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t=1788792608; bh=0mIRzAim8Xm04hf6n5NB+NxEk+eE5bXm5v665dJOtpg=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=oBBZei8fiHVJieUd7Lx21QpFtUu+KnLLeLIBYbntsp5gB1HSyOzJ2aCxPwQTrnzsR ZAV5ezYF7K8Svj2yPyUBGosD9SRvb0Pk+1Bi9o1dFVWx2Tv/7jSjX6oi0HUYKze38r ZkDapIB5ST8+zWkvJyYsQ1rbKV3Oh2LQJvhhfw4H+6HsGG5zQC0+FPDYOJBXL2FSk1 dj6BTOsA7RqNsT0El6XVcv6nydL4/FdBaq9zC3Oc0FOe5VSIZEu2+qjJDRuhMI+fyC QMEJVhJUA/B5pP68gI7p3UQ4lFuzH1BYO9AcCR58lwusE8FgQzCK4yHGJmzAQfoGal M+e2/iEYEUDDw== Message-ID: Date: Mon, 7 Sep 2026 16:50:04 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] mm/gup_test: safely calculate GUP batch size To: Sarthak Sharma , Andrew Morton Cc: Jason Gunthorpe , John Hubbard , Peter Xu , Kiryl Shutsemau , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260903115033.162218-1-sarthak.sharma@arm.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: <20260903115033.162218-1-sarthak.sharma@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: sa66w17ozmekd8k5968z15u6zong5sdi X-Rspamd-Queue-Id: 266C1140005 X-Rspamd-Server: rspam06 X-HE-Tag: 1788792610-162240 X-HE-Meta: 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 bb4YDo34 PDupmT5eWd5r/VgXB2T3ZRoHlzlpOASQ9CmlAOp56w27v5Kw2+V74C+LNxDOwGiWj/+v+tBJKaW2Bys8JuH5WX239NHzi1D6u26R9g9cmu1MgBudFAJ2VJfdfW7EZi8ZhUFcA4mXzftZtB+52LlcReuuI7cyXXiL1nBpa50s/5+PgQ0E4xx115HMtHuBpeUHQKmYpLZ9qNKFh0sb39sVjX175d7/TyhLEy6B5enAXhN++bCVKXOmD1LPiwj2unJ/2MLxPlW/gLiLygp+bAV2ZuR8dzDOtbYKK9L2mGgAQlUfjs0zWV2sSmjcMHPTUoJ2pWUQqnemILisDMxMaHstroerArMbv8OUY9zS1mB2jy7qHUMdh2PqQZokNgapohwb158GqGFY566nwzWQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/3/26 13:50, Sarthak Sharma wrote: > __gup_test_ioctl() calculates the end of a GUP batch using: > > next = addr + nr * PAGE_SIZE; > > If nr is too large, it can cause next to overflow and wrap around. > If it wraps, the next > end check is bypassed and a large value > of nr is passed to the GUP call, even though the pages array was > allocated according to gup->size. This can lead to out of bounds writes. > > Also, when fewer than PAGE_SIZE bytes remain, the calculated batch > contains zero pages. The code still calls GUP functions with pages + i, > which can point past the allocated array. > > Calculate nr by taking the minimum of the number of pages per call and > the pages remaining in the address range. Stop processing when no > pages remain and calculate the end of the batch using this bounded > value of nr. > > Fixes: 64c349f4ae78 ("mm: add infrastructure for get_user_pages_fast() benchmarking") > Signed-off-by: Sarthak Sharma > --- > Sashiko reported the issue fixed by this patch while reviewing the patch > "mm/gup_test: report actual pinned bytes". That patch has been applied to > mm-new. Since the two fixes are independent, this revision contains > only the GUP batch size fix. > > Changes in v4: > - Simplify batch clamping logic as suggested by Kiryl > - Don't call GUP functions for an empty batch > - Drop the pinned byte reporting patch since it has been applied to mm-new > > v3: https://lore.kernel.org/all/20260901083452.115365-1-sarthak.sharma@arm.com/ > > mm/gup_test.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/mm/gup_test.c b/mm/gup_test.c > index 185ba3bb8ed1..1b64e932c4c5 100644 > --- a/mm/gup_test.c > +++ b/mm/gup_test.c > @@ -139,11 +139,12 @@ static int __gup_test_ioctl(unsigned int cmd, > if (nr != gup->nr_pages_per_call) > break; > > + nr = min_t(unsigned long, gup->nr_pages_per_call, > + (end - addr) / PAGE_SIZE); > + if (!nr) > + break; Can !nr actually happen? -- Cheers, David