1 files changed, 12 insertions, 1 deletions

diff --git a/fs/dax.c b/fs/dax.c
index 7ae6df7ea1d2..bcfb14bfc1e4 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -569,8 +569,20 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
         if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
                 goto fallback;
 
+        sector = bh.b_blocknr << (blkbits - 9);
+
         if (buffer_unwritten(&bh) || buffer_new(&bh)) {
                 int i;
+
+                length = bdev_direct_access(bh.b_bdev, sector, &kaddr, &pfn,
+                                                bh.b_size);
+                if (length < 0) {
+                        result = VM_FAULT_SIGBUS;
+                        goto out;
+                }
+                if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR))
+                        goto fallback;
+
                 for (i = 0; i < PTRS_PER_PMD; i++)
                         clear_pmem(kaddr + i * PAGE_SIZE, PAGE_SIZE);
                 wmb_pmem();
@@ -623,7 +635,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
                 result = VM_FAULT_NOPAGE;
                 spin_unlock(ptl);
         } else {
-                sector = bh.b_blocknr << (blkbits - 9);
                 length = bdev_direct_access(bh.b_bdev, sector, &kaddr, &pfn,
                                                 bh.b_size);
                 if (length < 0) {