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HistoryMar 22, 2016 - 12:00 a.m.

(RHSA-2016:0494) Moderate: kernel security, bug fix, and enhancement update






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

  • It was found that the fix for CVE-2015-1805 incorrectly kept buffer
    offset and buffer length in sync on a failed atomic read, potentially
    resulting in a pipe buffer state corruption. A local, unprivileged user
    could use this flaw to crash the system or leak kernel memory to user
    space. (CVE-2016-0774, Moderate)

The security impact of this issue was discovered by Red Hat.

This update also fixes the following bugs:

  • In the anon_vma structure, the degree counts number of child anon_vmas
    and of VMAs which points to this anon_vma. Failure to decrement the
    parent’s degree in the unlink_anon_vma() function, when its list was empty,
    previously triggered a BUG_ON() assertion. The provided patch makes sure
    the anon_vma degree is always decremented when the VMA list is empty, thus
    fixing this bug. (BZ#1318364)

  • When running Internet Protocol Security (IPSEC) on external storage
    encrypted with LUKS under a substantial load on the system, data
    corruptions could previously occur. A set of upstream patches has been
    provided, and data corruption is no longer reported in this situation.

  • Due to prematurely decremented calc_load_task, the calculated load
    average was off by up to the number of CPUs in the machine. As a
    consequence, job scheduling worked improperly causing a drop in the system
    performance. This update keeps the delta of the CPU going into NO_HZ idle
    separately, and folds the pending idle delta into the global active count
    while correctly aging the averages for the idle-duration when leaving NO_HZ
    mode. Now, job scheduling works correctly, ensuring balanced CPU load.

  • Due to a regression in the Red Hat Enterprise Linux 6.7 kernel, the
    cgroup OOM notifier accessed a cgroup-specific internal data structure
    without a proper locking protection, which led to a kernel panic. This
    update adjusts the cgroup OOM notifier to lock internal data properly,
    thus fixing the bug. (BZ#1302763)

  • GFS2 had a rare timing window that sometimes caused it to reference an
    uninitialized variable. Consequently, a kernel panic occurred. The code has
    been changed to reference the correct value during this timing window, and
    the kernel no longer panics. (BZ#1304332)

  • Due to a race condition whereby a cache operation could be submitted
    after a cache object was killed, the kernel occasionally crashed on systems
    running the cachefilesd service. The provided patch prevents the race
    condition by adding serialization in the code that makes the object
    unavailable. As a result, all subsequent operations targetted on the object
    are rejected and the kernel no longer crashes in this scenario.

This update also adds this enhancement:

  • The lpfc driver has been updated to version (BZ#1297838)

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.