Xephyr: integer overflow in XF86DRIOpenConnection()

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.

Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Julien Cristau <jcristau@debian.org>

diff --git a/hw/kdrive/ephyr/XF86dri.c b/hw/kdrive/ephyr/XF86dri.c
index 9d742f3..7074bc3 100644 (file)
--- a/hw/kdrive/ephyr/XF86dri.c
+++ b/hw/kdrive/ephyr/XF86dri.c
@@ -64,6 +64,7 @@ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include <GL/glx.h>
 #include "xf86dri.h"
 #include <X11/dri/xf86driproto.h>
+#include <limits.h>
 
 static XExtensionInfo _xf86dri_info_data;
 static XExtensionInfo *xf86dri_info = &_xf86dri_info_data;
@@ -225,7 +226,11 @@ XF86DRIOpenConnection(Display * dpy, int screen,
     }
 
     if (rep.length) {
-        if (!(*busIdString = (char *) 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();