From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1DA233E49D7; Wed, 14 Oct 2026 08:02:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791964967; cv=none; b=Hhosz5kGtOHhkuagT2bmXiHVqvYBTe8ZdcyLbrZjf71ArbSboJL3WV6Xe6S5tmeI3YVTIYKIndyXbCGkOACktSH2oZXbGgP/sPiCULBFEE48xAf12UXbuoMgv3Ey2CxgRxhrjiLHlousYyY9oeGBLX2NzhbAAEndfF+zJTxI0YA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791964967; c=relaxed/simple; bh=Yr69TYQ1d0AFWM2Gb8YkcUc2SOI95OB7n5BdwoVlArQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pwQe009LP5zDgc7qQQ8G7+8HDa5JaiyBUqBOLcL9mJ5ya1hGmgxm88/3Qx8zJE+RPKK+xXyqVN2xz7e/n08/e/l/hHNe6pOk6KNLwBLFRVHBLtPz96iv+huu7Xvn7ih8bCOEzgwo6OM3LIQ+aZWSHk4n/rO1XYUwF1bKotg1A74= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HBpdrmSu; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HBpdrmSu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A41CD1F000FF; Wed, 14 Oct 2026 08:02:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791964965; bh=X9ytMwqCWIzw05HboKv/lmzrNih4neXNeq84eInfJtw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=HBpdrmSuw1yhtNos3sT9tV91CknmD7XQmyevZJ2kCvLr9wL4Ai7tkicw8qI3xv88b WcGTwbsyvZjeXWw8Tt1CIgz99OdwOUzSskNkuWPT2J4HuUlOhCu22SH991wQJRkeUB JmmBAaVOFoQwJNoUzQjbofuUe1Esyw80tPOtyEzj56RMbdFZlPWuoto6Y0uJTaG85l fBFmF2xPxHBAsI68U9XRMUQuVNyw12y9NCl6CsZvodMpCXbONKufSOU2jOfyQ5dkOL aytwcAT4mgsn/uGjeMeJG3qvYL24Rbw9tqsfxUR0sezq+tQ7nsYttUzCLc0Rlgx+W/ H2J5w58k0XqOw== Message-ID: Date: Wed, 14 Oct 2026 10:02:38 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: fix address wraparound when scanning large folio PTEs To: Baolin Wang , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Ying Huang , Barry Song , Ryan Roberts , Chuanhua Han , Kiryl Shutsemau , Kyle Zeng Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20261013-folio_pte_scan_range-v1-1-c50dc30bf6ad@kernel.org> <5848db18-9de3-437b-9967-162ced4f8cb9@linux.alibaba.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: <5848db18-9de3-437b-9967-162ced4f8cb9@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 10/14/26 08:02, Baolin Wang wrote: > > > On 10/13/26 8:30 PM, David Hildenbrand (Arm) wrote: >> numa_rebuild_large_mapping() and do_swap_page() can be tricked into >> generating an address wraparound, crashing the kernel. All that's required >> is to map a tail page of a large folio close enough to the start/end of >> the address space to e.g., make >> >>     unsigned long addr_start = addr - (nr << PAGE_SHIFT); >> >> to wrap around. >> >> Let's fix it by providing a better helper, folio_pte_scan_range(), that >> takes care of staying within VMA and page table boundaries while >> handling possible wraparounds. >> >> Reported-by: Kyle Zeng >> Fixes: d2136d749d76 ("mm: support multi-size THP numa balancing") >> Fixes: 508758960b8d ("mm: swap: entirely map large folios found in swapcache") >> Cc: stable@vger.kernel.org >> Signed-off-by: David Hildenbrand (Arm) >> --- > > Thanks for the fix. > >>   mm/memory.c | 43 +++++++++++++++++++++++++++++-------------- >>   1 file changed, 29 insertions(+), 14 deletions(-) >> >> diff --git a/mm/memory.c b/mm/memory.c >> index 1f5d5f7d39cd2..a3823010aa981 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -4933,6 +4933,27 @@ static void check_swap_exclusive(struct folio *folio, >> swp_entry_t entry, >>       } while (--nr_pages); >>   } >>   +/* >> + * Get the address range in which a folio might be mapped, assuming its pages >> + * are mapped consecutively and the folio page at the given idx is mapped at >> + * the given address. >> + */ >> +static void folio_pte_scan_range(const struct folio *folio, >> +        const struct vm_area_struct *vma, unsigned long addr, >> +        unsigned long idx, unsigned long *start, unsigned long *end) >> +{ >> +    /* Stay within the page table and VMA boundaries. */ >> +    const unsigned long pmd_start = addr & PMD_MASK; >> +    const unsigned long pmd_end = pmd_start + PMD_SIZE; >> +    const unsigned long lower = max(pmd_start, vma->vm_start); >> +    const unsigned long upper = min(pmd_end - 1, vma->vm_end - 1) + 1; > > I also agree with Barry and Lorenzo's suggestion to use the more readable > pmd_addr_end() helper. I had that, then I found that for folded page tables it does something rather odd, which made me assume "this is not better at all". -- Cheers, David