powerpc: Randomise the brk region
Randomize the heap.
before:
tundro2:~ # sleep 1 & cat /proc/${!}/maps | grep heap
10017000-10118000 rw-p 10017000 00:00 0 [heap]
10017000-10118000 rw-p 10017000 00:00 0 [heap]
10017000-10118000 rw-p 10017000 00:00 0 [heap]
10017000-10118000 rw-p 10017000 00:00 0 [heap]
10017000-10118000 rw-p 10017000 00:00 0 [heap]
after
tundro2:~ # sleep 1 & cat /proc/${!}/maps | grep heap
19419000-1951a000 rw-p 19419000 00:00 0 [heap]
325ff000-32700000 rw-p 325ff000 00:00 0 [heap]
1a97c000-1aa7d000 rw-p 1a97c000 00:00 0 [heap]
1cc60000-1cd61000 rw-p 1cc60000 00:00 0 [heap]
1afa9000-1b0aa000 rw-p 1afa9000 00:00 0 [heap]
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 69b9d2d..30b149c 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1147,3 +1147,26 @@
sp -= get_random_int() & ~PAGE_MASK;
return sp & ~0xf;
}
+
+static inline unsigned long brk_rnd(void)
+{
+ unsigned long rnd = 0;
+
+ /* 8MB for 32bit, 1GB for 64bit */
+ if (is_32bit_task())
+ rnd = (long)(get_random_int() % (1<<(23-PAGE_SHIFT)));
+ else
+ rnd = (long)(get_random_int() % (1<<(30-PAGE_SHIFT)));
+
+ return rnd << PAGE_SHIFT;
+}
+
+unsigned long arch_randomize_brk(struct mm_struct *mm)
+{
+ unsigned long ret = PAGE_ALIGN(mm->brk + brk_rnd());
+
+ if (ret < mm->brk)
+ return mm->brk;
+
+ return ret;
+}
