Merge tag 'gcc-plugins-v4.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git...

[cascardo/linux.git] / drivers / char / random.c

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 7274ae8..d6876d5 100644 (file)
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -2100,23 +2100,37 @@ unsigned long get_random_long(void)
 }
 EXPORT_SYMBOL(get_random_long);
 
-/*
- * randomize_range() returns a start address such that
+/**
+ * randomize_page - Generate a random, page aligned address
+ * @start:     The smallest acceptable address the caller will take.
+ * @range:     The size of the area, starting at @start, within which the
+ *             random address must fall.
+ *
+ * If @start + @range would overflow, @range is capped.
  *
- *    [...... <range> .....]
- *  start                  end
+ * NOTE: Historical use of randomize_range, which this replaces, presumed that
+ * @start was already page aligned.  We now align it regardless.
  *
- * a <range> with size "len" starting at the return value is inside in the
- * area defined by [start, end], but is otherwise randomized.
+ * Return: A page aligned address within [start, start + range).  On error,
+ * @start is returned.
  */
 unsigned long
-randomize_range(unsigned long start, unsigned long end, unsigned long len)
+randomize_page(unsigned long start, unsigned long range)
 {
-       unsigned long range = end - len - start;
+       if (!PAGE_ALIGNED(start)) {
+               range -= PAGE_ALIGN(start) - start;
+               start = PAGE_ALIGN(start);
+       }
 
-       if (end <= start + len)
-               return 0;
-       return PAGE_ALIGN(get_random_int() % range + start);
+       if (start > ULONG_MAX - range)
+               range = ULONG_MAX - start;
+
+       range >>= PAGE_SHIFT;
+
+       if (range == 0)
+               return start;
+
+       return start + (get_random_long() % range << PAGE_SHIFT);
 }
 
 /* Interface for in-kernel drivers of true hardware RNGs.