powerpc,mmap: properly account for stack randomization in mmap_base

[karo-tx-linux.git] / arch / powerpc / mm / mmap.c

diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c
index 0ee6be4f1ba44e231da18c7e38d217610ac4bcd5..5d78b193fec4142ecd3d4d5788dfe686cf2e8e6c 100644 (file)
--- a/arch/powerpc/mm/mmap.c
+++ b/arch/powerpc/mm/mmap.c
@@ -34,16 +34,9 @@
 /*
  * Top of mmap area (just below the process stack).
  *
- * Leave at least a ~128 MB hole on 32bit applications.
- *
- * On 64bit applications we randomise the stack by 1GB so we need to
- * space our mmap start address by a further 1GB, otherwise there is a
- * chance the mmap area will end up closer to the stack than our ulimit
- * requires.
+ * Leave at least a ~128 MB hole.
  */
-#define MIN_GAP32 (128*1024*1024)
-#define MIN_GAP64 ((128 + 1024)*1024*1024UL)
-#define MIN_GAP ((is_32bit_task()) ? MIN_GAP32 : MIN_GAP64)
+#define MIN_GAP (128*1024*1024)
 #define MAX_GAP (TASK_SIZE/6*5)
 
 static inline int mmap_is_legacy(void)
@@ -71,9 +64,26 @@ unsigned long arch_mmap_rnd(void)
        return rnd << PAGE_SHIFT;
 }
 
+static inline unsigned long stack_maxrandom_size(void)
+{
+       if (!(current->flags & PF_RANDOMIZE))
+               return 0;
+
+       /* 8MB for 32bit, 1GB for 64bit */
+       if (is_32bit_task())
+               return (1<<23);
+       else
+               return (1<<30);
+}
+
 static inline unsigned long mmap_base(unsigned long rnd)
 {
        unsigned long gap = rlimit(RLIMIT_STACK);
+       unsigned long pad = stack_maxrandom_size() + stack_guard_gap;
+
+       /* Values close to RLIM_INFINITY can overflow. */
+       if (gap + pad > gap)
+               gap += pad;
 
        if (gap < MIN_GAP)
                gap = MIN_GAP;