lib: list_sort_test(): add extra corruption check

Add a check to make sure that the prev pointer of the list head points
to the last element on the list.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Cc: Don Mullis <don.mullis@gmail.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/list_sort.c

@@ -272,6 +272,11 @@ static int __init list_sort_test(void)
 		}
 		count++;
 	}
+	if (head.prev != cur) {
+		printk(KERN_ERR "list_sort_test: error: list is corrupted\n");
+		goto exit;
+	}
+
 
 	if (count != TEST_LIST_LEN) {
 		printk(KERN_ERR "list_sort_test: error: bad list length %d",