Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 01f71917 authored by David Hildenbrand's avatar David Hildenbrand Committed by Christian Borntraeger
Browse files

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: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: default avatarDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
parent 5b6c963b

arch/s390/mm/gmap.c

+11 −6
Original line number Diff line number Diff line
@@ -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;

	}