Fix up mmap of /dev/kmem

This leaves the issue of whether we should deprecate the whole thing (or
if we should check the whole mmap range, for that matter) open. Just do
the minimal fix for now.

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 42187381506b7d0ff45dcdcc4df5dc2be7a2867f..850a78c9c4bc9c639dd5b2c5816a4c89e7568eb1 100644 (file)
--- 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);
 }