Fix CVE-2013-4396.

From a4d9bf1259ad28f54b6d59a480b2009cc89ca623 Mon Sep 17 00:00:00 2001
From: Alan Coopersmith <alan.coopersmith@oracle.com>
Date: Mon, 16 Sep 2013 21:47:16 -0700
Subject: [PATCH] Avoid use-after-free in dix/dixfonts.c: doImageText()

Save a pointer to the passed in closure structure before copying it
and overwriting the *c pointer to point to our copy instead of the
original.  If we hit an error, once we free(c), reset c to point to
the original structure before jumping to the cleanup code that
references *c.

Since one of the errors being checked for is whether the server was
able to malloc(c->nChars * itemSize), the client can potentially pass
a number of characters chosen to cause the malloc to fail and the
error path to be taken, resulting in the read from freed memory.

Since the memory is accessed almost immediately afterwards, and the
X server is mostly single threaded, the odds of the free memory having
invalid contents are low with most malloc implementations when not using
memory debugging features, but some allocators will definitely overwrite
the memory there, leading to a likely crash.

Reported-by: Pedro Ribeiro <pedrib@gmail.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Julien Cristau <jcristau@debian.org>


Bump PKGREVISION.

3 files changed, 78 insertions, 4 deletions

diff --git a/x11/modular-xorg-server/Makefile b/x11/modular-xorg-server/Makefile
index d55fa3ef4f0..5838bab60cc 100644
--- a/x11/modular-xorg-server/Makefile
+++ b/x11/modular-xorg-server/Makefile
@@ -1,9 +1,8 @@
-# $NetBSD: Makefile,v 1.80 2013/06/16 13:34:30 obache Exp $
-#
+# $NetBSD: Makefile,v 1.81 2013/10/08 20:33:54 wiz Exp $
 
 DISTNAME=	xorg-server-1.12.4
 PKGNAME=	modular-${DISTNAME}
-PKGREVISION=	2
+PKGREVISION=	3
 CATEGORIES=	x11
 MASTER_SITES=	${MASTER_SITE_XORG:=xserver/}
 EXTRACT_SUFX=	.tar.bz2
diff --git a/x11/modular-xorg-server/distinfo b/x11/modular-xorg-server/distinfo
index 63df5061ef5..dc4e5d6ad73 100644
--- a/x11/modular-xorg-server/distinfo
+++ b/x11/modular-xorg-server/distinfo
@@ -1,8 +1,9 @@
-$NetBSD: distinfo,v 1.51 2013/05/21 18:38:03 joerg Exp $
+$NetBSD: distinfo,v 1.52 2013/10/08 20:33:54 wiz Exp $
 
 SHA1 (xorg-server-1.12.4.tar.bz2) = 6d616874f9c7677bda08dc073c03f83e78fbc585
 RMD160 (xorg-server-1.12.4.tar.bz2) = 4907b5dc42efd6b3fb6bf9d64f1441080a6a6983
 Size (xorg-server-1.12.4.tar.bz2) = 5444761 bytes
 SHA1 (patch-configure) = 031bc0accf1dd71ed687e7aac3fcc9498cb06784
+SHA1 (patch-dix_dixfonts.c) = 2f1fd51c538eab12c06b85c4ddab18af25338174
 SHA1 (patch-hw_xfree86_common_compiler.h) = 88de747715b80b22f448869ab32dce1641bcb6db
 SHA1 (patch-hw_xfree86_os-support_xf86__OSlib.h) = 7c2760509610b44915da077b22899bef9c338cc1
diff --git a/x11/modular-xorg-server/patches/patch-dix_dixfonts.c b/x11/modular-xorg-server/patches/patch-dix_dixfonts.c
new file mode 100644
index 00000000000..33e9d541ae5
--- /dev/null
+++ b/x11/modular-xorg-server/patches/patch-dix_dixfonts.c
@@ -0,0 +1,74 @@
+$NetBSD: patch-dix_dixfonts.c,v 1.1 2013/10/08 20:33:54 wiz Exp $
+
+Fix CVE-2013-4396.
+
+From a4d9bf1259ad28f54b6d59a480b2009cc89ca623 Mon Sep 17 00:00:00 2001
+From: Alan Coopersmith <alan.coopersmith@oracle.com>
+Date: Mon, 16 Sep 2013 21:47:16 -0700
+Subject: [PATCH] Avoid use-after-free in dix/dixfonts.c: doImageText()
+
+Save a pointer to the passed in closure structure before copying it
+and overwriting the *c pointer to point to our copy instead of the
+original.  If we hit an error, once we free(c), reset c to point to
+the original structure before jumping to the cleanup code that
+references *c.
+
+Since one of the errors being checked for is whether the server was
+able to malloc(c->nChars * itemSize), the client can potentially pass
+a number of characters chosen to cause the malloc to fail and the
+error path to be taken, resulting in the read from freed memory.
+
+Since the memory is accessed almost immediately afterwards, and the
+X server is mostly single threaded, the odds of the free memory having
+invalid contents are low with most malloc implementations when not using
+memory debugging features, but some allocators will definitely overwrite
+the memory there, leading to a likely crash.
+
+Reported-by: Pedro Ribeiro <pedrib@gmail.com>
+Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
+Reviewed-by: Julien Cristau <jcristau@debian.org>
+---
+ dix/dixfonts.c |    5 +++++
+ 1 file changed, 5 insertions(+)
+
+--- dix/dixfonts.c.orig	2012-05-17 17:09:01.000000000 +0000
++++ dix/dixfonts.c
+@@ -1414,6 +1414,7 @@ doImageText(ClientPtr client, ITclosureP
+             GC *pGC;
+             unsigned char *data;
+             ITclosurePtr new_closure;
++            ITclosurePtr old_closure;
+ 
+             /* We're putting the client to sleep.  We need to
+                save some state.  Similar problem to that handled
+@@ -1425,12 +1426,14 @@ doImageText(ClientPtr client, ITclosureP
+                 err = BadAlloc;
+                 goto bail;
+             }
++            old_closure = c;
+             *new_closure = *c;
+             c = new_closure;
+ 
+             data = malloc(c->nChars * itemSize);
+             if (!data) {
+                 free(c);
++                c = old_closure;
+                 err = BadAlloc;
+                 goto bail;
+             }
+@@ -1441,6 +1444,7 @@ doImageText(ClientPtr client, ITclosureP
+             if (!pGC) {
+                 free(c->data);
+                 free(c);
++                c = old_closure;
+                 err = BadAlloc;
+                 goto bail;
+             }
+@@ -1453,6 +1457,7 @@ doImageText(ClientPtr client, ITclosureP
+                 FreeScratchGC(pGC);
+                 free(c->data);
+                 free(c);
++                c = old_closure;
+                 err = BadAlloc;
+                 goto bail;
+             }