gnu: libx11: Fix CVE-2016-{7942,7943}.

* gnu/packages/patches/libx11-CVE-2016-7942.patch,
gnu/packages/patches/libx11-CVE-2016-7943.patch: New files.
* gnu/local.mk (dist_patch_DATA): Add them.
* gnu/packages/xorg.scm (libx11)[replacement]: New field.
(libx11/fixed): New variable.

gnu/local.mk

@@ -669,6 +669,8 @@ dist_patch_DATA =						\
   %D%/packages/patches/libwmf-CVE-2015-0848+CVE-2015-4588.patch	\
   %D%/packages/patches/libwmf-CVE-2015-4695.patch		\
   %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/libxslt-generated-ids.patch		\
   %D%/packages/patches/lirc-localstatedir.patch			\
   %D%/packages/patches/llvm-for-extempore.patch			\

gnu/packages/patches/libx11-CVE-2016-7942.patch

@@ -0,0 +1,76 @@
+Fix CVE-2016-7942:
+
+https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-7942
+
+Patch copied from upstream source repository:
+
+https://cgit.freedesktop.org/xorg/lib/libX11/commit/?id=8ea762f94f4c942d898fdeb590a1630c83235c17
+
+From 8ea762f94f4c942d898fdeb590a1630c83235c17 Mon Sep 17 00:00:00 2001
+From: Tobias Stoeckmann <tobias@stoeckmann.org>
+Date: Sun, 25 Sep 2016 21:25:25 +0200
+Subject: [PATCH] Validation of server responses in XGetImage()
+
+Check if enough bytes were received for specified image type and
+geometry. Otherwise GetPixel and other functions could trigger an
+out of boundary read later on.
+
+Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
+Reviewed-by: Matthieu Herrb <matthieu@herrb.eu>
+---
+ src/GetImage.c | 29 ++++++++++++++++++++---------
+ 1 file changed, 20 insertions(+), 9 deletions(-)
+
+diff --git a/src/GetImage.c b/src/GetImage.c
+index c461abc..ff32d58 100644
+--- a/src/GetImage.c
++++ b/src/GetImage.c
+@@ -59,6 +59,7 @@ XImage *XGetImage (
+ 	char *data;
+ 	unsigned long nbytes;
+ 	XImage *image;
++	int planes;
+ 	LockDisplay(dpy);
+ 	GetReq (GetImage, req);
+ 	/*
+@@ -91,18 +92,28 @@ XImage *XGetImage (
+ 	    return (XImage *) NULL;
+ 	}
+         _XReadPad (dpy, data, nbytes);
+-        if (format == XYPixmap)
+-	   image = XCreateImage(dpy, _XVIDtoVisual(dpy, rep.visual),
+-		  Ones (plane_mask &
+-			(((unsigned long)0xFFFFFFFF) >> (32 - rep.depth))),
+-		  format, 0, data, width, height, dpy->bitmap_pad, 0);
+-	else /* format == ZPixmap */
+-           image = XCreateImage (dpy, _XVIDtoVisual(dpy, rep.visual),
+-		 rep.depth, ZPixmap, 0, data, width, height,
+-		  _XGetScanlinePad(dpy, (int) rep.depth), 0);
++        if (format == XYPixmap) {
++	    image = XCreateImage(dpy, _XVIDtoVisual(dpy, rep.visual),
++		Ones (plane_mask &
++		    (((unsigned long)0xFFFFFFFF) >> (32 - rep.depth))),
++		format, 0, data, width, height, dpy->bitmap_pad, 0);
++	    planes = image->depth;
++	} else { /* format == ZPixmap */
++            image = XCreateImage (dpy, _XVIDtoVisual(dpy, rep.visual),
++		rep.depth, ZPixmap, 0, data, width, height,
++		    _XGetScanlinePad(dpy, (int) rep.depth), 0);
++	    planes = 1;
++	}
+ 
+ 	if (!image)
+ 	    Xfree(data);
++	if (planes < 1 || image->height < 1 || image->bytes_per_line < 1 ||
++	    INT_MAX / image->height <= image->bytes_per_line ||
++	    INT_MAX / planes <= image->height * image->bytes_per_line ||
++	    nbytes < planes * image->height * image->bytes_per_line) {
++	    XDestroyImage(image);
++	    image = NULL;
++	}
+ 	UnlockDisplay(dpy);
+ 	SyncHandle();
+ 	return (image);
+-- 
+2.10.1
+

gnu/packages/patches/libx11-CVE-2016-7943.patch

@@ -0,0 +1,113 @@
+Fix CVE-2016-7943:
+
+https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-7943.
+
+Patch copied from upstream source repository:
+
+https://cgit.freedesktop.org/xorg/lib/libX11/commit/?id=8c29f1607a31dac0911e45a0dd3d74173822b3c9
+
+From 8c29f1607a31dac0911e45a0dd3d74173822b3c9 Mon Sep 17 00:00:00 2001
+From: Tobias Stoeckmann <tobias@stoeckmann.org>
+Date: Sun, 25 Sep 2016 21:22:57 +0200
+Subject: [PATCH] The validation of server responses avoids out of boundary
+ accesses.
+
+v2: FontNames.c  return a NULL list whenever a single
+length field from the server is incohent.
+
+Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
+Reviewed-by: Matthieu Herrb <matthieu@herrb.eu>
+---
+ src/FontNames.c | 23 +++++++++++++++++------
+ src/ListExt.c   | 12 ++++++++----
+ src/ModMap.c    |  3 ++-
+ 3 files changed, 27 insertions(+), 11 deletions(-)
+
+diff --git a/src/FontNames.c b/src/FontNames.c
+index 21dcafe..e55f338 100644
+--- a/src/FontNames.c
++++ b/src/FontNames.c
+@@ -66,7 +66,7 @@ int *actualCount)	/* RETURN */
+ 
+     if (rep.nFonts) {
+ 	flist = Xmalloc (rep.nFonts * sizeof(char *));
+-	if (rep.length < (INT_MAX >> 2)) {
++	if (rep.length > 0 && rep.length < (INT_MAX >> 2)) {
+ 	    rlen = rep.length << 2;
+ 	    ch = Xmalloc(rlen + 1);
+ 	    /* +1 to leave room for last null-terminator */
+@@ -93,11 +93,22 @@ int *actualCount)	/* RETURN */
+ 	    if (ch + length < chend) {
+ 		flist[i] = ch + 1;  /* skip over length */
+ 		ch += length + 1;  /* find next length ... */
+-		length = *(unsigned char *)ch;
+-		*ch = '\0';  /* and replace with null-termination */
+-		count++;
+-	    } else
+-		flist[i] = NULL;
++		if (ch <= chend) {
++		    length = *(unsigned char *)ch;
++		    *ch = '\0';  /* and replace with null-termination */
++		    count++;
++		} else {
++                    Xfree(flist);
++                    flist = NULL;
++                    count = 0;
++                    break;
++		}
++	    } else {
++                Xfree(flist);
++                flist = NULL;
++                count = 0;
++                break;
++            }
+ 	}
+     }
+     *actualCount = count;
+diff --git a/src/ListExt.c b/src/ListExt.c
+index be6b989..0516e45 100644
+--- a/src/ListExt.c
++++ b/src/ListExt.c
+@@ -55,7 +55,7 @@ char **XListExtensions(
+ 
+ 	if (rep.nExtensions) {
+ 	    list = Xmalloc (rep.nExtensions * sizeof (char *));
+-	    if (rep.length < (INT_MAX >> 2)) {
++	    if (rep.length > 0 && rep.length < (INT_MAX >> 2)) {
+ 		rlen = rep.length << 2;
+ 		ch = Xmalloc (rlen + 1);
+                 /* +1 to leave room for last null-terminator */
+@@ -80,9 +80,13 @@ char **XListExtensions(
+ 		if (ch + length < chend) {
+ 		    list[i] = ch+1;  /* skip over length */
+ 		    ch += length + 1; /* find next length ... */
+-		    length = *ch;
+-		    *ch = '\0'; /* and replace with null-termination */
+-		    count++;
++		    if (ch <= chend) {
++			length = *ch;
++			*ch = '\0'; /* and replace with null-termination */
++			count++;
++		    } else {
++			list[i] = NULL;
++		    }
+ 		} else
+ 		    list[i] = NULL;
+ 	    }
+diff --git a/src/ModMap.c b/src/ModMap.c
+index a809aa2..49a5d08 100644
+--- a/src/ModMap.c
++++ b/src/ModMap.c
+@@ -42,7 +42,8 @@ XGetModifierMapping(register Display *dpy)
+     GetEmptyReq(GetModifierMapping, req);
+     (void) _XReply (dpy, (xReply *)&rep, 0, xFalse);
+ 
+-    if (rep.length < (INT_MAX >> 2)) {
++    if (rep.length < (INT_MAX >> 2) &&
++	(rep.length >> 1) == rep.numKeyPerModifier) {
+ 	nbytes = (unsigned long)rep.length << 2;
+ 	res = Xmalloc(sizeof (XModifierKeymap));
+ 	if (res)
+-- 
+2.10.1
+

gnu/packages/xorg.scm

@@ -5181,6 +5181,7 @@ (define-public xorg-server-xwayland
 (define-public libx11
   (package
     (name "libx11")
+    (replacement libx11/fixed)
     (version "1.6.3")
     (source
       (origin
@@ -5213,6 +5214,14 @@ (define-public libx11
     (description "Xorg Core X11 protocol client library.")
     (license license:x11)))
 
+(define libx11/fixed
+  (package
+    (inherit libx11)
+    (source (origin
+              (inherit (package-source libx11))
+              (patches (search-patches
+                         "libx11-CVE-2016-7942.patch"
+                         "libx11-CVE-2016-7943.patch"))))))
 
 ;; packages of height 5 in the propagated-inputs tree