunk+0x5/0x5f >>>   ? do_dup2+0xaf/0x160 >>>   ? srso_return_thunk+0x5/0x5f >>>   ksys_write+0x65/0xe0 >>>   do_syscall_64+0x64/0x170 >>>   entry_SYSCALL_64_after_hwframe+0x76/0x7e >>> >>> There is a potential race between __update_and_free_hugetlb_folio() >>> and replace_free_hugepage_folios(): >>> >>> CPU1                              CPU2 >>> __update_and_free_hugetlb_folio   replace_free_hugepage_folios >>>                                      folio_test_hugetlb(folio) >>>                                      -- It's still hugetlb folio. >>> >>>    __folio_clear_hugetlb(folio) >>>    hugetlb_free_folio(folio) >>>                                      h = folio_hstate(folio) >>>                                      -- Here, h is NULL pointer >>> >>> When the above race condition occurs, folio_hstate(folio) returns >>> NULL, and subsequent access to this NULL pointer will cause the >>> system to crash. To resolve this issue, execute folio_hstate(folio) >>> under the protection of the hugetlb_lock lock, ensuring that >>> folio_hstate(folio) does not return NULL. >>> >>> Fixes: 04f13d241b8b ("mm: replace free hugepage folios after migration") >>> Signed-off-by: Ge Yang >>> Cc: >>> --- >>>   mm/hugetlb.c | 8 ++++++++ >>>   1 file changed, 8 insertions(+) >>> >>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >>> index 3d3ca6b..6c2e007 100644 >>> --- a/mm/hugetlb.c >>> +++ b/mm/hugetlb.c >>> @@ -2924,12 +2924,20 @@ int replace_free_hugepage_folios(unsigned long >>> start_pfn, unsigned long end_pfn) >>>       while (start_pfn < end_pfn) { >>>           folio = pfn_folio(start_pfn); >>> + >>> +        /* >>> +         * The folio might have been dissolved from under our feet, >>> so make sure >>> +         * to carefully check the state under the lock. >>> +         */ >>> +        spin_lock_irq(&hugetlb_lock); >>>           if (folio_test_hugetlb(folio)) { >>>               h = folio_hstate(folio); >>>           } else { >>> +            spin_unlock_irq(&hugetlb_lock); >>>               start_pfn++; >>>               continue; >>>           } >>> +        spin_unlock_irq(&hugetlb_lock); >> >> As mentioned elsewhere, this will grab the hugetlb_lock for each and >> every pfn in the range if there are no hugetlb folios (common case). >> >> That should certainly *not* be done. >> >> In case we see !folio_test_hugetlb(), we should just move on. >> > > The main reason for acquiring the hugetlb_lock here is to obtain a valid > hstate, as the alloc_and_dissolve_hugetlb_folio() function requires > hstate as a parameter. This approach is indeed not performance-friendly. > However, in the patch available at > https://lore.kernel.org/lkml/1747987559-23082-1-git-send-email-yangge1116@126.com/, > all these operations will be removed. No, you still take locks on anything that is !folio_ref_count(folio). We should really have an early folio_test_hugetlb(folio) check. hugetlb is on most systems out there the absolute *corner case*. -- Cheers, David / dhildenb