[PATCH] xen: Fix xenctl_cpumap_to_cpumask buffer size check

[Matthew Daley <mattjd@gmail.com>]

xenctl_cpumap_to_cpumask incorrectly uses sizeof when checking whether
bits should be masked off from the input cpumap bitmap or not.

Fix by using the correct cpumask buffer size in place of sizeof.

Signed-off-by: Matthew Daley <mattjd@gmail.com>

diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index e153cb4..204e951 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -78,7 +78,7 @@ int xenctl_cpumap_to_cpumask(
     {
         if ( copy_from_guest(bytemap, xenctl_cpumap->bitmap, copy_bytes) )
             err = -EFAULT;
-        if ( (xenctl_cpumap->nr_cpus & 7) && (guest_bytes <= sizeof(bytemap)) )
+        if ( (xenctl_cpumap->nr_cpus & 7) && (guest_bytes <= (nr_cpu_ids + 7) / 8) )
             bytemap[guest_bytes-1] &= ~(0xff << (xenctl_cpumap->nr_cpus & 7));
     }
 
-- 
1.7.10.4