Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

[linux.git] / mm / memory.c

diff --git a/mm/memory.c b/mm/memory.c
index 6abc74f41bc0b6d2f9b7210fd102c927178f9616..4ad2d293ddc2605d2ae44ce075de68beb93841e0 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1537,10 +1537,15 @@ static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr,
                         * in may not match the PFN we have mapped if the
                         * mapped PFN is a writeable COW page.  In the mkwrite
                         * case we are creating a writable PTE for a shared
-                        * mapping and we expect the PFNs to match.
+                        * mapping and we expect the PFNs to match. If they
+                        * don't match, we are likely racing with block
+                        * allocation and mapping invalidation so just skip the
+                        * update.
                         */
-                       if (WARN_ON_ONCE(pte_pfn(*pte) != pfn_t_to_pfn(pfn)))
+                       if (pte_pfn(*pte) != pfn_t_to_pfn(pfn)) {
+                               WARN_ON_ONCE(!is_zero_pfn(pte_pfn(*pte)));
                                goto out_unlock;
+                       }
                        entry = *pte;
                        goto out_mkwrite;
                } else
@@ -3496,10 +3501,36 @@ 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);