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    Subject[PATCH 3.13 079/103] KVM: s390/mm: try a cow on read only pages for key ops
    Date
    3.13.11.8 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Christian Borntraeger <borntraeger@de.ibm.com>

    commit ab3f285f227fec62868037e9b1b1fd18294a83b8 upstream.

    The PFMF instruction handler blindly wrote the storage key even if
    the page was mapped R/O in the host. Lets try a COW before continuing
    and bail out in case of errors.

    Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
    Reviewed-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    arch/s390/mm/pgtable.c | 10 ++++++++++
    1 file changed, 10 insertions(+)

    diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
    index e794c88..9cffb96 100644
    --- a/arch/s390/mm/pgtable.c
    +++ b/arch/s390/mm/pgtable.c
    @@ -810,11 +810,21 @@ int set_guest_storage_key(struct mm_struct *mm, unsigned long addr,
    pte_t *ptep;

    down_read(&mm->mmap_sem);
    +retry:
    ptep = get_locked_pte(current->mm, addr, &ptl);
    if (unlikely(!ptep)) {
    up_read(&mm->mmap_sem);
    return -EFAULT;
    }
    + if (!(pte_val(*ptep) & _PAGE_INVALID) &&
    + (pte_val(*ptep) & _PAGE_PROTECT)) {
    + pte_unmap_unlock(*ptep, ptl);
    + if (fixup_user_fault(current, mm, addr, FAULT_FLAG_WRITE)) {
    + up_read(&mm->mmap_sem);
    + return -EFAULT;
    + }
    + goto retry;
    + }

    new = old = pgste_get_lock(ptep);
    pgste_val(new) &= ~(PGSTE_GR_BIT | PGSTE_GC_BIT |
    --
    1.9.1


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