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 5B82038C2A0; Mon, 2 Mar 2026 20:50:47 +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=1772484648; cv=none; b=je9O/ZQWmignDYNDgqHeG6EG28D4rKa4c+PAB8soGGX2BTljc0fgenVDtgAye/fhfQ8D10F5/iX3D+pYiyDNX5W2PfDwjNEY801Y4XwRN0ZQqLTy/4qEMPb+swxQ7hn8xhMunkGNH7ZRRLqoPGw7cImwOxb08GnhLf5VZ/4ARK0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772484648; c=relaxed/simple; bh=pCLHO0vnQiSXr/GSP2+voEAuCidxHvmeIhB2m/IisHs=; h=Date:To:From:Subject:Message-Id; b=MqLqajV/rekDJWe1niQ1OKm8Z9Yd0U+82grydNeOMYj95PScuNZhh9qrKlQnaYWXPhTSasSyd+UuqCkW0CXuEbLEWAybDeQ4xs5Imo8xVH++ljk1C+5Z0gPH72FIIJdB0NdJMxJJYF3S4km+SJ8Y9d2w78GeFMSe12YXlqB8bIc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=CgPkmcCQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="CgPkmcCQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A54B7C19425; Mon, 2 Mar 2026 20:50:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1772484647; bh=pCLHO0vnQiSXr/GSP2+voEAuCidxHvmeIhB2m/IisHs=; h=Date:To:From:Subject:From; b=CgPkmcCQhXBI+a9KVqhec9owuSTntaLGCod+2L2hODJDFpZkJCFC6CXpnoA02DGwj cCHUSUKBkbhl/brKQeCkCq6AMZYYLqA/kOfFTaPQ1DwNssFNNcLHnXz7GV19zui9zL vsTKJ/Qs4hFWKZe5Upq28cDAQO3wm1w9aO4TFpjI= Date: Mon, 02 Mar 2026 12:50:46 -0800 To: mm-commits@vger.kernel.org,ziy@nvidia.com,willy@infradead.org,surenb@google.com,stable@vger.kernel.org,ryan.roberts@arm.com,rppt@kernel.org,npache@redhat.com,liam.howlett@oracle.com,lance.yang@linux.dev,dev.jain@arm.com,david@kernel.org,baolin.wang@linux.alibaba.com,baohua@kernel.org,lorenzo.stoakes@oracle.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-huge_memory-fix-memory-corruption-on-huge-zero-page-move.patch added to mm-hotfixes-unstable branch Message-Id: <20260302205047.A54B7C19425@smtp.kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/huge_memory: fix memory corruption on huge zero page move has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-huge_memory-fix-memory-corruption-on-huge-zero-page-move.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-huge_memory-fix-memory-corruption-on-huge-zero-page-move.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Lorenzo Stoakes Subject: mm/huge_memory: fix memory corruption on huge zero page move Date: Mon, 2 Mar 2026 17:06:19 +0000 In commit eb1521dad8f3 ("userfaultfd: handle zeropage moves by UFFDIO_MOVE"), handling was added to enable the moving of huge zero pages in move_pages_huge_pmd(). This achieves this by setting src_folio to NULL, and adding subsequent checks for src_folio being NULL to determine whether to perform the usual move operations or to simply establish the huge zero page in the destination. As part of this change, when installing the destination huge zero page it invoked mk_huge_pmd() on src_page, correctly. However, commit e3981db444a0 ("mm: add folio_mk_pmd()") updated the code in the huge zero page branch from mk_huge_pmd(src_page, ...) to folio_mk_pmd(src_folio, ...), where src_folio is guaranteed to be NULL at this point. This resulted in an invocation of folio_mk_pmd(NULL, ...) in effect, which causes an invocation of page_to_pfn(0) and results in the installation of a corrupted PMD entry and undefined behaviour. This patch fixes the issue by obtaining the zero folio via page_folio(src_page) and feeding this into folio_mk_pmd(). This retains the use of folio_mk_pmd() whilst avoiding the memory corruption. Additionally, this code path was not updated to reflect the changes introduced by commit d82d09e48219 ("mm/huge_memory: mark PMD mappings of the huge zero folio special"), meaning a zero huge folio was installed but not marked special in this case. This patch additionally fixes that issue by invoking pmd_mkspecial(). With thanks to Chris Down who exposed this bug by adding an explicit test for UFFDIO_MOVE in commit f07254dce67d ("selftests/mm: add UFFDIO_MOVE huge zeropage PMD regression test"). Link: https://lkml.kernel.org/r/20260302170619.867056-1-lorenzo.stoakes@oracle.com Fixes: e3981db444a0 ("mm: add folio_mk_pmd()") Signed-off-by: Lorenzo Stoakes Cc: Baolin Wang Cc: Barry Song Cc: David Hildenbrand Cc: Dev Jain Cc: Lance Yang Cc: Liam Howlett Cc: Matthew Wilcox (Oracle) Cc: Mike Rapoport Cc: Nico Pache Cc: Ryan Roberts Cc: Suren Baghdasaryan Cc: Zi Yan Cc: Signed-off-by: Andrew Morton --- mm/huge_memory.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/mm/huge_memory.c~mm-huge_memory-fix-memory-corruption-on-huge-zero-page-move +++ a/mm/huge_memory.c @@ -2796,8 +2796,12 @@ int move_pages_huge_pmd(struct mm_struct /* Follow mremap() behavior and treat the entry dirty after the move */ _dst_pmd = pmd_mkwrite(pmd_mkdirty(_dst_pmd), dst_vma); } else { + struct folio *zero_folio = page_folio(src_page); + + VM_WARN_ON_ONCE_FOLIO(!is_huge_zero_folio(zero_folio), zero_folio); src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd); - _dst_pmd = folio_mk_pmd(src_folio, dst_vma->vm_page_prot); + _dst_pmd = folio_mk_pmd(zero_folio, dst_vma->vm_page_prot); + _dst_pmd = pmd_mkspecial(_dst_pmd); } set_pmd_at(mm, dst_addr, dst_pmd, _dst_pmd); _ Patches currently in -mm which might be from lorenzo.stoakes@oracle.com are mm-huge_memory-fix-memory-corruption-on-huge-zero-page-move.patch