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