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Subject[PATCHv5 02/19] mm: Do not use zero page in encrypted pages
Date
Zero page is not encrypted and putting it into encrypted VMA produces
garbage.

We can map zero page with KeyID-0 into an encrypted VMA, but this would
be violation security boundary between encryption domains.

Forbid zero pages in encrypted VMAs.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
arch/s390/include/asm/pgtable.h | 2 +-
include/linux/mm.h | 4 ++--
mm/huge_memory.c | 3 +--
mm/memory.c | 3 +--
4 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 5ab636089c60..2e8658962aae 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -505,7 +505,7 @@ static inline int mm_alloc_pgste(struct mm_struct *mm)
* In the case that a guest uses storage keys
* faults should no longer be backed by zero pages
*/
-#define mm_forbids_zeropage mm_has_pgste
+#define vma_forbids_zeropage(vma) mm_has_pgste(vma->vm_mm)
static inline int mm_uses_skeys(struct mm_struct *mm)
{
#ifdef CONFIG_PGSTE
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c8780c5835ad..151d6e6b16e5 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -92,8 +92,8 @@ extern int mmap_rnd_compat_bits __read_mostly;
* s390 does this to prevent multiplexing of hardware bits
* related to the physical page in case of virtualization.
*/
-#ifndef mm_forbids_zeropage
-#define mm_forbids_zeropage(X) (0)
+#ifndef vma_forbids_zeropage
+#define vma_forbids_zeropage(vma) vma_keyid(vma)
#endif

/*
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1cd7c1a57a14..83f096c7299b 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -676,8 +676,7 @@ int do_huge_pmd_anonymous_page(struct vm_fault *vmf)
return VM_FAULT_OOM;
if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
return VM_FAULT_OOM;
- if (!(vmf->flags & FAULT_FLAG_WRITE) &&
- !mm_forbids_zeropage(vma->vm_mm) &&
+ if (!(vmf->flags & FAULT_FLAG_WRITE) && !vma_forbids_zeropage(vma) &&
transparent_hugepage_use_zero_page()) {
pgtable_t pgtable;
struct page *zero_page;
diff --git a/mm/memory.c b/mm/memory.c
index 02fbef2bd024..a705637d2ded 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3139,8 +3139,7 @@ static int do_anonymous_page(struct vm_fault *vmf)
return 0;

/* Use the zero-page for reads */
- if (!(vmf->flags & FAULT_FLAG_WRITE) &&
- !mm_forbids_zeropage(vma->vm_mm)) {
+ if (!(vmf->flags & FAULT_FLAG_WRITE) && !vma_forbids_zeropage(vma)) {
entry = pte_mkspecial(pfn_pte(my_zero_pfn(vmf->address),
vma->vm_page_prot));
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
--
2.18.0
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