RHSA-2015:2401 - Security Advisory

Topic

Updated grub2 packages that fix one security issue, several bugs, and add
one enhancement are now available for Red Hat Enterprise Linux 7.

Red Hat Product Security has rated this update as having Low security
impact. A Common Vulnerability Scoring System (CVSS) base score, which
gives a detailed severity rating, is available from the CVE link in the
References section.

Description

The grub2 packages provide version 2 of the Grand Unified Bootloader
(GRUB), a highly configurable and customizable bootloader with modular
architecture. The packages support a variety of kernel formats, file
systems, computer architectures, and hardware devices.

It was discovered that grub2 builds for EFI systems contained modules that
were not suitable to be loaded in a Secure Boot environment. An attacker
could use this flaw to circumvent the Secure Boot mechanisms and load
non-verified code. Attacks could use the boot menu if no password was set,
or the grub2 configuration file if the attacker has root privileges on the
system. (CVE-2015-5281)

This update also fixes the following bugs:

• In one of the earlier updates, GRUB2 was modified to escape forward slash

(/) characters in several different places. In one of these places, the
escaping was unnecessary and prevented certain types of kernel command-line
arguments from being passed to the kernel correctly. With this update,
GRUB2 no longer escapes the forward slash characters in the mentioned
place, and the kernel command-line arguments work as expected. (BZ#1125404)

• Previously, GRUB2 relied on a timing mechanism provided by legacy

hardware, but not by the Hyper-V Gen2 hypervisor, to calibrate its timer
loop. This prevented GRUB2 from operating correctly on Hyper-V Gen2.
This update modifies GRUB2 to use a different mechanism on Hyper-V Gen2 to
calibrate the timing. As a result, Hyper-V Gen2 hypervisors now work as
expected. (BZ#1150698)

• Prior to this update, users who manually configured GRUB2 to use the

built-in GNU Privacy Guard (GPG) verification observed the following error
on boot:

alloc magic is broken at [addr]: [value] Aborted.

Consequently, the boot failed. The GRUB2 built-in GPG verification has been
modified to no longer free the same memory twice. As a result, the
mentioned error no longer occurs. (BZ#1167977)

• Previously, the system sometimes did not recover after terminating

unexpectedly and failed to reboot. To fix this problem, the GRUB2 packages
now enforce file synchronization when creating the GRUB2 configuration
file, which ensures that the required configuration files are written to
disk. As a result, the system now reboots successfully after crashing.
(BZ#1212114)

• Previously, if an unconfigured network driver instance was selected and

configured when the GRUB2 bootloader was loaded on a different instance,
GRUB2 did not receive notifications of the Address Resolution Protocol
(ARP) replies. Consequently, GRUB2 failed with the following error message:

error: timeout: could not resolve hardware address.

With this update, GRUB2 selects the network driver instance from which it
was loaded. As a result, ARP packets are processed correctly. (BZ#1257475)

In addition, this update adds the following enhancement:

• Sorting of GRUB2 boot menu has been improved. GRUB2 now uses the

rpmdevtools package to sort available kernels and the configuration file is
being generated correctly with the most recent kernel version listed at the
top. (BZ#1124074)

All grub2 users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues and add this
enhancement.

Solution

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258

Affected Products

• Red Hat Enterprise Linux Server 7 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.7 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.6 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.5 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.4 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.3 x86_64
• Red Hat Enterprise Linux Workstation 7 x86_64
• Red Hat Enterprise Linux Desktop 7 x86_64
• Red Hat Enterprise Linux for Power, big endian 7 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.7 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.6 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.5 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.4 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.3 ppc64
• Red Hat Enterprise Linux for Scientific Computing 7 x86_64
• Red Hat Enterprise Linux Server from RHUI 7 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.7 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.6 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.5 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.4 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.3 x86_64
• Red Hat Enterprise Linux Server - AUS 7.7 x86_64
• Red Hat Enterprise Linux Server - AUS 7.6 x86_64
• Red Hat Enterprise Linux Server - AUS 7.4 x86_64
• Red Hat Enterprise Linux Server - AUS 7.3 x86_64
• Red Hat Enterprise Linux for Power, little endian 7 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.7 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.6 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.5 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.4 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.3 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.2 ppc64le
• Red Hat Enterprise Linux Server - TUS 7.7 x86_64
• Red Hat Enterprise Linux Server - TUS 7.6 x86_64
• Red Hat Enterprise Linux Server - TUS 7.3 x86_64
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.7 ppc64le
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.6 ppc64le
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.4 ppc64le
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.3 ppc64le
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.7 x86_64
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.6 x86_64
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.4 x86_64
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.3 x86_64

Fixes

• BZ - 1001279 - grub2 can't boot new xfs CRC-capable disk format
• BZ - 1124074 - grub2-mkconfig wrong sorting
• BZ - 1125404 - [RHEL 7] grub2 improperly escapes spaces in kernel parameters
• BZ - 1148650 - no docs explaining what config path GRUB expects when netbooting
• BZ - 1177003 - yum reinstall kernel causes duplicate entry in grub menu
• BZ - 1211101 - grub2 fw_path variable is incorrect for x86 EFI network boot: too many path components stripped
• BZ - 1264103 - CVE-2015-5281 grub2: modules built in on EFI builds that allow loading arbitrary code, circumventing secure boot

CVEs

• CVE-2015-5281

References

• http://www.redhat.com/security/updates/classification/#normal