gnu: libxrender: Fix CVE-2016-{7949,7950}.

* gnu/packages/patches/libxrender-CVE-2016-7949.patch,
gnu/packages/patches/libxrender-CVE-2016-7950.patch: New files.
* gnu/local.mk (dist_patch_DATA): Add them.
* gnu/packages/xorg.scm (libxrender)[replacement]: New field.
(libxrender/fixed): New variable.

gnu/local.mk

@@ -674,6 +674,8 @@ dist_patch_DATA =						\
   %D%/packages/patches/libxfixes-CVE-2016-7944.patch		\
   %D%/packages/patches/libxi-CVE-2016-7945-CVE-2016-7946.patch	\
   %D%/packages/patches/libxrandr-CVE-2016-7947-CVE-2016-7948.patch	\
+  %D%/packages/patches/libxrender-CVE-2016-7949.patch		\
+  %D%/packages/patches/libxrender-CVE-2016-7950.patch		\
   %D%/packages/patches/libxslt-generated-ids.patch		\
   %D%/packages/patches/lirc-localstatedir.patch			\
   %D%/packages/patches/llvm-for-extempore.patch			\

gnu/packages/patches/libxrender-CVE-2016-7949.patch

@@ -0,0 +1,66 @@
+Fix CVE-2016-7949:
+
+https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-7949
+
+Patch copied from upstream source repository:
+
+https://cgit.freedesktop.org/xorg/lib/libXrender/commit/?id=9362c7ddd1af3b168953d0737877bc52d79c94f4
+
+From 9362c7ddd1af3b168953d0737877bc52d79c94f4 Mon Sep 17 00:00:00 2001
+From: Tobias Stoeckmann <tobias@stoeckmann.org>
+Date: Sun, 25 Sep 2016 21:43:09 +0200
+Subject: [PATCH] Validate lengths while parsing server data.
+
+Individual lengths inside received server data can overflow
+the previously reserved memory.
+
+It is therefore important to validate every single length
+field to not overflow the previously agreed sum of all invidual
+length fields.
+
+v2: consume remaining bytes in the reply buffer on error.
+
+Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
+Reviewed-by: Matthieu Herrb@laas.fr
+---
+ src/Xrender.c | 18 ++++++++++++++++++
+ 1 file changed, 18 insertions(+)
+
+diff --git a/src/Xrender.c b/src/Xrender.c
+index 3102eb2..71cf3e6 100644
+--- a/src/Xrender.c
++++ b/src/Xrender.c
+@@ -533,12 +533,30 @@ XRenderQueryFormats (Display *dpy)
+ 	screen->fallback = _XRenderFindFormat (xri, xScreen->fallback);
+ 	screen->subpixel = SubPixelUnknown;
+ 	xDepth = (xPictDepth *) (xScreen + 1);
++	if (screen->ndepths > rep.numDepths) {
++	    Xfree (xri);
++	    Xfree (xData);
++	    _XEatDataWords (dpy, rep.length);
++	    UnlockDisplay (dpy);
++	    SyncHandle ();
++	    return 0;
++	}
++	rep.numDepths -= screen->ndepths;
+ 	for (nd = 0; nd < screen->ndepths; nd++)
+ 	{
+ 	    depth->depth = xDepth->depth;
+ 	    depth->nvisuals = xDepth->nPictVisuals;
+ 	    depth->visuals = visual;
+ 	    xVisual = (xPictVisual *) (xDepth + 1);
++	    if (depth->nvisuals > rep.numVisuals) {
++		Xfree (xri);
++		Xfree (xData);
++		_XEatDataWords (dpy, rep.length);
++		UnlockDisplay (dpy);
++		SyncHandle ();
++		return 0;
++	    }
++	    rep.numVisuals -= depth->nvisuals;
+ 	    for (nv = 0; nv < depth->nvisuals; nv++)
+ 	    {
+ 		visual->visual = _XRenderFindVisual (dpy, xVisual->visual);
+-- 
+2.10.1
+

gnu/packages/patches/libxrender-CVE-2016-7950.patch

@@ -0,0 +1,73 @@
+Fix CVE-2016-7950:
+
+https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-7950
+
+Patch copied from upstream source repository:
+
+https://cgit.freedesktop.org/xorg/lib/libXrender/commit/?id=8fad00b0b647ee662ce4737ca15be033b7a21714
+
+From 8fad00b0b647ee662ce4737ca15be033b7a21714 Mon Sep 17 00:00:00 2001
+From: Tobias Stoeckmann <tobias@stoeckmann.org>
+Date: Sun, 25 Sep 2016 21:42:09 +0200
+Subject: [PATCH] Avoid OOB write in XRenderQueryFilters
+
+The memory for filter names is reserved right after receiving the reply.
+After that, filters are iterated and each individual filter name is
+stored in that reserved memory.
+
+The individual name lengths are not checked for validity, which means
+that a malicious server can reserve less memory than it will write to
+during each iteration.
+
+v2: consume remaining bytes in reply buffer on error.
+
+Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
+Reviewed-by: Matthieu Herrb <matthieu@herrb.eu>
+---
+ src/Filter.c | 13 ++++++++++++-
+ 1 file changed, 12 insertions(+), 1 deletion(-)
+
+diff --git a/src/Filter.c b/src/Filter.c
+index edfa572..8d701eb 100644
+--- a/src/Filter.c
++++ b/src/Filter.c
+@@ -38,7 +38,7 @@ XRenderQueryFilters (Display *dpy, Drawable drawable)
+     char			*name;
+     char			len;
+     int				i;
+-    unsigned long		nbytes, nbytesAlias, nbytesName;
++    unsigned long		nbytes, nbytesAlias, nbytesName, reply_left;
+ 
+     if (!RenderHasExtension (info))
+ 	return NULL;
+@@ -114,6 +114,7 @@ XRenderQueryFilters (Display *dpy, Drawable drawable)
+      * Read the filter aliases
+      */
+     _XRead16Pad (dpy, filters->alias, 2 * rep.numAliases);
++    reply_left = 8 + rep.length - 2 * rep.numAliases;;
+ 
+     /*
+      * Read the filter names
+@@ -122,9 +123,19 @@ XRenderQueryFilters (Display *dpy, Drawable drawable)
+     {
+ 	int	l;
+ 	_XRead (dpy, &len, 1);
++	reply_left--;
+ 	l = len & 0xff;
++	if ((unsigned long)l + 1 > nbytesName) {
++            _XEatDataWords(dpy, reply_left);
++	    Xfree(filters);
++	    UnlockDisplay (dpy);
++	    SyncHandle ();
++	    return NULL;
++	}
++	nbytesName -= l + 1;
+ 	filters->filter[i] = name;
+ 	_XRead (dpy, name, l);
++        reply_left -= l;
+ 	name[l] = '\0';
+ 	name += l + 1;
+     }
+-- 
+2.10.1
+

gnu/packages/xorg.scm

@@ -4602,6 +4602,7 @@ cannot be adequately worked around on the client side of the wire.")
 (define-public libxrender
   (package
     (name "libxrender")
+    (replacement libxrender/fixed)
     (version "0.9.9")
     (source
       (origin
@@ -4626,6 +4627,14 @@ cannot be adequately worked around on the client side of the wire.")
     (description "Library for the Render Extension to the X11 protocol.")
     (license license:x11)))
 
+(define libxrender/fixed
+  (package
+    (inherit libxrender)
+    (source (origin
+              (inherit (package-source libxrender))
+              (patches (search-patches
+                         "libxrender-CVE-2016-7949.patch"
+                         "libxrender-CVE-2016-7950.patch"))))))
 
 (define-public libxtst
   (package