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s390/mm: don't fault everything in read-write in gmap_pte_op_fixup() 

Let's not fault in everything in read-write but limit it to read-only
where possible.

When restricting access rights, we already have the required protection
level in our hands. When reading from guest 2 storage (gmap_read_table),
it is obviously PROT_READ. When shadowing a pte, the required protection
level is given via the guest 2 provided pte.

Based on an initial patch by Martin Schwidefsky.

Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
This commit is contained in:
David Hildenbrand 2016-06-13 10:49:04 +02:00 committed by Christian Borntraeger
parent 5b6c963bce
commit 01f719176f
1 changed files with 11 additions and 6 deletions
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17
arch/s390/mm/gmap.c
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@ -811,19 +811,22 @@ static pte_t *gmap_pte_op_walk(struct gmap *gmap, unsigned long gaddr,
* @gmap: pointer to guest mapping meta data structure
* @gaddr: virtual address in the guest address space
* @vmaddr: address in the host process address space
* @prot: indicates access rights: PROT_NONE, PROT_READ or PROT_WRITE
*
* Returns 0 if the caller can retry __gmap_translate (might fail again),
* -ENOMEM if out of memory and -EFAULT if anything goes wrong while fixing
* up or connecting the gmap page table.
*/
static int gmap_pte_op_fixup(struct gmap *gmap, unsigned long gaddr,
unsigned long vmaddr)
unsigned long vmaddr, int prot)
{
struct mm_struct *mm = gmap->mm;
unsigned int fault_flags;
bool unlocked = false;
BUG_ON(gmap_is_shadow(gmap));
if (fixup_user_fault(current, mm, vmaddr, FAULT_FLAG_WRITE, &unlocked))
fault_flags = (prot == PROT_WRITE) ? FAULT_FLAG_WRITE : 0;
if (fixup_user_fault(current, mm, vmaddr, fault_flags, &unlocked))
return -EFAULT;
if (unlocked)
/* lost mmap_sem, caller has to retry __gmap_translate */
@ -875,7 +878,7 @@ static int gmap_protect_range(struct gmap *gmap, unsigned long gaddr,
vmaddr = __gmap_translate(gmap, gaddr);
if (IS_ERR_VALUE(vmaddr))
return vmaddr;
rc = gmap_pte_op_fixup(gmap, gaddr, vmaddr);
rc = gmap_pte_op_fixup(gmap, gaddr, vmaddr, prot);
if (rc)
return rc;
continue;
@ -957,7 +960,7 @@ int gmap_read_table(struct gmap *gmap, unsigned long gaddr, unsigned long *val)
rc = vmaddr;
break;
}
rc = gmap_pte_op_fixup(gmap, gaddr, vmaddr);
rc = gmap_pte_op_fixup(gmap, gaddr, vmaddr, PROT_READ);
if (rc)
break;
}
@ -1041,7 +1044,7 @@ static int gmap_protect_rmap(struct gmap *sg, unsigned long raddr,
radix_tree_preload_end();
if (rc) {
kfree(rmap);
rc = gmap_pte_op_fixup(parent, paddr, vmaddr);
rc = gmap_pte_op_fixup(parent, paddr, vmaddr, prot);
if (rc)
return rc;
continue;
@ -1910,10 +1913,12 @@ int gmap_shadow_page(struct gmap *sg, unsigned long saddr, pte_t pte)
unsigned long vmaddr, paddr;
spinlock_t *ptl;
pte_t *sptep, *tptep;
int prot;
int rc;
BUG_ON(!gmap_is_shadow(sg));
parent = sg->parent;
prot = (pte_val(pte) & _PAGE_PROTECT) ? PROT_READ : PROT_WRITE;
rmap = kzalloc(sizeof(*rmap), GFP_KERNEL);
if (!rmap)
@ -1955,7 +1960,7 @@ int gmap_shadow_page(struct gmap *sg, unsigned long saddr, pte_t pte)
radix_tree_preload_end();
if (!rc)
break;
rc = gmap_pte_op_fixup(parent, paddr, vmaddr);
rc = gmap_pte_op_fixup(parent, paddr, vmaddr, prot);
if (rc)
break;
}