From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 7DFA8282F05 for ; Tue, 3 Mar 2026 08:49:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772527762; cv=none; b=uUa6ufN9CDzLyKyFfJTivdYYXFYbO/BkeBa6J83/RDnnbQoveDqS3mFXASjbqrLPiGqrHhbhQeZONDiekSQ2jMcC/vlBBfilXtr5Kipu6XTaqPDTT8yNKnPYmpXhNGB5C+tABXIRAbLk90zJRtst7btjtLBGQq0q9CKsCGN6a80= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772527762; c=relaxed/simple; bh=JaD79dXQHufCQnM1pCE8hYRquoIOvY5KaE/X/JmRPFU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=G/hpKjasiBfLjWeGdL3virKJKVxTKFhada4pbSjdUZVtLY6mse/+hg/SDqQhp2boXefMWz0CkXAH6xtFwqRjQK5y3G0WfGl7le+T3Klcd3sd1Z06EttgGLDm2WdBhUsaWoMLl7hFcjhaoQc1/Yd1H0phY4cdKA8HrIQD36Gbwwo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=J/72Vv2c; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="J/72Vv2c" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A0B26C116C6; Tue, 3 Mar 2026 08:49:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772527762; bh=JaD79dXQHufCQnM1pCE8hYRquoIOvY5KaE/X/JmRPFU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=J/72Vv2cjiRCjXUsiQrPB1gIu96TS7IExQyAgZolreyw41sVbQb0G+pb+PBfOUyO4 BT4v9iTvSH/1Cb7uCZ7tgNLFRH8Zdt48mm4ctlT9ezNtMH0fTTFa+YTAsWrcknEJJ7 Jn+VvKYIRQHCAfHwqRhKo5sgm3LUm63RcoLE46XcMa2fIanDS3kHAl2NZ64dALZuCu VGKIPNo/gkkcfkzhXlk1BfJNI9Au3hJQ2Gsp4BRwvI5n9TWDGiRSmOrVMmEMFsB9D0 6q9jBIAtgAuB69Xa1Qxm6OcYw/K45SosrJZ1xTvfMQKxBZforaU4xKB9IYSacKcsi5 b3dSX3KC2vWmQ== Message-ID: Date: Tue, 3 Mar 2026 09:49:16 +0100 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-hotfixes] mm/huge_memory: fix memory corruption on huge zero page move To: Lorenzo Stoakes , Andrew Morton Cc: Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Matthew Wilcox , Chris Down , Suren Baghdasaryan , Mike Rapoport , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260302170619.867056-1-lorenzo.stoakes@oracle.com> <901fec30-c5c2-46c5-b48d-f9a8f5e5c928@kernel.org> <20260302125032.313797b0ec908cd133f3ed82@linux-foundation.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: 7bit On 3/3/26 08:25, Lorenzo Stoakes wrote: > On Mon, Mar 02, 2026 at 12:50:32PM -0800, Andrew Morton wrote: >> On Mon, 2 Mar 2026 17:19:15 +0000 Lorenzo Stoakes wrote: >> >>> >>> Yup, if people would actually cc the right people I'd not have wasted my >>> afternoon. >>> >>> Replying there. >>> >> >> I'm not sure where this is headed but I'll queue this patch for now, to >> get it some testing, to lessen duplicated bug reports and to generally track things. > > Hi Andrew - > > We should drop my patch and take Chris's. > > However, life isn't so simple :) as there's been some confusion with his series > since his email client seemed to mess up somehow and a couple patches need to be > squashed on one another. > > So to make life easier, I enclose a squashed patch (combining the commit > message from both), with my R-b, T-b tags attached, please replace my patch > with this one. > > Also, could you make this into a 2 patch series with > https://lore.kernel.org/linux-mm/aaBWG4fajXXbjpVN@chrisdown.name/ _after_ this > one? > > mm-unstable (I'm not sure why we're rushing changes there so quick...) had > _only_ this regression test patch in it, so we were left with a kernel that > splatted on running mm selftests, which is not what we want. > > (It seems to me this is what mm-new is for, and it seems we have some holes in > our testing still since this got thorugh). > > Please drop the patch you have for this already in mm-unstable and make sure we > only have it _after_ the fix is applied :) > > Thanks, Lorenzo > > ----8<---- > From fbabbc38c000308d2c621a4b3ec1f4bca1d71c1d Mon Sep 17 00:00:00 2001 > From: Chris Down > Date: Tue, 3 Mar 2026 07:21:21 +0000 > Subject: [PATCH] mm/huge_memory: Fix use of NULL folio in > move_pages_huge_pmd() > > move_pages_huge_pmd() handles UFFDIO_MOVE for both normal THPs and huge > zero pages. For the huge zero page path, src_folio is explicitly set to > NULL, and is used as a sentinel to skip folio operations like lock and > rmap. > > In the huge zero page branch, src_folio is NULL, so folio_mk_pmd(NULL, > pgprot) passes NULL through folio_pfn() and page_to_pfn(). With > SPARSEMEM_VMEMMAP this silently produces a bogus PFN, installing a PMD > pointing to non-existent physical memory. On other memory models it is a > NULL dereference. > > Use page_folio(src_page) to obtain the valid huge zero folio from the > page, which was obtained from pmd_page() and remains valid throughout. > > After commit d82d09e48219 ("mm/huge_memory: mark PMD mappings of the > huge zero folio special"), moved huge zero PMDs must remain special so > vm_normal_page_pmd() continues to treat them as special mappings. > > move_pages_huge_pmd() currently reconstructs the destination PMD in the > huge zero page branch, which drops PMD state such as pmd_special() on > architectures with CONFIG_ARCH_HAS_PTE_SPECIAL. As a result, > vm_normal_page_pmd() can treat the moved huge zero PMD as a normal page > and corrupt its refcount. > > Instead of reconstructing the PMD from the folio, derive the destination > entry from src_pmdval after pmdp_huge_clear_flush(), then handle the PMD > metadata the same way move_huge_pmd() does for moved entries by marking > it soft-dirty and clearing uffd-wp. > > Fixes: e3981db444a0 ("mm: add folio_mk_pmd()") > Cc: stable@vger.kernel.org > Reviewed-by: Lorenzo Stoakes > Tested-by: Lorenzo Stoakes > Signed-off-by: Chris Down > --- Acked-by: David Hildenbrand (Arm) -- Cheers, David