RHSA-2015:2587 - Security Advisory

Topic

Updated kernel packages that fix three security issues, several bugs, and
one enhancement are now available for Red Hat Enterprise Linux 7.1 Extended
Update Support.

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.

• A flaw was found in the way the Linux kernel's file system implementation

handled rename operations in which the source was inside and the
destination was outside of a bind mount. A privileged user inside a
container could use this flaw to escape the bind mount and, potentially,
escalate their privileges on the system. (CVE-2015-2925, Important)

• 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) is handled.
A privileged user inside a guest could use this flaw to create denial of
service conditions on the host kernel. (CVE-2015-5307, Important)

• A race condition flaw was found in the way the Linux kernel's IPC

subsystem initialized certain fields in an IPC object structure that were
later used for permission checking before inserting the object into a
globally visible list. A local, unprivileged user could potentially use
this flaw to elevate their privileges on the system. (CVE-2015-7613,
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 and adds one enhancement:

• When setting up an ESP IPsec connection, the aes_ctr algorithm did not

work for ESP on a Power little endian VM host. As a consequence, a kernel
error was previously returned and the connection failed to be established.
A set of patches has been provided to fix this bug, and aes_ctr works for
ESP in the described situation as expected. (BZ#1247127)

• The redistribute3() function distributed entries across 3 nodes. However,

some entries were moved an incorrect way, breaking the ordering. As a
result, BUG() in the dm-btree-remove.c:shift() function occurred when
entries were removed from the btree. A patch has been provided to fix this
bug, and redistribute3() now works as expected. (BZ#1263945)

• When booting an mpt2sas adapter in a huge DDW enabled slot on Power, the

kernel previously generated a warning followed by a call trace.
The provided patch set enhances the Power kernel to be able to support
IOMMU as a fallback for the cases where the coherent mask of the device is
not suitable for direct DMA. As a result, neither the warning nor the call
trace occur in this scenario. (BZ#1267133)

• If the client mounted /exports and tried to execute the "chown -R"

command across the entire mountpoint, a warning about a circular directory
structure was previously returned because mount points all had the same
inode number. A set of patches has been provided to fix this bug, and mount
points are now assigned with unique inode numbers as expected. (BZ#1273239)

• Due to a validation error of in-kernel 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#1275149)

• The NFS client could previously fail to send a CLOSE operation if the

file was opened with O_WRONLY and the server restarted after the OPEN.
Consequently, the server appeared in a state that could block other NFS
operations from completing. The client's state flags have been modified to
catch this condition and correctly CLOSE the file. (BZ#1275298)

• This update sets multicast filters for multicast packets when the

interface is not in promiscuous mode. This change has an impact on the RAR
usage such that SR-IOV has some RARs reserved for its own usage as well.
(BZ#1265091)

All kernel users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues and add this
enhancement. 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 for x86_64 - Extended Update Support 7.1 x86_64
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.1 s390x
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.1 ppc64
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.1 ppc64le
• Red Hat Enterprise Linux EUS Compute Node 7.1 x86_64

Fixes

• BZ - 1209367 - CVE-2015-2925 Kernel: vfs: Do not allow escaping from bind mounts
• BZ - 1268270 - CVE-2015-7613 kernel: Unauthorized access to IPC objects with SysV shm
• BZ - 1277172 - CVE-2015-5307 virt: guest to host DoS by triggering an infinite loop in microcode via #AC exception

CVEs

• CVE-2015-2925
• CVE-2015-5307
• CVE-2015-7613

References

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