gnu: libxfixes: Fix CVE-2016-7944.

* gnu/packages/patches/libxfixes-CVE-2016-7944.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/xorg.scm (libxfixes)[replacement]: New field.
(libxfixes/fixed): New variable.

gnu/local.mk

@@ -671,6 +671,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/libwmf-CVE-2015-4696.patch		\
   %D%/packages/patches/libx11-CVE-2016-7942.patch		\
   %D%/packages/patches/libx11-CVE-2016-7943.patch		\
+  %D%/packages/patches/libxfixes-CVE-2016-7944.patch		\
   %D%/packages/patches/libxslt-generated-ids.patch		\
   %D%/packages/patches/lirc-localstatedir.patch			\
   %D%/packages/patches/llvm-for-extempore.patch			\

gnu/packages/patches/libxfixes-CVE-2016-7944.patch

@@ -0,0 +1,62 @@
+Fix CVE-2016-7944:
+
+https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-7944
+
+Patch copied from upstream source repository:
+
+https://cgit.freedesktop.org/xorg/lib/libXfixes/commit/?id=61c1039ee23a2d1de712843bed3480654d7ef42e
+
+From 61c1039ee23a2d1de712843bed3480654d7ef42e Mon Sep 17 00:00:00 2001
+From: Tobias Stoeckmann <tobias@stoeckmann.org>
+Date: Sun, 25 Sep 2016 22:38:44 +0200
+Subject: [PATCH] Integer overflow on illegal server response
+
+The 32 bit field "rep.length" is not checked for validity, which allows
+an integer overflow on 32 bit systems.
+
+A malicious server could send INT_MAX as length, which gets multiplied
+by the size of XRectangle. In that case the client won't read the whole
+data from server, getting out of sync.
+
+Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
+Reviewed-by: Matthieu Herrb <matthieu@herrb.eu>
+---
+ src/Region.c | 15 ++++++++++++---
+ 1 file changed, 12 insertions(+), 3 deletions(-)
+
+diff --git a/src/Region.c b/src/Region.c
+index cb0cf6e..59bcc1a 100644
+--- a/src/Region.c
++++ b/src/Region.c
+@@ -23,6 +23,7 @@
+ #ifdef HAVE_CONFIG_H
+ #include <config.h>
+ #endif
++#include <limits.h>
+ #include "Xfixesint.h"
+ 
+ XserverRegion
+@@ -333,9 +334,17 @@ XFixesFetchRegionAndBounds (Display	    *dpy,
+     bounds->y = rep.y;
+     bounds->width = rep.width;
+     bounds->height = rep.height;
+-    nbytes = (long) rep.length << 2;
+-    nrects = rep.length >> 1;
+-    rects = Xmalloc (nrects * sizeof (XRectangle));
++
++    if (rep.length < (INT_MAX >> 2)) {
++	nbytes = (long) rep.length << 2;
++	nrects = rep.length >> 1;
++	rects = Xmalloc (nrects * sizeof (XRectangle));
++    } else {
++	nbytes = 0;
++	nrects = 0;
++	rects = NULL;
++    }
++
+     if (!rects)
+     {
+ 	_XEatDataWords(dpy, rep.length);
+-- 
+2.10.1
+

gnu/packages/xorg.scm

@@ -4823,6 +4823,7 @@ an X Window System display.")
 (define-public libxfixes
   (package
     (name "libxfixes")
+    (replacement libxfixes/fixed)
     (version "5.0.1")
     (source
       (origin
@@ -4847,6 +4848,13 @@ an X Window System display.")
     (description "Library for the XFixes Extension to the X11 protocol.")
     (license license:x11)))
 
+(define libxfixes/fixed
+  (package
+    (inherit libxfixes)
+    (source (origin
+              (inherit (package-source libxfixes))
+              (patches (search-patches
+                         "libxfixes-CVE-2016-7944.patch"))))))
 
 (define-public libxfont
   (package