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Category:   OS (UNIX)  >   NetBSD Vendors:   NetBSD
NetBSD Flaws in Mount System Call Let Local Users Deny Service
SecurityTracker Alert ID:  1031155
SecurityTracker URL:  http://securitytracker.com/id/1031155
CVE Reference:   GENERIC-MAP-NOMATCH   (Links to External Site)
Date:  Nov 3 2014
Impact:   Denial of service via local system
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 5.1, 5.2, 6.0, 6.1
Description:   A vulnerability was reported in NetBSD. A local user can cause denial of service conditions.

A local user can supply specially crafted arguments to the mount system call to trigger one of several buffer allocation errors and cause the target system to crash.

Maxime Villard reported this vulnerability.

Impact:   A local user can cause the target kernel to crash.
Solution:   The vendor has issued a fix.

The vendor's advisory is available at:

http://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2014-014.txt.asc

Vendor URL:  ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2014-014.txt.asc (Links to External Site)
Cause:   Boundary error

Message History:   None.


 Source Message Contents

Subject:  NetBSD Security Advisory 2014-014: Multiple vulnerabilities in the mount system call

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

		NetBSD Security Advisory 2014-014
		=================================

Topic:		Multiple vulnerabilities in the mount system call


Version:	NetBSD-current:		source prior to Sun, Apr 20th 2014
		NetBSD 6.1.5:		not affected
		NetBSD 6.1 - 6.1.4:	affected
		NetBSD 6.0.6:		not affected
		NetBSD 6.0 - 6.0.5:	affected
		NetBSD 5.1 - 5.1.4:	affected
		NetBSD 5.2 - 5.2.2:	affected

Severity:	Local DoS

Fixed:		NetBSD-current:		Sun, Apr 20th 2014
		NetBSD-6-0 branch:	Mon, 21 Apr 2014
		NetBSD-6-1 branch:	Mon, 21 Apr 2014
		NetBSD-6 branch:	Mon, 21 Apr 2014
		NetBSD-5-2 branch:	Tue, 29 Apr 2014
		NetBSD-5-1 branch:	Tue, 29 Apr 2014
		NetBSD-5 branch:	Sat, 26 Apr 2014

Teeny versions released later than the fix date will contain the fix.

Please note that NetBSD releases prior to 5.1 are no longer supported.
It is recommended that all users upgrade to a supported release.


Abstract
========

Due to:
	- missing input validation checks in the mount syscall
	- a wrong assumption on the file systems side
	- a memory corruption bug
the kernel could:
	- allocate an unbounded or zero-sized memory buffer
	- dereference a NULL pointer
	- behave unexpectedly


Technical Details
=================

The mount syscall takes as fourth and fifth arguments an input buffer
and its size. A kernel buffer of the same size is allocated via kmem,
and is then handed over to the appropriate file system. This buffer is
then freed when no longer needed.

The checks on the size of the kernel-allocated buffer were not strict
enough, and a local user could easily make the kernel perform a zero-
sized or unbounded memory allocation, resulting in a crash.

Also, in particular cases, the buffer pointer given to the underlying
file systems is allowed to be NULL - some file systems don't need it.
The others didn't explicitly check for NULL, and were wrongly making the
assumption that it was always a valid, readable buffer, causing the
kernel to panic with a page fault.

Finally, a bug could corrupt memory when freeing the kernel-allocated
buffer. The buffer is freed via kmem_free, whose second argument
indicates the size of the allocated buffer. This size was held by a
local variable which was modified by the underlying file systems, thus
creating a memory inconsistency when freeing which could lead to a
crash or unexpected behavior.


Solutions and Workarounds
=========================

For all NetBSD versions, you need to obtain fixed kernel sources,
rebuild and install the new kernel, and reboot the system.
                                      
The fixed source may be obtained from the NetBSD CVS repository.        
The following instructions briefly summarise how to upgrade your        
kernel.  In these instructions, replace:

  ARCH     with your architecture (from uname -m),               
  KERNCONF with the name of your kernel configuration file and  
  VERSION  with the file version below

File versions containing the fixes:

files relative to src/sys/fs/:

 HEAD  netbsd-6  netbsd-6-1    netbsd-6-0    netbsd-5   netbsd-5-2    netbsd-5-1
 ----  --------  ----------    ----------    --------   ----------    ----------
adosfs/advfsops.c
 1.70  1.63.6.1  1.63.12.1     1.63.10.1     1.53.6.1   1.53.20.1     1.53.16.1
cd9660/cd9660_vfsops.c
 1.84  1.74.6.1  1.74.12.1     1.74.10.1     1.63.6.2   1.63.6.1.6.1  1.63.6.1.2.1
efs/efs_vfsops.c
 1.25  1.22.8.1  1.22.14.1     1.22.12.1     1.16.4.2   1.16.4.1.10.1 1.16.4.1.6.1
filecorefs/filecore_vfsops.c
 1.76  1.68.6.1  1.68.12.1     1.68.10.1     1.55.6.1   1.55.20.1     1.55.16.1
hfs/hfs_vfsops.c
 1.31  1.27.8.2  1.27.8.1.6.1  1.27.8.1.4.1  1.19.4.1   1.19.16.1     1.19.12.1
msdosfs/msdosfs_vfsops.c
 1.107 1.93.6.2  1.93.6.1.6.1  1.93.6.1.4.1  1.68.6.3   1.68.6.2.10.1 1.68.6.2.6.1
nilfs/nilfs_vfsops.c
 1.16  1.8.6.1   1.8.12.1      1.8.10.1      n/a        n/a           n/a
ntfs/ntfs_vfsops.c
 1.94  1.87.6.1  1.87.20.1     1.87.12.1     1.72.6.2   1.72.6.1.6.1  1.72.6.1.2.1
ptyfs/ptyfs_vfsops.c
 1.50  1.42.18.2 1.42.18.1.4.1 1.42.18.1.2.1 1.37.4.1   1.37.18.1     1.37.14.1
puffs/puffs_vfsops.c
 1.110 1.100.8.3 1.100.8.2.6.1 1.100.8.2.4.1 1.81.8.4   1.81.8.3.2.1  1.81.8.1.2.1
smbfs/smbfs_vfsops.c
 1.100 1.95.8.1  1.95.22.1     1.95.14.1     1.85.4.2   1.85.4.1.6.1  1.85.4.1.2.1
sysvbfs/sysvbfs_vfsops.c
 1.43  1.38.6.2  1.38.6.1.6.1  1.38.6.1.4.1  1.26.4.1   1.26.18.1     1.26.14.1
tmpfs/tmpfs_vfsops.c
 1.59  1.52.8.1  1.52.22.1     1.52.14.1     1.44.4.1   1.44.22.1     1.44.18.1
udf/udf_vfsops.c
 1.67  1.62.6.1  1.62.12.1     1.62.10.1     1.52.2.4   1.52.2.3.6.1  1.52.2.3.2.1
union/union_vfsops.c
 1.72  1.67.2.1  1.67.8.1      1.67.6.1      1.57.6.3   1.57.6.2.2.1  1.57.6.1.6.1
unionfs/unionfs_vfsops.c
 1.13  1.9.10.1  1.9.18.1      1.9.16.1      1.5.6.1    1.5.16.1      1.5.12.1
v7fs/v7fs_vfsops.c
 1.10  1.5.6.2   1.5.6.1.6.1   1.5.6.1.4.1   n/a        n/a           n/a

files relative to src/sys/miscfs/:

 HEAD  netbsd-6  netbsd-6-1    netbsd-6-0    netbsd-5   netbsd-5-2    netbsd-5-1
 ----  --------  ----------    ----------    --------   ----------    ----------
nullfs/null_vfsops.c
 1.88  1.83.14.1 1.83.20.1     1.83.18.1     1.77.6.1   1.77.16.1     1.77.12.1
overlay/overlay_vfsops.c
 1.61  1.56.14.1 1.56.20.1     1.56.18.1     1.53.6.1   1.53.16.1     1.53.12.1
procfs/procfs_vfsops.c
 1.91  1.86.8.1  1.86.14.1     1.86.12.1     1.81.6.1   1.81.20.1     1.81.16.1
umapfs/umap_vfsops.c
 1.92  1.86.14.1 1.86.20.1     1.86.18.1     1.80.6.1   1.80.16.1     1.80.12.1

files relative to src/sys/ufs/:

 HEAD  netbsd-6  netbsd-6-1    netbsd-6-0    netbsd-5   netbsd-5-2    netbsd-5-1
 ----  --------  ----------    ----------    --------   ----------    ----------
chfs/chfs_vfsops.c
 1.11  1.2.4.1   1.2.10.1      1.2.8.1       n/a        n/a           n/a
ext2fs/ext2fs_vfsops.c
 1.180 1.162.6.1 1.162.12.1    1.162.10.1    1.137.6.7  1.137.6.6.2.1 1.137.6.5.2.1
ffs/ffs_vfsops.c
 1.297 1.275.2.3 1.275.2.2.4.1 1.275.2.2.2.1 1.239.2.5  1.239.2.4.6.1 1.239.2.4.2.1
lfs/lfs_vfsops.c
 1.321 1.293.2.2 1.293.2.1.6.1 1.293.2.1.4.1 1.267.6.2  1.267.6.1.10.1
                                                                      1.267.6.1.6.1
mfs/mfs_vfsops.c
 1.107 1.103.8.1 1.103.22.1    1.103.14.1    1.98.6.1   1.98.16.1     1.98.12.1

remaining files:

 HEAD  netbsd-6  netbsd-6-1    netbsd-6-0    netbsd-5   netbsd-5-2    netbsd-5-1
 ----  --------  ----------    ----------    --------   ----------    ----------
src/external/cddl/osnet/dist/uts/common/fs/zfs/zfs_vfsops.c
 1.12  1.7.2.1   1.7.10.1      1.7.8.1       n/a        n/a           n/a
src/sys/coda/coda_vfsops.c
 1.81  1.70.8.1  1.70.14.1     1.70.12.1     1.66.8.1   1.66.22.1     1.66.18.1
src/sys/kern/vfs_syscalls.c
 1.482 1.449.2.3 1.449.2.2.6.1 1.449.2.2.4.1 1.376.4.8  1.376.4.7.2.1 1.376.4.5.2.2
src/sys/nfs/nfs_vfsops.c
 1.227 1.220.8.1 1.220.16.1    1.220.14.1    1.203.4.1  1.203.14.1    1.203.10.1


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

	# cd src
	# cvs update -d -P -r VERSION \
		external/cddl/osnet/dist/uts/common/fs/zfs/zfs_vfsops.c
	# cvs update -d -P -r VERSION sys/coda/coda_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/adosfs/advfsops.c
	# cvs update -d -P -r VERSION sys/fs/cd9660/cd9660_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/efs/efs_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/filecorefs/filecore_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/hfs/hfs_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/msdosfs/msdosfs_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/nilfs/nilfs_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/ntfs/ntfs_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/ptyfs/ptyfs_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/puffs/puffs_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/smbfs/smbfs_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/sysvbfs/sysvbfs_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/tmpfs/tmpfs_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/udf/udf_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/union/union_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/unionfs/unionfs_vfsops.c
	# cvs update -d -P -r VERSION sys/fs/v7fs/v7fs_vfsops.c
	# cvs update -d -P -r VERSION sys/kern/vfs_syscalls.c
	# cvs update -d -P -r VERSION sys/miscfs/nullfs/null_vfsops.c
	# cvs update -d -P -r VERSION sys/miscfs/overlay/overlay_vfsops.c
	# cvs update -d -P -r VERSION sys/miscfs/procfs/procfs_vfsops.c
	# cvs update -d -P -r VERSION sys/miscfs/umapfs/umap_vfsops.c
	# cvs update -d -P -r VERSION sys/nfs/nfs_vfsops.c
	# cvs update -d -P -r VERSION sys/ufs/chfs/chfs_vfsops.c
	# cvs update -d -P -r VERSION sys/ufs/ext2fs/ext2fs_vfsops.c
	# cvs update -d -P -r VERSION sys/ufs/ffs/ffs_vfsops.c
	# cvs update -d -P -r VERSION sys/ufs/lfs/lfs_vfsops.c
	# cvs update -d -P -r VERSION sys/ufs/mfs/mfs_vfsops.c
	# ./build.sh kernel=KERNCONF
	# mv /netbsd /netbsd.old
	# cp sys/arch/ARCH/compile/obj/KERNCONF/netbsd /netbsd 
	# shutdown -r now

For more information on how to do this, see:    

   http://www.NetBSD.org/guide/en/chap-kernel.html


Thanks To
=========

Thanks to Maxime Villard, Christos Zoulas and matthew green; Maxime Villard
for finding the issues and all three for developing fixes.


Note
====

It is to be noted that despite the long, unusual time the NetBSD Foundation
took to release this Security Advisory, the fixes listed above were applied
and propagated to the stable branches as soon as the vulnerabilities were
discovered.


Revision History
================

	2014-11-03	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 
  http://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2014-014.txt.asc

Information about NetBSD and NetBSD security can be found at
http://www.NetBSD.org/ and http://www.NetBSD.org/Security/ .


Copyright 2014, The NetBSD Foundation, Inc.  All Rights Reserved.
Redistribution permitted only in full, unmodified form.

$NetBSD: NetBSD-SA2014-014.txt,v 1.2 2014/11/03 09:09:54 spz Exp $

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