1 files changed, 8 insertions, 4 deletions

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 42187381506b..850a78c9c4bc 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -261,7 +261,11 @@ static int mmap_mem(struct file * file, struct vm_area_struct * vma)
 
 static int mmap_kmem(struct file * file, struct vm_area_struct * vma)
 {
-        unsigned long long val;
+        unsigned long pfn;
+
+        /* Turn a kernel-virtual address into a physical page frame */
+        pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;
+
         /*
          * RED-PEN: on some architectures there is more mapped memory
          * than available in mem_map which pfn_valid checks
@@ -269,10 +273,10 @@ static int mmap_kmem(struct file * file, struct vm_area_struct * vma)
          *
          * RED-PEN: vmalloc is not supported right now.
          */
-        if (!pfn_valid(vma->vm_pgoff))
+        if (!pfn_valid(pfn))
                 return -EIO;
-        val = (u64)vma->vm_pgoff << PAGE_SHIFT;
-        vma->vm_pgoff = __pa(val) >> PAGE_SHIFT;
+
+        vma->vm_pgoff = pfn;
         return mmap_mem(file, vma);
 }