integer overflow in XF86DRIOpenConnection() [CVE-2013-1993 1/2]

busIdStringLength is a CARD32 and needs to be bounds checked before adding
one to it to come up with the total size to allocate, to avoid integer
overflow leading to underallocation and writing data from the network past
the end of the allocated buffer.

NOTE: This is a candidate for stable release branches.

Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

src/glx/XF86dri.c

@@ -43,6 +43,7 @@ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include <X11/extensions/Xext.h>
 #include <X11/extensions/extutil.h>
 #include "xf86dristr.h"
+#include <limits.h>
 
 static XExtensionInfo _xf86dri_info_data;
 static XExtensionInfo *xf86dri_info = &_xf86dri_info_data;
@@ -201,7 +202,11 @@ XF86DRIOpenConnection(Display * dpy, int screen, drm_handle_t * hSAREA,
    }
 
    if (rep.length) {
-      if (!(*busIdString = calloc(rep.busIdStringLength + 1, 1))) {
+      if (rep.busIdStringLength < INT_MAX)
+         *busIdString = calloc(rep.busIdStringLength + 1, 1);
+      else
+         *busIdString = NULL;
+      if (*busIdString == NULL) {
          _XEatData(dpy, ((rep.busIdStringLength + 3) & ~3));
          UnlockDisplay(dpy);
          SyncHandle();