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b=OecW2CfXJieTrB7VBUxXkqof4xzWAFg2wN21LWTC1OzemsK6eQ6AAdAZmAT6ldB1L a/M2ao/MHuGQSuiEAOBx7T0JW793vr/a7lQ+IjjJ8ms6iXtgJaX2RqWwS6cKoZpME2 sqRoUS+PHlDf1In0q7O9x0LNBlCMNmbULpeFW8hH1b4fj9s+2MRB9hgaxVfq16zkdM FVgBAeioYS3z0aoF+ieDJdsFOUx23RCBfe4jVyCGVtyT2qFmY8TKbOZupgfE++PwA2 b+yWg2uCec3N+AAfmlfF87CS+ZpJp0GogKnccW3tGpG2P2cSAIuJ2Y+NwGWDZ1YYhK 3dwJedZql+jBQ== Message-ID: <892b2a73-4dbd-4090-89c5-46929530b855@kernel.org> Date: Mon, 6 Jul 2026 20:30:29 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: migrate_device: fix pte_pfn/pte_dirty called on non-present PTE To: Kefeng Wang , Andrew Morton Cc: Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , linux-mm@kvack.org References: <20260706111958.3649651-1-wangkefeng.wang@huawei.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260706111958.3649651-1-wangkefeng.wang@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 0D1044000B X-Stat-Signature: ko815s4r1ddqtae9x69j15wxqqmax553 X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1783362635-65330 X-HE-Meta: U2FsdGVkX18UG6FT6KpTktSV+J7RB/2fANXCpTNLKbUoX16RO7OipmU35EliTkw2C1i5OpDk6flnQJ4HNO2pQOyN5sGfbPlpkFkl94u7nsjI+IbLcmq66/reg76pAosGhOKZgxG98/U8srLOhXr98XV8OUp+Nt2Ha0QaJCkoLCTcDPuOEYiZpmBA5gSUqLUYlairLx/V6S8F7TW1l8g1xCR0msTr6Epo/Wp58LMCgWjgrT+7Lx4YQL2MnouYi/+sIuhgA++d/oKKUqiSgJZGAQ6C8aPMj2fAaVfL+806pdzkLplNyAwGssXZ3cTw5ywzdm1yiZAF6th/ifU5wJUnLJtsi8Kbety6yaWzmdZoiud6fTr/GT0i5PBfUF1LPrOvYgH7/isZfLJMH2UhNXTJPa8rv7ba/0I/Pvnn4+xJge59iktvJaoJf82bD2jdCs2Oc+QvVYgwBqmeoh1314Jr30efxlXiujRuUxIR1gj3jpO5ZdXZzbKskP4DwwsdSkCzKsQeePNJn1sl7QCPUcdpfNB/a6e3bwp4dv0PMBbPRxIacUQ4FFgzGi5nb9NjDrTtFtQzl+Jrz8qNJ3idr4kU0hmhhl/yDkEQ4KcdkxaQh4X7iZrbhdI780SsSIzhad6lWw1UzUILklhFOPpegkA4zktKxxs4xcWz65xZCfcuZW/+iDPRd12VVwtwRBvRYuU3UiDWKCRV5qPYC+rRdHuunc1AT1/8q7VSjLQdkQVd87eoGewkQ9J/HEeuNp5XRRwz8k89mCTYTdxNVnixTugmkIEs53wi5bwaOo4pmpfCInUgmAXY1UeUKeTeO7Y5v7h0P+suKWZlJuCO5vX7o4AU985nEIKiue4NfLzVjltsrhkWPAUE+qLgFKt0CkCA9hf0Dz+owmY3X+sF/WJrCnAG/sn4bEUYuTqIE4qgRmDXenTO1tt+oVlT49m5MzzepmXZDqqo7hbdpRZr5BZtS6U NW77iCfP uRkQWePUdz438FY2VqDWYYJO/g/Tc0jF0AOYn3fjHDKC9e2nwz68PKXNF0f0jklC7vF0NeqsDJEF3rnZxCDYEax2Bqoe4K5c31Cro1Va8KsE6jWYYXTqRDEFZnDkQqOktxw7wOhUSkreVx5t4MBgeazZtNxG43yaui7AprttJo8sU7QzygxKiYPooOJ6QegB9TRpfz2UYf8qXw8QcBr5Q8deJeJ5mEqFaRSyBrmE2Py8KKoMVCAewSXhpR3cTkeSW8kuYoZ5vn+dtEko1s/zXkXlrgldRSZRhsgJzBDd9HNmXlOlmlfOatd776vpGX4Bq/tuDvnQqd+G6hVKIFKyXxpZLywrwRiWBfEQMFHfavc0Io2ZfTxaVDHjV37nqpbBzLh5mE0HMaXT/wUGt0O5iCf42hQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/6/26 13:19, Kefeng Wang wrote: > pte_pfn() and pte_dirty() have undefined behaviour when called on a > non-present PTE. In migrate_vma_collect_pmd(), these functions may be > invoked on non-present entries (e.g., swap PTEs), leading to potential Certainly not real swap PTEs, as the previous function handling is if (!pte_present(pte)) { ... if (!softleaf_is_device_private(entry)) goto next; Only device-private entries? > crashes from pte_pfn() or incorrect dirty folio accounting from > pte_dirty(). Fix both by guarding with pte_present() checks. > > Fixes: fd35ca3d12cc ("mm/migrate_device.c: copy pte dirty bit to page") > Fixes: a3589e1d5fe3 ("mm/migrate_device.c: add missing flush_cache_page()") I suspected device-private code, but indeed, these seem to be added afterwards. But a3589e1d5fe3 only moved the flush_cache_page()? So that one seems wrong. > Signed-off-by: Kefeng Wang > --- > mm/migrate_device.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/mm/migrate_device.c b/mm/migrate_device.c > index 052167f9ad54..6e711381f092 100644 > --- a/mm/migrate_device.c > +++ b/mm/migrate_device.c > @@ -411,7 +411,8 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > bool anon_exclusive; > pte_t swp_pte; > > - flush_cache_page(vma, addr, pte_pfn(pte)); > + if (pte_present(pte)) > + flush_cache_page(vma, addr, pte_pfn(pte)); > anon_exclusive = folio_test_anon(folio) && > PageAnonExclusive(page); > if (anon_exclusive) { > @@ -432,7 +433,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > migrate->cpages++; > > /* Set the dirty flag on the folio now the pte is gone. */ > - if (pte_dirty(pte)) > + if (pte_present(pte) && pte_dirty(pte)) > folio_mark_dirty(folio); > > /* Setup special migration page table entry */ Changes look good. -- Cheers, David