1 files changed, 14 insertions, 3 deletions

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 8fe1b0aa2896..b9a254dcc0e7 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -108,6 +108,16 @@ static void huge_pagevec_release(struct pagevec *pvec)
         pagevec_reinit(pvec);
 }
 
+/*
+ * Mask used when checking the page offset value passed in via system
+ * calls.  This value will be converted to a loff_t which is signed.
+ * Therefore, we want to check the upper PAGE_SHIFT + 1 bits of the
+ * value.  The extra bit (- 1 in the shift value) is to take the sign
+ * bit into account.
+ */
+#define PGOFF_LOFFT_MAX \
+        (((1UL << (PAGE_SHIFT + 1)) - 1) <<  (BITS_PER_LONG - (PAGE_SHIFT + 1)))
+
 static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
 {
         struct inode *inode = file_inode(file);
@@ -127,12 +137,13 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
         vma->vm_ops = &hugetlb_vm_ops;
 
         /*
-         * Offset passed to mmap (before page shift) could have been
-         * negative when represented as a (l)off_t.
+         * page based offset in vm_pgoff could be sufficiently large to
+         * overflow a (l)off_t when converted to byte offset.
          */
-        if (((loff_t)vma->vm_pgoff << PAGE_SHIFT) < 0)
+        if (vma->vm_pgoff & PGOFF_LOFFT_MAX)
                 return -EINVAL;
 
+        /* must be huge page aligned */
         if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT))
                 return -EINVAL;