[merged mm-stable] mm-disallow-raw-pfn-mappings-of-huge-shared-zeropage.patch removed from -mm tree

[merged mm-stable] mm-disallow-raw-pfn-mappings-of-huge-shared-zeropage.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm: disallow raw PFN mappings of huge/shared zeropage
has been removed from the -mm tree.  Its filename was
     mm-disallow-raw-pfn-mappings-of-huge-shared-zeropage.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Lance Yang <lance.yang@linux.dev>
Subject: mm: disallow raw PFN mappings of huge/shared zeropage
Date: Mon, 21 Sep 2026 13:42:25 +0800

Handling the huge/shared zeropage correctly in vmf_insert_pfn_pmd() and
vmf_insert_pfn_prot() is more involved.  We would need to check whether
the VMA allows it and keep the mapping read-only, similar to the checks in
vm_mixed_ok().

No in-tree user needs that support, so reject these mappings with
VM_FAULT_SIGBUS rather than complicate the code for now.

Link: https://lore.kernel.org/20260921054225.28537-1-lance.yang@linux.dev
Link: https://lore.kernel.org/all/20260917121010.60966-1-lance.yang@linux.dev/
Signed-off-by: Lance Yang <lance.yang@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Liam Howlett <liam@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Mike Rapoport (IBM)" <rppt@kernel.org>
Cc: Nico Pache (Red Hat) <nico.pache@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Usama Arif <usama.arif@linux.dev>
Cc: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
---

 mm/huge_memory.c |    3 +++
 mm/memory.c      |    3 +++
 2 files changed, 6 insertions(+)

--- a/mm/huge_memory.c~mm-disallow-raw-pfn-mappings-of-huge-shared-zeropage
+++ a/mm/huge_memory.c
@@ -1727,6 +1727,9 @@ vm_fault_t vmf_insert_pfn_pmd(struct vm_
 						(VM_PFNMAP|VM_MIXEDMAP));
 	BUG_ON((vma->vm_flags & VM_PFNMAP) && vma_is_cow_mapping(vma));
 
+	if (unlikely(is_huge_zero_pfn(pfn)))
+		return VM_FAULT_SIGBUS;
+
 	pfnmap_setup_cachemode_pfn(pfn, &pgprot);
 
 	return insert_pmd(vma, addr, vmf->pmd, fop, pgprot, write);
--- a/mm/memory.c~mm-disallow-raw-pfn-mappings-of-huge-shared-zeropage
+++ a/mm/memory.c
@@ -2860,6 +2860,9 @@ vm_fault_t vmf_insert_pfn_prot(struct vm
 	BUG_ON((vma->vm_flags & VM_PFNMAP) && vma_is_cow_mapping(vma));
 	BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
 
+	if (unlikely(is_zero_pfn(pfn)))
+		return VM_FAULT_SIGBUS;
+
 	if (addr < vma->vm_start || addr >= vma->vm_end)
 		return VM_FAULT_SIGBUS;
 
_

Patches currently in -mm which might be from lance.yang@linux.dev are