Merge tag 'fsverity-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt

[linux-2.6-microblaze.git] / mm / util.c

diff --git a/mm/util.c b/mm/util.c
index 3492a9e..0837570 100644 (file)
--- a/mm/util.c
+++ b/mm/util.c
@@ -27,6 +27,7 @@
 #include <linux/uaccess.h>
 
 #include "internal.h"
+#include "swap.h"
 
 /**
  * kfree_const - conditionally free memory
@@ -343,8 +344,40 @@ unsigned long randomize_stack_top(unsigned long stack_top)
 #endif
 }
 
+/**
+ * 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.
+ *
+ * NOTE: Historical use of randomize_range, which this replaces, presumed that
+ * @start was already page aligned.  We now align it regardless.
+ *
+ * Return: A page aligned address within [start, start + range).  On error,
+ * @start is returned.
+ */
+unsigned long randomize_page(unsigned long start, unsigned long range)
+{
+       if (!PAGE_ALIGNED(start)) {
+               range -= PAGE_ALIGN(start) - start;
+               start = PAGE_ALIGN(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);
+}
+
 #ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
-unsigned long arch_randomize_brk(struct mm_struct *mm)
+unsigned long __weak arch_randomize_brk(struct mm_struct *mm)
 {
        /* Is the current task 32bit ? */
        if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task())