+ arm64-make-huge_ptep_get-handled-unaligned-addresses.patch added to mm-new branch

+ arm64-make-huge_ptep_get-handled-unaligned-addresses.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: arm64: make huge_ptep_get handled unaligned addresses
has been added to the -mm mm-new branch.  Its filename is
     arm64-make-huge_ptep_get-handled-unaligned-addresses.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/arm64-make-huge_ptep_get-handled-unaligned-addresses.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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: Dev Jain <dev.jain@arm.com>
Subject: arm64: make huge_ptep_get handled unaligned addresses
Date: Fri, 3 Jul 2026 11:41:54 +0000

Patch series "Fix incorrect access of hugetlb pte entries", v3.

There are various places which use ptep_get() to get the pte entry
corresponding to a hugetlb folio.  Some arches (like s390) have special
handling to compute the pteval, so they provide huge_ptep_get().  Use this
helper consistently.

Additionally, some code paths may provide huge_ptep_get with an unaligned
address.  This is a problem on arm64 (I checked other arches and it looks
fine for them), which is fixed in patch 1.  The fix is made to be
backport-friendly: the cleaner fix would be to perhaps pass the hstate to
huge_ptep_get() - that is wider churn and we can do that later.


This patch (of 6):

huge_ptep_get() can be handed a virtual address pointing to the middle of
a contpmd/contpte mapped hugetlb folio (examples of callers are
pagemap_hugetlb_range, page_mapped_in_vma).

The arm64 helper rewalks the pgtables in find_num_contig to answer whether
the huge pte we have maps a contpmd or a contpte hugetlb folio, and
returns CONT_PMDS or CONT_PTES, so that it can collect a/d bits over the
contiguous ptes.  We can falsely return CONT_PTES instead of CONT_PMDS if
the addr is not aligned.

Fix this by aligning the pmdp pointer down to a contpmd base before
checking equality with the passed huge pte pointer, to correctly answer
whether the huge pte is the base of a contpmd block.

Link: https://lore.kernel.org/20260703114202.365553-1-dev.jain@arm.com
Link: https://lore.kernel.org/20260703114202.365553-2-dev.jain@arm.com
Fixes: 29cb80519689 ("arm64: hugetlb: Cleanup huge_pte size discovery mechanisms")
Signed-off-by: Dev Jain <dev.jain@arm.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Muchun Song <muchun.song@linux.dev>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: Harry Yoo <harry@kernel.org>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Jann Horn <jannh@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Jun'ichi "Nick" Nomura <j-nomura@ce.jp.nec.com>
Cc: Kiryl Shutsemau <kas@kernel.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/arm64/mm/hugetlbpage.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/arm64/mm/hugetlbpage.c~arm64-make-huge_ptep_get-handled-unaligned-addresses
+++ a/arch/arm64/mm/hugetlbpage.c
@@ -87,7 +87,7 @@ static int find_num_contig(struct mm_str
 	p4dp = p4d_offset(pgdp, addr);
 	pudp = pud_offset(p4dp, addr);
 	pmdp = pmd_offset(pudp, addr);
-	if ((pte_t *)pmdp == ptep) {
+	if ((pte_t *)PTR_ALIGN_DOWN(pmdp, sizeof(*pmdp) * CONT_PMDS) == ptep) {
 		*pgsize = PMD_SIZE;
 		return CONT_PMDS;
 	}
_

Patches currently in -mm which might be from dev.jain@arm.com are

mm-swap-rename-subpage-page-in-folio_dup_swap-folio_put_swap.patch
mm-mprotect-drop-sub-from-batching-context.patch
arm64-make-huge_ptep_get-handled-unaligned-addresses.patch
mm-rmap-use-huge_ptep_get-in-try_to_unmap_one.patch
mm-rmap-use-huge_ptep_get-in-try_to_migrate_one.patch
mm-migrate-use-huge_ptep_get-in-remove_migration_pte.patch
mm-page_vma_mapped-use-huge_ptep_get-for-hugetlb.patch
mm-mprotect-use-huge_ptep_get-for-hugetlb.patch