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[2003:d8:2f0c:c200:fa4a:c4ff:1b32:21ce]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-471144b5c29sm241641755e9.12.2025.10.20.10.14.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Oct 2025 10:14:40 -0700 (PDT) Message-ID: <81fc5322-6ab4-4830-9b2e-15d834b461c2@redhat.com> Date: Mon, 20 Oct 2025 19:14:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-new v3 1/1] mm/khugepaged: guard is_zero_pfn() calls with pte_present() To: Lance Yang , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com Cc: ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, ioworker0@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Wei Yang References: <20251020151111.53561-1-lance.yang@linux.dev> 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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+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: <20251020151111.53561-1-lance.yang@linux.dev> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: HGn0gNF44BvqQf-2wYORyR37bw7f8gGjpaBzOLbfxQI_1760980481 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 61CCD140011 X-Stat-Signature: m9tsdbd86bjr3pyeknesdgefd4yc599h X-HE-Tag: 1760980484-748750 X-HE-Meta: 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 JgpXPBf1 7jQT8a0krdw0hA1TzGsK9TmQVvKpwaFVU0I5mbw2oFQq+tpySdA0Vg8yKuxJD5sW0eLZT3gHkZMuixBTTDGZv37vQcXQJ0OftVTlta4YS5NUyLM9edYmJu0tOeeC+j2KnFOsd31OZLh5eDDSJniiiEYGYTYVEU+5IGfUDrdJGdeDDKrslK1YUHqMLOFZD6B+U8eVUyTjsIx82/ivja2d29MqpodIOIEv7e5oEdfDpAQjsm0CcdPfz6qrUGCKIxI70seH2R2jY9ZX/xkkCLLr23xGjDQA/PD2/PHcEvVHNmBQKQ/nvKXdpVPbli0OhTkWpnlqHwRfiBPICvZLwSA5TdGONp2l3zdlxB28CMvHE48FxPw+gPyH5b4ZuCtdfp7KGOJ+3/IIdaoRvDZlxwrAlPvbCi+5evw0mp5o0tpxIiWthQXyFtj1xJ236i7QrSHpuA3JW6nRWltHHKll6BvgzUW+H12LuWzCpP0xXR9i1pxKF3nr65wkqLjv/ELtfLIAJ4YZr2vswG9LC18AqFfbLbrH7P+cH0a6pbHx0diVPeFdbHKSePl91/YRLakfzQJyp+fyahk6F6rZxtG805puvh7Gp3QIC4tOSwKRZBtb+e9nJ+qAZ1Nt5rHL4gYPYbzk50HD6z84Yx+UF4jU36J1Rd8NGkQT4ijiZUfTp 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 20.10.25 17:11, Lance Yang wrote: > From: Lance Yang > > A non-present entry, like a swap PTE, contains completely different data > (swap type and offset). pte_pfn() doesn't know this, so if we feed it a > non-present entry, it will spit out a junk PFN. > > What if that junk PFN happens to match the zeropage's PFN by sheer > chance? While really unlikely, this would be really bad if it did. > > So, let's fix this potential bug by ensuring all calls to is_zero_pfn() > in khugepaged.c are properly guarded by a pte_present() check. > > Suggested-by: Lorenzo Stoakes > Reviewed-by: Nico Pache > Reviewed-by: Dev Jain > Reviewed-by: Baolin Wang > Reviewed-by: Wei Yang > Signed-off-by: Lance Yang > --- Works for me! Acked-by: David Hildenbrand -- Cheers David / dhildenb