diff options
| -rw-r--r-- | mm/memory.c | 34 |
1 files changed, 30 insertions, 4 deletions
diff --git a/mm/memory.c b/mm/memory.c index 6abc74f41bc0..072139579d89 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3496,10 +3496,36 @@ static vm_fault_t do_fault(struct vm_fault *vmf) struct vm_area_struct *vma = vmf->vma; vm_fault_t ret; - /* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND */ - if (!vma->vm_ops->fault) - ret = VM_FAULT_SIGBUS; - else if (!(vmf->flags & FAULT_FLAG_WRITE)) + /* + * The VMA was not fully populated on mmap() or missing VM_DONTEXPAND + */ + if (!vma->vm_ops->fault) { + /* + * If we find a migration pmd entry or a none pmd entry, which + * should never happen, return SIGBUS + */ + if (unlikely(!pmd_present(*vmf->pmd))) + ret = VM_FAULT_SIGBUS; + else { + vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm, + vmf->pmd, + vmf->address, + &vmf->ptl); + /* + * Make sure this is not a temporary clearing of pte + * by holding ptl and checking again. A R/M/W update + * of pte involves: take ptl, clearing the pte so that + * we don't have concurrent modification by hardware + * followed by an update. + */ + if (unlikely(pte_none(*vmf->pte))) + ret = VM_FAULT_SIGBUS; + else + ret = VM_FAULT_NOPAGE; + + pte_unmap_unlock(vmf->pte, vmf->ptl); + } + } else if (!(vmf->flags & FAULT_FLAG_WRITE)) ret = do_read_fault(vmf); else if (!(vma->vm_flags & VM_SHARED)) ret = do_cow_fault(vmf); |