OracleVM 3.3 : xen (OVMSA-2017-0148)

This script is Copyright (C) 2017 Tenable Network Security, Inc.


Synopsis :

The remote OracleVM host is missing one or more security updates.

Description :

The remote OracleVM system is missing necessary patches to address
critical security updates :

- From: Jan Beulich Subject: gnttab: correct pin status
fixup for copy Regardless of copy operations only
setting GNTPIN_hst*, GNTPIN_dev* also need to be taken
into account when deciding whether to clear
_GTF_[read,writ]ing. At least for consistency with code
elsewhere the read part better doesn't use any mask at
all. This is XSA-230. (CVE-2017-12855)

- From: Andrew Cooper Subject: grant_table: Default to v1,
and disallow transitive grants The reference counting
and locking discipline for transitive grants is broken.
Their use is therefore declared out of security support.
This is XSA-226. Transitive grants are expected to be
unconditionally available with grant table v2. Hiding
transitive grants alone is an ABI breakage for the
guest. Modern versions of Linux and the Windows PV
drivers use grant table v1, but older versions did use
v2. In principle, disabling gnttab v2 entirely is the
safer way to cause guests to avoid using transitive
grants. However, some older guests which defaulted to
using gnttab v2 don't tolerate falling back from v2 to
v1 over migrate. This patch introduces a new command
line option to control grant table behaviour. One
suboption allows a choice of the maximum grant table
version Xen will allow the guest to use, and defaults to
v2. A different suboption independently controls whether
transitive grants can be used. The default case is:
gnttab=max_ver:2 To disable gnttab v2 entirely, use:
gnttab=max_ver:1 To allow gnttab v2 and transitive
grants, use: gnttab=max_ver:2,transitive

Conflict: docs/misc/xen-command-line.markdown
(CVE-2017-12135)

- Revert wrong fix for xsa226 [bug 26567225]

- From 3aab881c7331cf93ffd8d2f2dd9adfd18ed4fc99 Mon Sep 17
00:00:00 2001 From: Andrew Cooper Date: Tue, 20 Jun 2017
19:18:54 +0100 Subject: [PATCH] x86/grant: Disallow
misaligned PTEs Pagetable entries must be aligned to
function correctly. Disallow attempts from the guest to
have a grant PTE created at a misaligned address, which
would result in corruption of the L1 table with
largely-guest-controlled values. This is XSA-227
(CVE-2017-12137)

- Prerequisite patch for xsa227-4.5.patch There is no
macro ASSERT_UNREACHABLE before OVM3.4 which is needed
by xsa227-4.5.patch This chunk is picked from upstream
commit cacdb0faaa121ac8f792d5bd34cc6bc7c72d21da
(CVE-2017-12137)

- From: Jan Beulich Subject: gnttab: don't use possibly
unbounded tail calls There is no guarantee that the
compiler would actually translate them to branches
instead of calls, so only ones with a known recursion
limit are okay :

- __release_grant_for_copy can call itself only once, as
__acquire_grant_for_copy won't permit use of multi-level
transitive grants,

- __acquire_grant_for_copy is fine to call itself with the
last argument false, as that prevents further recursion,

- __acquire_grant_for_copy must not call itself to recover
from an observed change to the active entry's pin count
This is XSA-226. (CVE-2017-12135)

- From 69549b08eb9bd3a525c07a97d952673a3d02c76a Mon Sep 17
00:00:00 2001 From: Annie Li Date: Fri, 7 Jul 2017
14:36:08 -0400 Subject: [PATCH] xen: increase default
max grant frames and max maptrack frames Commit
9dfba034e increase default max grant frames to 128 which
is still not enough when the guest has more cpus and
vbd/vif devices, so set it to 256. Also the default max
maptrack frames needs to be increased accordingly.

See also :

http://www.nessus.org/u?e4f463c5

Solution :

Update the affected xen / xen-tools packages.

Risk factor :

High / CVSS Base Score : 7.2
(CVSS2#AV:L/AC:L/Au:N/C:C/I:C/A:C)
CVSS Temporal Score : 5.3
(CVSS2#E:U/RL:OF/RC:C)
Public Exploit Available : false

Family: OracleVM Local Security Checks

Nessus Plugin ID: 102906 ()

Bugtraq ID:

CVE ID: CVE-2017-12135
CVE-2017-12137
CVE-2017-12855

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