Use _XEatDataWords to avoid overflow of rep.length shifting

rep.length is a CARD32, so rep.length << 2 could overflow in 32-bit builds

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>

2 files changed, 20 insertions, 2 deletions

diff --git a/configure.ac b/configure.ac
index 90205cc..f68b689 100644
--- a/configure.ac
+++ b/configure.ac
@@ -50,6 +50,12 @@ XORG_CHECK_MALLOC_ZERO
 # Obtain compiler/linker options for depedencies
 PKG_CHECK_MODULES(XRES, x11 xext xextproto [resourceproto >= 1.2.0])
 
+# Check for _XEatDataWords function that may be patched into older Xlib release
+SAVE_LIBS="$LIBS"
+LIBS="$XRES_LIBS"
+AC_CHECK_FUNCS([_XEatDataWords])
+LIBS="$SAVE_LIBS"
+
 AC_CONFIG_FILES([Makefile
 		src/Makefile
 		man/Makefile
diff --git a/src/XRes.c b/src/XRes.c
index 1744196..1ab1db8 100644
--- a/src/XRes.c
+++ b/src/XRes.c
@@ -13,6 +13,18 @@
 #include <X11/extensions/XResproto.h>
 #include <X11/extensions/XRes.h>
 #include <assert.h>
+#include <limits.h>
+
+#ifndef HAVE__XEATDATAWORDS
+static inline void _XEatDataWords(Display *dpy, unsigned long n)
+{
+# ifndef LONG64
+    if (n >= (ULONG_MAX >> 2))
+        _XIOError(dpy);
+# endif
+    _XEatData (dpy, n << 2);
+}
+#endif
 
 static XExtensionInfo _xres_ext_info_data;
 static XExtensionInfo *xres_ext_info = &_xres_ext_info_data;
@@ -131,7 +143,7 @@ Status XResQueryClients (
             *num_clients = rep.num_clients;
             result = 1;
         } else {
-            _XEatData(dpy, rep.length << 2);
+            _XEatDataWords(dpy, rep.length);
         }
     }
 
@@ -183,7 +195,7 @@ Status XResQueryClientResources (
             *num_types = rep.num_types;
             result = 1;
         } else {
-            _XEatData(dpy, rep.length << 2);
+            _XEatDataWords(dpy, rep.length);
         }
     }