RHSA-2015:1643 - Security Advisory

Topic

Updated kernel packages that fix one security issue and two bugs are now
available for Red Hat Enterprise Linux 6.4 Advanced Update Support.

Red Hat Product Security has rated this update as having Moderate 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 kernel packages contain the Linux kernel, the core of any Linux
operating system.

• It was found that the Linux kernel's ping socket implementation did not

properly handle socket unhashing during spurious disconnects, which could
lead to a use-after-free flaw. On x86-64 architecture systems, a local user
able to create ping sockets could use this flaw to crash the system.
On non-x86-64 architecture systems, a local user able to create ping
sockets could use this flaw to escalate their privileges on the system.
(CVE-2015-3636, Moderate)

This update also fixes the following bugs:

• Due to bad memory or memory corruption, an isolated BUG_ON(mm->nr_ptes)

was sometimes reported, indicating that not all the page tables allocated
could be found and freed when the exit_mmap() function cleared the user
address space. As a consequence, a kernel panic occurred. To fix this bug,
the BUG_ON() function has been replaced by WARN_ON(), which prevents the
kernel from panicking in the aforementioned situation. (BZ#1235929)

• Previously, it was for the ext4 driver to read a metadata block and use

it without a verification. If the metadata block was corrupted, a kernel
panic could occur. With this update, verification is forced on every buffer
before it is used, which uncovers possible corruption and prevents further
use of the corrupted metadata buffer. (BZ#1242930)

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 - AUS 6.4 x86_64

Fixes

• BZ - 1218074 - CVE-2015-3636 kernel: ping sockets: use-after-free leading to local privilege escalation

CVEs

• CVE-2015-3636

References

• https://access.redhat.com/security/updates/classification/#moderate