(RHSA-2016:1814) Important: kernel security and bug fix update

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

Security Fix(es):

• 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 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)

• It was found that the RFC 5961 challenge ACK rate limiting as implemented in the Linux kernel’s networking subsystem allowed an off-path attacker to leak certain information about a given connection by creating congestion on the global challenge ACK rate limit counter and then measuring the changes by probing packets. An off-path attacker could use this flaw to either terminate TCP connection and/or inject payload into non-secured TCP connection between two endpoints on the network. (CVE-2016-5696, Important)

Red Hat would like to thank Jann Horn for reporting CVE-2016-4565 and Yue Cao (Cyber Security Group of the CS department of University of California in Riverside) for reporting CVE-2016-5696.

Bug Fix(es):

• After upgrading the kernel, CPU load average increased compared to the prior kernel version due to the modification of the scheduler. The provided patchset makes the calculation algorithm of this load average roll back to the status of the previous system version thus resulting in relatively lower values in the same system load. (BZ#1343010)