From 23fe7718bb171e71db2d1a30505c2ca2988799d9 Mon Sep 17 00:00:00 2001
From: Adam Jackson <ajax@redhat.com>
Date: Mon, 10 Nov 2014 12:13:36 -0500
Subject: [PATCH 19/40] glx: Be more paranoid about variable-length requests
 [CVE-2014-8093 1/6]

If the size computation routine returns -1 we should just reject the
request outright.  Clamping it to zero could give an attacker the
opportunity to also mangle cmdlen in such a way that the subsequent
length check passes, and the request would get executed, thus passing
data we wanted to reject to the renderer.

Reviewed-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Julien Cristau <jcristau@debian.org>
Reviewed-by: Michal Srb <msrb@suse.com>
Reviewed-by: Andy Ritger <aritger@nvidia.com>
Signed-off-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
---
 glx/glxcmds.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/glx/glxcmds.c b/glx/glxcmds.c
index 009fd9b..ea42e2a 100644
--- glx/glxcmds.c
+++ glx/glxcmds.c
@@ -2062,7 +2062,7 @@ __glXDisp_Render(__GLXclientState * cl, GLbyte * pc)
             extra = (*entry.varsize) (pc + __GLX_RENDER_HDR_SIZE,
                                       client->swapped);
             if (extra < 0) {
-                extra = 0;
+                return BadLength;
             }
             if (cmdlen != __GLX_PAD(entry.bytes + extra)) {
                 return BadLength;
@@ -2179,7 +2179,7 @@ __glXDisp_RenderLarge(__GLXclientState * cl, GLbyte * pc)
             extra = (*entry.varsize) (pc + __GLX_RENDER_LARGE_HDR_SIZE,
                                       client->swapped);
             if (extra < 0) {
-                extra = 0;
+                return BadLength;
             }
             /* large command's header is 4 bytes longer, so add 4 */
             if (cmdlen != __GLX_PAD(entry.bytes + 4 + extra)) {
-- 
2.1.2

