(RHSA-2016:1406) Important: kernel security and bug fix update

2016-07-12T18:55:11
ID RHSA-2016:1406
Type redhat
Reporter RedHat
Modified 2018-06-06T20:24:34

Description

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

Security Fix:

  • A flaw was found in the way certain interfaces of the Linux kernel's Infiniband subsystem used write() as bi-directional ioctl() replacement, which could lead to insufficient memory security checks when being invoked using the the splice() system call. A local unprivileged user on a system with either Infiniband hardware present or RDMA Userspace Connection Manager Access module explicitly loaded, could use this flaw to escalate their privileges on the system. (CVE-2016-4565, Important)

Red Hat would like to thank Jann Horn for reporting this issue.

This update also fixes the following bugs:

  • When providing some services and using the Integrated Services Digital Network (ISDN), the system could terminate unexpectedly due to the call of the tty_ldisc_flush() function. The provided patch removes this call and the system no longer hangs in the described scenario. (BZ#1337443)

  • An update to the Red Hat Enterprise Linux 6.8 kernel added calls of two functions provided by the ipv6.ko kernel module, which added a dependency on that module. On systems where ipv6.ko was prevented from being loaded, the nfsd.ko and lockd.ko modules were unable to be loaded. Consequently, it was not possible to run an NFS server or to mount NFS file systems as a client. The underlying source code has been fixed by adding the symbol_get() function, which determines if nfsd.ko and lock.ko are loaded into memory and calls them through function pointers, not directly. As a result, the aforementioned kernel modules are allowed to be loaded even if ipv6.ko is not, and the NFS mount works as expected. (BZ#1341496)

  • After upgrading the kernel, CPU load average increased compared to the prior kernel version due to the modification of the scheduler. The provided patch set reverts the calculation algorithm of this load average to the the previous version thus resulting in relatively lower values under the same system load. (BZ#1343015)