Index: head/bin/sh/memalloc.c
===================================================================
--- head/bin/sh/memalloc.c
+++ head/bin/sh/memalloc.c
@@ -50,6 +50,13 @@
 #include <stdlib.h>
 #include <unistd.h>
 
+static void
+badalloc(const char *message)
+{
+	write(2, message, strlen(message));
+	abort();
+}
+
 /*
  * Like malloc, but returns an error when out of space.
  */
@@ -59,9 +66,9 @@
 {
 	pointer p;
 
-	INTOFF;
+	if (!is_int_on())
+		badalloc("Unsafe ckmalloc() call\n");
 	p = malloc(nbytes);
-	INTON;
 	if (p == NULL)
 		error("Out of space");
 	return p;
@@ -75,9 +82,9 @@
 pointer
 ckrealloc(pointer p, int nbytes)
 {
-	INTOFF;
+	if (!is_int_on())
+		badalloc("Unsafe ckrealloc() call\n");
 	p = realloc(p, nbytes);
-	INTON;
 	if (p == NULL)
 		error("Out of space");
 	return p;
@@ -86,9 +93,9 @@
 void
 ckfree(pointer p)
 {
-	INTOFF;
+	if (!is_int_on())
+		badalloc("Unsafe ckfree() call\n");
 	free(p);
-	INTON;
 }