[PATCH 4/5] Xephyr: integer overflow in XF86DRIOpenConnection()

[Alan Coopersmith]

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 at ioactive.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith at oracle.com>
---
 hw/kdrive/ephyr/XF86dri.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/hw/kdrive/ephyr/XF86dri.c b/hw/kdrive/ephyr/XF86dri.c
index 9d742f3..b1f070e 100644
--- a/hw/kdrive/ephyr/XF86dri.c
+++ b/hw/kdrive/ephyr/XF86dri.c
@@ -225,7 +225,11 @@ 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();
-- 
1.7.9.2