Patch "s390/mm: validate VMA in PGSTE manipulation functions" has been added to the 4.14-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    s390/mm: validate VMA in PGSTE manipulation functions

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     s390-mm-validate-vma-in-pgste-manipulation-functions.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit b9eaebec12377e206c0c9ed092464987a81c2dfd
Author: David Hildenbrand <david@xxxxxxxxxx>
Date:   Thu Sep 9 18:22:42 2021 +0200

    s390/mm: validate VMA in PGSTE manipulation functions
    
    [ Upstream commit fe3d10024073f06f04c74b9674bd71ccc1d787cf ]
    
    We should not walk/touch page tables outside of VMA boundaries when
    holding only the mmap sem in read mode. Evil user space can modify the
    VMA layout just before this function runs and e.g., trigger races with
    page table removal code since commit dd2283f2605e ("mm: mmap: zap pages
    with read mmap_sem in munmap"). gfn_to_hva() will only translate using
    KVM memory regions, but won't validate the VMA.
    
    Further, we should not allocate page tables outside of VMA boundaries: if
    evil user space decides to map hugetlbfs to these ranges, bad things will
    happen because we suddenly have PTE or PMD page tables where we
    shouldn't have them.
    
    Similarly, we have to check if we suddenly find a hugetlbfs VMA, before
    calling get_locked_pte().
    
    Fixes: 2d42f9477320 ("s390/kvm: Add PGSTE manipulation functions")
    Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
    Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
    Acked-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20210909162248.14969-4-david@xxxxxxxxxx
    Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index ae677f814bc07..a2182d5a1a105 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -896,6 +896,7 @@ EXPORT_SYMBOL(get_guest_storage_key);
 int pgste_perform_essa(struct mm_struct *mm, unsigned long hva, int orc,
 			unsigned long *oldpte, unsigned long *oldpgste)
 {
+	struct vm_area_struct *vma;
 	unsigned long pgstev;
 	spinlock_t *ptl;
 	pgste_t pgste;
@@ -905,6 +906,10 @@ int pgste_perform_essa(struct mm_struct *mm, unsigned long hva, int orc,
 	WARN_ON_ONCE(orc > ESSA_MAX);
 	if (unlikely(orc > ESSA_MAX))
 		return -EINVAL;
+
+	vma = vma_lookup(mm, hva);
+	if (!vma || is_vm_hugetlb_page(vma))
+		return -EFAULT;
 	ptep = get_locked_pte(mm, hva, &ptl);
 	if (unlikely(!ptep))
 		return -EFAULT;
@@ -997,10 +1002,14 @@ EXPORT_SYMBOL(pgste_perform_essa);
 int set_pgste_bits(struct mm_struct *mm, unsigned long hva,
 			unsigned long bits, unsigned long value)
 {
+	struct vm_area_struct *vma;
 	spinlock_t *ptl;
 	pgste_t new;
 	pte_t *ptep;
 
+	vma = vma_lookup(mm, hva);
+	if (!vma || is_vm_hugetlb_page(vma))
+		return -EFAULT;
 	ptep = get_locked_pte(mm, hva, &ptl);
 	if (unlikely(!ptep))
 		return -EFAULT;
@@ -1025,9 +1034,13 @@ EXPORT_SYMBOL(set_pgste_bits);
  */
 int get_pgste(struct mm_struct *mm, unsigned long hva, unsigned long *pgstep)
 {
+	struct vm_area_struct *vma;
 	spinlock_t *ptl;
 	pte_t *ptep;
 
+	vma = vma_lookup(mm, hva);
+	if (!vma || is_vm_hugetlb_page(vma))
+		return -EFAULT;
 	ptep = get_locked_pte(mm, hva, &ptl);
 	if (unlikely(!ptep))
 		return -EFAULT;