ion: Fix two small issues in system_heap allocation

In testing ion system heap allocations, I ran across two issues:

1) Not k*z*allocing the sg table. This can cause trouble if
we end up trying call sg_alloc_table() with too many entries,
then sg_alloc_table() internally fails and tries to free what it
thinks is internal table structure, which causes bad pointer
traversals.

2) The second list_for_each_entry probably should be _safe,
since I was seeing  strange lock warnings and oopses on occasion.
This seems to resolve it, but could use some extra checking.

Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/ion/ion_system_heap.c

@@ -166,8 +166,7 @@ static int ion_system_heap_allocate(struct ion_heap *heap,
 		max_order = info->order;
 		i++;
 	}
-
-	table = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
+	table = kzalloc(sizeof(struct sg_table), GFP_KERNEL);
 	if (!table)
 		goto err;
 
@@ -189,7 +188,7 @@ static int ion_system_heap_allocate(struct ion_heap *heap,
 err1:
 	kfree(table);
 err:
-	list_for_each_entry(info, &pages, list) {
+	list_for_each_entry_safe(info, tmp_info, &pages, list) {
 		free_buffer_page(sys_heap, buffer, info->page, info->order);
 		kfree(info);
 	}