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Category:   OS (UNIX)  >   NetBSD Vendors:   NetBSD
NetBSD Display Driver Bug Lets Local Users Deny Service
SecurityTracker Alert ID:  1018693
SecurityTracker URL:
CVE Reference:   CVE-2007-3654   (Links to External Site)
Date:  Sep 14 2007
Impact:   Denial of service via local system
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 2.0, 2.1, 3.0, 3.1, 4.0
Description:   A vulnerability was reported in NetBSD. A local user can cause denial of service conditions.

A local user can invoke an ioctl call and pass specially crafted values to the display driver vga_allocattr() function to trigger a kernel panic.

Other display driver functions are affected.

Venustech AD-LAB reported this vulnerability.

Impact:   A local user can cause a kernel panic.
Solution:   NetBSD has issued a fix.

The NetBSD advisory is available at:

Vendor URL: (Links to External Site)
Cause:   Boundary error

Message History:   None.

 Source Message Contents

Subject:  NetBSD Security Advisory 2007-006: Local panics in display driver code

Hash: SHA1

		 NetBSD Security Advisory 2007-006

Topic:		Local panics in display driver code

Version:	NetBSD-current:	source prior to July 28, 2007
		NetBSD 4.0_BETA2	affected
		NetBSD 3.1:		affected
		NetBSD 3.0.*:		affected
		NetBSD 3.0:		affected
		NetBSD 2.1:		not affected
		NetBSD 2.0.*:		not affected
		NetBSD 2.0:		not affected

Severity:	Local system crash 

Fixed:		NetBSD-current:		July 28, 2007
		NetBSD-4 branch:	July 30, 2007
			(4.0 will include the fix)
		NetBSD-3-1 branch	August 6, 2007
			(3.1.1 will include the fix)
		NetBSD-3-0 branch:	August 6, 2007
			(3.0.3 will include the fix)
		NetBSD-3 branch:	August 6, 2007


A local user can cause the system to panic by passing out of bounds
values to display driver allocattr functions via an ioctl call.

This vulnerability has been assigned CVE reference CVE-2007-3654.

Technical Details

vga_allocattr uses integer arguments as indicies into arrays of colors.
The vga_allocattr function does not check to see whether these arguments
are within the bounds of the arrays. 

Due to the lack of bounds checking a negative or large value can be passed
to vga_allocattr which will cause it to access arbitrary memory locations,
resulting in a panic. 

Other display driver functions are also vulnerable to this issue.

Solutions and Workarounds

To rectify these problems a kernel built from sources containing the
fixes must be installed and the system rebooted.

The following instructions describe how to upgrade your kernel
by updating your source tree and rebuilding and installing a new version
of the kernel.

For more information on how to do this, see:

* NetBSD-current:

	Systems running NetBSD-current dated from before 2007-07-28
	should be upgraded to NetBSD-current dated 2007-07-29 or later.

	The following files need to be updated from the
	netbsd-current CVS branch (aka HEAD):

	To update from CVS, re-build, and re-install a kernel containing
	the fix:

		# cd src
		# cvs update -d -P sys/dev
		# tools kernel=KERNCONFFILE

* NetBSD 3.*:

	Systems running NetBSD 3.* sources dated from before
	2007-08-06 should be upgraded from NetBSD 3.* sources dated
	2007-08-07 or later.

	The following files need to be updated from the
	netbsd-3, netbsd-3-0 or netbsd-3-1 branches:

	To update from CVS, re-build, and re-install a kernel containing
	the fix:

		# cd src
		# cvs update -r <branch_name> sys/dev/ic/pcdisplay_subr.c
		# cvs update -r <branch_name> sys/dev/ic/vga.c
		# cvs update -r <branch_name> sys/dev/ic/vga_raster.c
		# cvs update -r <branch_name> sys/dev/isa/ega.c
		# cvs update -r <branch_name> sys/dev/rasops/rasops.c
		# tools kernel=KERNCONFFILE

Thanks To

Venustech AD-LAB for discovering and reporting this problem.

Revision History

	2007-09-13	Initial release

More Information

Advisories may be updated as new information becomes available.
The most recent version of this advisory (PGP signed) can be found at

Information about NetBSD and NetBSD security can be found at and

Copyright 2007, The NetBSD Foundation, Inc.  All Rights Reserved.
Redistribution permitted only in full, unmodified form.

$NetBSD: rt14768_vga.txt,v 1.7 2007/08/14 21:59:52 adrianp Exp $

Version: GnuPG v1.4.7 (NetBSD)



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