diff -r 87f248de5230 tools/libxc/xc_tbuf.c
--- a/tools/libxc/xc_tbuf.c	Mon Nov 15 09:31:38 2010 +0000
+++ b/tools/libxc/xc_tbuf.c	Tue Nov 16 10:11:39 2010 +0100
@@ -121,6 +121,7 @@
     uint64_t mask64 = mask;
 
     bytemap = xc_hypercall_buffer_alloc(xch, bytemap, sizeof(mask64));
+    if (bytemap == NULL)
     {
         PERROR("Could not allocate memory for xc_tbuf_set_cpu_mask hypercall");
         goto out;