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KVM: s390/mm: try a cow on read only pages for key ops 

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>
Cc: stable@vger.kernel.org
This commit is contained in:
Christian Borntraeger 2014-08-19 16:19:35 +02:00
parent 614a80e474
commit ab3f285f22
1 changed files with 10 additions and 0 deletions
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10
arch/s390/mm/pgtable.c
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@ -986,11 +986,21 @@ 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 |