[S390] Randomize mmap start address
Randomize mmap start address with 8MB.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index 74d663f..c9a9f7f 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -27,6 +27,7 @@
#include <linux/personality.h>
#include <linux/mm.h>
#include <linux/module.h>
+#include <linux/random.h>
#include <asm/pgalloc.h>
#include <asm/compat.h>
@@ -56,6 +57,14 @@
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);
@@ -64,8 +73,8 @@
gap = MIN_GAP;
else if (gap > MAX_GAP)
gap = MAX_GAP;
-
- return STACK_TOP - stack_maxrandom_size() - (gap & PAGE_MASK);
+ gap &= PAGE_MASK;
+ return STACK_TOP - stack_maxrandom_size() - mmap_rnd() - gap;
}
#ifndef CONFIG_64BIT