X-Git-Url: http://git.cascardo.eti.br/?a=blobdiff_plain;f=drivers%2Fchar%2Frandom.c;h=d6876d50622075f1b490bf7a19831b4e8784adb6;hb=9ffc66941df278c9f4df979b6bcf6c6ddafedd16;hp=7274ae89ddb39f3450ac9f56ef64db6384330497;hpb=0766f788eb727e2e330d55d30545db65bcf2623f;p=cascardo%2Flinux.git

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 7274ae89ddb3..d6876d506220 100644
--- 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.