xorg-server: fix CVE-1940

http://lists.x.org/archives/xorg-devel/2013-April/036014.html
It's a low-priority issue, but it should cause almost no rebuilds.

pkgs/servers/x11/xorg/overrides.nix

@@ -221,7 +221,7 @@ in
 
   xorgserver = attrs: attrs // {
     configureFlags = "--enable-xcsecurity"; # enable SECURITY extension
-    patches = [./xorgserver-dri-path.patch ./xorgserver-xkbcomp-path.patch];
+    patches = [./xorgserver-dri-path.patch ./xorgserver-xkbcomp-path.patch ./xorgserver12-CVE-1940.patch];
     buildInputs = attrs.buildInputs ++
       [ args.zlib args.udev args.mesa args.dbus.libs
         xorg.xf86bigfontproto xorg.glproto xorg.xf86driproto

pkgs/servers/x11/xorg/xorgserver12-CVE-1940.patch

@@ -0,0 +1,34 @@
+From 6ca03b9161d33b1d2b55a3a1a913cf88deb2343f Mon Sep 17 00:00:00 2001
+From: Dave Airlie <airlied@gmail.com>
+Date: Wed, 10 Apr 2013 06:09:01 +0000
+Subject: xf86: fix flush input to work with Linux evdev devices.
+
+So when we VT switch back and attempt to flush the input devices,
+we don't succeed because evdev won't return part of an event,
+since we were only asking for 4 bytes, we'd only get -EINVAL back.
+
+This could later cause events to be flushed that we shouldn't have
+gotten.
+
+This is a fix for CVE-2013-1940.
+
+Signed-off-by: Dave Airlie <airlied@redhat.com>
+Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
+Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
+---
+diff --git a/hw/xfree86/os-support/shared/posix_tty.c b/hw/xfree86/os-support/shared/posix_tty.c
+index ab3757a..4d08c1e 100644
+--- a/hw/xfree86/os-support/shared/posix_tty.c
++++ b/hw/xfree86/os-support/shared/posix_tty.c
+@@ -421,7 +421,8 @@ xf86FlushInput(int fd)
+ {
+     fd_set fds;
+     struct timeval timeout;
+-    char c[4];
++    /* this needs to be big enough to flush an evdev event. */
++    char c[256];
+ 
+     DebugF("FlushingSerial\n");
+     if (tcflush(fd, TCIFLUSH) == 0)
+--
+cgit v0.9.0.2-2-gbebe