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Howlett" , Mike Rapoport References: <20260623-page_ext-v3-1-a89799a5367c@oss.qualcomm.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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: zkc5ox69uckpseaeeu834thcsgm8rppo X-Rspamd-Queue-Id: C4BF140014 X-Rspamd-Server: rspam06 X-HE-Tag: 1782200289-799975 X-HE-Meta: U2FsdGVkX1+Akfo65vRIpCR4uB2tMchAM8qj0xbDGRCNXP4l+T/MDU8S+vm4sz//+fuJAytwSSro7LXoCA+4w9qJmL82HwDmG9usn9fhoOKiSPCQ2BrsFAlA/NrHm2AKQCn3nXsCRZeCOAmoLtkHhx05ipTGTEDM7IIQwkwJrMnlLc6kzReedBcU6L06M1GqE6ewC2YNNNCxJA/nAdyLvXkQyI9DghhWaOzAdUeiCZhxVi/XORqEQU/in2BvZVSQmpy/KxGbsB6VdAlmUHbcg+grkudw+7tE63rJPkCOwm3IrhsN6Ug9UsPabkMDMPihJBlKRX9js1ExJNmxe01qZhAy/6tXtug90kuM1yrw6TBaCIDcRFzGHiR7D81OQLBnjYlpTkzauM2Ncz3+PBQvT2WcSTHl/YNHUfOk2w12/eo3pTCEO5XUTpUvmZq4d/61y3elysILSx5g5wXZo0Ho8yY9XRrpGM9CzpoxXDvY1Ua+nl3t0YbgxPSebhgEAJdi8YqcB1MF6k3Jiwbm0dPxEVMZRoLdpBExbMsu6nLebJktqkssRIX2G5rEyZecStSlPz3gWund4MRqbAV0dwFDNzYsBgmAhhGlVpA9pSnDVosMqXPhwo58P5dEmBOn7eTI/Jj4bxD5HJKRWvbRwjUQyrXCBVuW+Yud05AaSKWzZNfFnmH8r0D2MNjHH2fnccRz0TzTRJfIF15pkVYulVCBDZSxe0uRAAGRR+0K5umykfKsaQGEIMDe3X/O33rEVEZmH5Tf8hBYLjDVumumYTOYKkZy/yXgAU243+iu2lrHj4C/J6tT3qXqr2zrH5o35MRbysxMfa3/cLCyxPzNJ3rA1JcsxEbsqTuWjyoHBx0qOjzw1aONjp8hJtW/AMSL1kF8ccDp4Xu21mQPn3LetHDKZU570ycORFk7BJaTj3wF/96dCwCBrIXKQh0CFLF/yjaDXmN2BiHvmgqi3dBD1J0 eWT2W6WI 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/23/26 01:27, Zi Yan wrote: > On Mon Jun 22, 2026 at 5:18 PM EDT, Ketan wrote: >> The page_ext iteration API does not validate if the PFN still >> belongs to a valid section while advancing the iterator. When >> dynamically adding memory in the hotplug path, it can lead to a >> NULL pointer dereference during page_ext_lookup at the boundary >> of the last valid section when iterator count equals __pgcount. >> >> The for_each_page_ext() macro calls page_ext_iter_next() as its >> loop increment. for_each_page_ext() does a >> "__page_ext = page_ext_iter_next(&__iter)" at the end. This >> causes page_ext_iter_next() to increment iter->index past >> __pgcount and call page_ext_lookup(start_pfn + __pgcount). >> During memory hotplug (online), the PFN at start_pfn + __pgcount >> may belong to a section that has not yet been initialized, >> causing page_ext_lookup() to trigger a NULL pointer dereference. >> >> [ 14.555124][ T846] Call trace: >> [ 14.555125][ T846] lookup_page_ext+0x6c/0x108 (P) >> [ 14.555127][ T846] page_ext_lookup+0x30/0x3c >> [ 14.555129][ T846] __reset_page_owner+0x11c/0x260 >> [ 14.571201][ T846] __free_pages_ok+0x5e8/0x8e0 >> [ 14.571204][ T846] __free_pages_core+0x78/0xf0 >> [ 14.571206][ T846] generic_online_page+0x14/0x24 >> [ 14.597782][ T846] online_pages+0x178/0x30c >> [ 14.597784][ T846] memory_block_change_state+0x284/0x32c >> [ 14.597787][ T846] memory_subsys_online+0x4c/0x64 >> [ 14.597789][ T846] device_online+0x88/0xb0 >> [ 14.597791][ T846] online_memory_block+0x30/0x40 >> [ 14.597793][ T846] walk_memory_blocks+0xac/0xe8 >> [ 14.597794][ T846] add_memory_resource+0x280/0x298 >> [ 14.656161][ T846] add_memory+0x60/0x98 >> >> Move the iteration boundary enforcement inside the iterator >> functions, so callers cannot inadvertently access beyond the >> requested range. >> >> Fixes: 9039b9096ea2 ("mm: page_owner: use new iteration API") >> Cc: stable@vger.kernel.org >> Suggested-by: David Hildenbrand >> Suggested-by: Matthew Wilcox >> Signed-off-by: Ketan Kishore >> Tested-by: syzbot@syzkaller.appspotmail.com > This is probably not needed. Agreed, we usually don't include this. Acked-by: David Hildenbrand (Arm) -- Cheers, David