Bug 285991 (CVE-2007-4730)

Summary:	CVE-2007-4730 X.org composite extension buffer overflow
Product:	[Other] Security Response	Reporter:	Josh Bressers <bressers>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	kreilly, xgl-maint
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
URL:	http://bugs.freedesktop.org/show_bug.cgi?id=7447
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2007-10-26 09:16:28 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	286051, 286061, 286071, 286081, 286091, 286101, 286111
Bug Blocks:

Description Josh Bressers 2007-09-11 14:01:10 UTC

A buffer overflow flaw has been found in the X.org composite extension.  The
upstream bug has more details:

http://bugs.freedesktop.org/show_bug.cgi?id=7447

By running a server at depth 16, it becomes possible for a local user to
overflow a buffer by creating a window with depth 32, then resizing it.

Comment 2 Søren Sandmann Pedersen 2007-09-11 19:15:15 UTC

FC6, F7, Fdevel, and rhels 5.0.z, 5.1 are not vulnerable because of this patch:

localhost:~/vertigo/rpms/xorg-x11-server/RHEL-5% cat
xorg-x11-server-1.1.0-dont-backfill-bg-none.patch
Disable backfilling of windows created with bg=none, which otherwise
would force a framebuffer readback.

--- ./composite/compalloc.c.spiffiffity 2006-03-13 16:59:55.000000000 -0500
+++ ./composite/compalloc.c     2006-04-12 16:37:50.000000000 -0400
@@ -478,6 +478,7 @@
      * Copy bits from the parent into the new pixmap so that it will
      * have "reasonable" contents in case for background None areas.
      */
+#if 0
     if (pGC)
     {
        XID val = IncludeInferiors;
@@ -492,6 +493,7 @@
                               w, h, 0, 0);
        FreeScratchGC (pGC);
     }
+#endif
     return pPixmap;
 }

Comment 3 Josh Bressers 2007-09-18 11:55:22 UTC

We are changing the severity here to moderate. Here is some additional
information provided by Adam Jackson:

- the Composite extension is not enabled by default in RHEL4, so the user
  would have had to go out of their way to turn it on.
- we don't ship any compositing manager in RHEL4, so they'd need to have
  installed one.
- the exploit requires the ability to authenticate to the X server, so the
  attacker would need to have already gained rights equivalent to the user.

Comment 4 Tomas Hoger 2007-10-26 09:16:28 UTC

For Red Hat Enterprise Linux 4, this issue was addressed in RHSA-2007:0898:

https://rhn.redhat.com/errata/RHSA-2007-0898.html

Red Hat Enterprise Linux 5 and current versions of Fedora were not affected as
described in comment #2.