[ARM] add address randomization to mmap()

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
index f5abc51c5a07..4f5b39687df5 100644
--- a/arch/arm/mm/mmap.c
+++ b/arch/arm/mm/mmap.c
@@ -7,6 +7,7 @@
 #include <linux/shm.h>
 #include <linux/sched.h>
 #include <linux/io.h>
+#include <linux/random.h>
 #include <asm/cputype.h>
 #include <asm/system.h>
 
@@ -80,6 +81,9 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
                 start_addr = addr = TASK_UNMAPPED_BASE;
                 mm->cached_hole_size = 0;
         }
+        /* 8 bits of randomness in 20 address space bits */
+        if (current->flags & PF_RANDOMIZE)
+                addr += (get_random_int() % (1 << 8)) << PAGE_SHIFT;
 
 full_search:
         if (do_align)