1 files changed, 14 insertions, 7 deletions

diff --git a/xorg-server/hw/xwin/winmultiwindowclass.c b/xorg-server/hw/xwin/winmultiwindowclass.c
index cc7628d5c..96f69727f 100644
--- a/xorg-server/hw/xwin/winmultiwindowclass.c
+++ b/xorg-server/hw/xwin/winmultiwindowclass.c
@@ -68,7 +68,7 @@ winMultiWindowGetClassHint(WindowPtr pWin, char **res_name, char **res_class)
     while (prop) {
         if (prop->propertyName == XA_WM_CLASS
             && prop->type == XA_STRING && prop->format == 8 && prop->data) {
-            len_name = strlen((char *) prop->data);
+            len_name = strnlen((char *) prop->data, prop->size);
 
             (*res_name) = malloc(len_name + 1);
 
@@ -78,12 +78,18 @@ winMultiWindowGetClassHint(WindowPtr pWin, char **res_name, char **res_class)
             }
 
             /* Add one to len_name to allow copying of trailing 0 */
-            strncpy((*res_name), prop->data, len_name + 1);
+            memcpy((*res_name), prop->data, len_name );
+            (*res_name)[len_name]='\0';
 
-            if (len_name == prop->size)
-                len_name--;
-
-            len_class = strlen(((char *) prop->data) + 1 + len_name);
+            if (len_name < prop->size-1)
+            {
+              // It could be that the string is not null terminated
+              len_class = strnlen(((char *) prop->data) + 1 + len_name, prop->size-1-len_name);
+            }
+            else
+            {
+              len_class = 0;
+            }
 
             (*res_class) = malloc(len_class + 1);
 
@@ -95,7 +101,8 @@ winMultiWindowGetClassHint(WindowPtr pWin, char **res_name, char **res_class)
                 return 0;
             }
 
-            strcpy((*res_class), ((char *) prop->data) + 1 + len_name);
+            memcpy((*res_class), ((char *) prop->data) + 1 + len_name, len_class);
+            (*res_class)[len_class]='\0';
 
             return 1;
         }