printf() arguments shouldn't be passed straight from user supplied data.
(Security thingy.)
diff --git a/coreutils/ln.c b/coreutils/ln.c
index 6751e90..dcb70d4 100644
--- a/coreutils/ln.c
+++ b/coreutils/ln.c
@@ -106,7 +106,7 @@
 		}
 
 		if (link_func(*argv, src) != 0) {
-			bb_perror_msg(src);
+			bb_perror_msg("%s", src);
 			status = EXIT_FAILURE;
 		}