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 4B0563B14AB; Wed, 14 Oct 2026 08:04:04 +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=1791965045; cv=none; b=b0+JEhpCjNsHJLIg+T0Nzy0/pRAY1Wu+M/Lo24TIeGnudbgsncpijkwG2168Iz0bys+eREamp4sDfzCzTNgMPBvHQAigrx2gAlmDCsaCTP2eWN4WQWtzsMjzgaxf3CaekAr1Uvsx2nJdSRBA5Fkn2g+3ObeTccs19fCvAnoWbww= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791965045; c=relaxed/simple; bh=VUvyoQp7IJ7ge8DNUtWhByz1MCFOiIjd3zBAxfxqntY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=AiH4wgo1Qkn9JVyOraDPxviusOXUFq2GGfRxEPGgUP9VBnnOE4LAZVVIsm65rHD6C64tDi2FvQK6VPoF76E//G8COtkmAPvNOHi/14Z73+YHlIWT4i5es5pHikuPk7DzsaYQRmee9fv90s9+S3+WtRoG/OLnKIprJecY6d02DnA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ai0tDpZ2; 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="ai0tDpZ2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 354451F000FF; Wed, 14 Oct 2026 08:03:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791965044; bh=deXI1eiZdMA+rkrnahrdm835ND51y4e0N1ut/tP+PjI=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ai0tDpZ2EZeG/dvtP+1wHIwzOW7ilCIq0udzFFDkI0sYJoRsijgr1TvQleV8oIaA3 +AI4sbxOlu2cs0No/M/Orymgt3KpM7nYldonsRcxk44/NWct60V6MuWz6ND4fAuUnX sISzo56gQmTUvPta4zKqa+EuKemlpuGcBCG25RAs2jAMRa+n+p2jGXFTk97c7EvyIT X4av0a3nGHqCNa0X2yKZLUtU05RfHB3YdjPAAXtwOoOYWpFg3zaEH/pmgFDqMTRkTw 9nDmaCaukYhgpG7j6rNBn9ByTlt8hoUYpH72HtL/HUqORiIi/+NQOY7NPFlAIGmU3R 7KqMMan2HLljQ== Message-ID: <8d5bbe19-710e-4488-901c-22263ea6797f@kernel.org> Date: Wed, 14 Oct 2026 10:03:57 +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: Barry Song , Kiryl Shutsemau Cc: Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Ying Huang , Baolin Wang , Ryan Roberts , Chuanhua Han , Kyle Zeng , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20261013-folio_pte_scan_range-v1-1-c50dc30bf6ad@kernel.org> 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: 8bit On 10/13/26 15:17, Barry Song wrote: > On Tue, Oct 13, 2026 at 8:57 PM Kiryl Shutsemau wrote: >> >> On Tue, Oct 13, 2026 at 02:30:37PM +0200, 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) >>> --- >>> 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; >> >> These -1/+1 gave me a pause. I guess it is for pmd_end wrapping to 0 in >> the top PMD? A comment would be nice. > > Will pmd_addr_end() make it better? I mean > > upper = pmd_addr_end(address, vma->vm_end); > > nop? I don't like pmd_addr_end(), given the weird semantics: include/asm-generic/pgtable-nopmd.h:#define pmd_addr_end(addr, end) (end) Even if that doesn't apply here, I much rather spell out the boundaries clearly. -- Cheers, David