RHSA-2015:2552 - Security Advisory

Topic

Updated kernel packages that fix two security issues, 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 Important security
impact. Common Vulnerability Scoring System (CVSS) base scores, which give
detailed severity ratings, are available for each vulnerability from the
CVE links in the References section.

Description

The kernel packages contain the Linux kernel, the core of any Linux
operating system.

• It was found that the x86 ISA (Instruction Set Architecture) is prone to

a denial of service attack inside a virtualized environment in the form of
an infinite loop in the microcode due to the way (sequential) delivering of
benign exceptions such as #AC (alignment check exception) and #DB (debug
exception) is handled. A privileged user inside a guest could use these
flaws to create denial of service conditions on the host kernel.
(CVE-2015-5307, CVE-2015-8104, Important)

Red Hat would like to thank Ben Serebrin of Google Inc. for reporting the
CVE-2015-5307 issue.

This update also fixes the following bugs:

• On Intel Xeon v5 platforms, the processor frequency was always tied to

the highest possible frequency. Switching p-states on these client
platforms failed. This update sets the idle frequency, busy frequency, and
processor frequency values by determining the range and adjusting the
minimal and maximal percent limit values. Now, switching p-states on the
aforementioned client platforms proceeds successfully. (BZ#1273926)

• Due to a validation error of in-kernel memory-mapped I/O (MMIO) tracing,

a VM became previously unresponsive when connected to Red Hat Enterprise
Virtualization Hypervisor. The provided patch fixes this bug by dropping
the check in MMIO handler, and a VM continues running as expected.
(BZ#1275150)

• Due to retry-able command errors, the NVMe driver previously leaked I/O

descriptors and DMA mappings. As a consequence, the kernel could become
unresponsive during the hot-unplug operation if a driver was removed.
This update fixes the driver memory leak bug on command retries, and the
kernel no longer hangs in this situation. (BZ#1279792)

• The hybrid_dma_data() function was not initialized before use, which

caused an invalid memory access when hot-plugging a PCI card. As a
consequence, a kernel oops occurred. The provided patch makes sure
hybrid_dma_data() is initialized before use, and the kernel oops no longer
occurs in this situation. (BZ#1279793)

• When running PowerPC (PPC) KVM guests and the host was experiencing a lot

of page faults, for example because it was running low on memory, the host
sometimes triggered an incorrect kind of interrupt in the guest: a data
storage exception instead of a data segment exception. This caused a kernel
panic of the PPC KVM guest. With this update, the host kernel synthesizes a
segment fault if the corresponding Segment Lookaside Buffer (SLB) lookup
fails, which prevents the kernel panic from occurring. (BZ#1281423)

• The kernel accessed an incorrect area of the khugepaged process causing

Logical Partitioning (LPAR) to become unresponsive, and an oops occurred in
medlp5. The backported upstream patch prevents an LPAR hang, and the oops
no longer occurs. (BZ#1281424)

• When the sctp module was loaded and a route to an association endpoint

was removed after receiving an Out-of-The-Blue (OOTB) chunk but before
incrementing the "dropped because of missing route" SNMP statistic, a Null
Pointer Dereference kernel panic previously occurred. This update fixes the
race condition between OOTB response and route removal. (BZ#1281426)

• The cpuscaling test of the certification test suite previously failed due

to a rounding bug in the intel-pstate driver. This bug has been fixed and
the cpuscaling test now passes. (BZ#1281491)

All kernel users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues. The system must be
rebooted for this update to take effect.

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 for x86_64 - Extended Update Support 7.2 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 Server - AUS 7.2 x86_64
• Red Hat Enterprise Linux Workstation 7 x86_64
• Red Hat Enterprise Linux Desktop 7 x86_64
• Red Hat Enterprise Linux for IBM z Systems 7 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.7 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.6 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.5 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.4 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.3 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.2 s390x
• 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 Power, big endian - Extended Update Support 7.2 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 Server - Extended Life Cycle Support 7 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 - TUS 7.2 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 7 s390x
• 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 EUS Compute Node 7.2 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
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.2 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support for IBM Power, big endian 7 ppc64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support for IBM Power, little endian 7 ppc64le

Fixes

• BZ - 1277172 - CVE-2015-5307 virt: guest to host DoS by triggering an infinite loop in microcode via #AC exception
• BZ - 1278496 - CVE-2015-8104 virt: guest to host DoS by triggering an infinite loop in microcode via #DB exception

CVEs

• CVE-2015-5307
• CVE-2015-8104

References

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