Protect yourself against future threats.
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===========================================================================
AUSCERT External Security Bulletin Redistribution
ESB-2014.2030
Multiple vulnerabilities in the mount system call
4 November 2014
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: kernel
Publisher: NetBSD
Operating System: NetBSD
Impact/Access: Denial of Service -- Existing Account
Resolution: Patch/Upgrade
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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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