1 files changed, 31 insertions, 18 deletions

diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index 869efbaed3ea..c9a9f7f18188 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -27,17 +27,44 @@
 #include <linux/personality.h>
 #include <linux/mm.h>
 #include <linux/module.h>
+#include <linux/random.h>
 #include <asm/pgalloc.h>
 #include <asm/compat.h>
 
+static unsigned long stack_maxrandom_size(void)
+{
+        if (!(current->flags & PF_RANDOMIZE))
+                return 0;
+        if (current->personality & ADDR_NO_RANDOMIZE)
+                return 0;
+        return STACK_RND_MASK << PAGE_SHIFT;
+}
+
 /*
  * Top of mmap area (just below the process stack).
  *
- * Leave an at least ~128 MB hole.
+ * Leave at least a ~32 MB hole.
  */
-#define MIN_GAP (128*1024*1024)
+#define MIN_GAP (32*1024*1024)
 #define MAX_GAP (STACK_TOP/6*5)
 
+static inline int mmap_is_legacy(void)
+{
+        if (current->personality & ADDR_COMPAT_LAYOUT)
+                return 1;
+        if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
+                return 1;
+        return sysctl_legacy_va_layout;
+}
+
+static unsigned long mmap_rnd(void)
+{
+        if (!(current->flags & PF_RANDOMIZE))
+                return 0;
+        /* 8MB randomization for mmap_base */
+        return (get_random_int() & 0x7ffUL) << PAGE_SHIFT;
+}
+
 static inline unsigned long mmap_base(void)
 {
         unsigned long gap = rlimit(RLIMIT_STACK);
@@ -46,22 +73,8 @@ static inline unsigned long mmap_base(void)
                 gap = MIN_GAP;
         else if (gap > MAX_GAP)
                 gap = MAX_GAP;
-
-        return STACK_TOP - (gap & PAGE_MASK);
-}
-
-static inline int mmap_is_legacy(void)
-{
-#ifdef CONFIG_64BIT
-        /*
-         * Force standard allocation for 64 bit programs.
-         */
-        if (!is_compat_task())
-                return 1;
-#endif
-        return sysctl_legacy_va_layout ||
-            (current->personality & ADDR_COMPAT_LAYOUT) ||
-            rlimit(RLIMIT_STACK) == RLIM_INFINITY;
+        gap &= PAGE_MASK;
+        return STACK_TOP - stack_maxrandom_size() - mmap_rnd() - gap;
 }
 
 #ifndef CONFIG_64BIT