(RHSA-2018:0502) Important: kernel-alt security and bug fix update

The kernel-alt packages provide the Linux kernel version 4.x.

Security Fix(es):

• hw: cpu: speculative execution permission faults handling (CVE-2017-5754, Important)(ppc only)

• kernel: Race condition in raw_sendmsg function allows denial-of-service or kernel addresses leak (CVE-2017-17712, Important)

• kernel: mm/pagewalk.c:walk_hugetlb_range function mishandles holes in hugetlb ranges causing information leak (CVE-2017-16994, Moderate)

Bug Fix(es):

• When changing the Maximum Transmission Unit (MTU) size on Broadcom BCM5717, BCM5718 and BCM5719 chipsets, the tg3 driver sometimes lost synchronization with the device. Consequently, the device became unresponsive. With this update, tg3 has been fixed, and devices no longer hang due to this behavior. (BZ#1533478)

• Previously, the perf tool used strict string matching to provide related events to a particular CPUID instruction. Consequently, the events were not available on certain IBM PowerPC systems. This update fixes perf to use regular expressions instead of string matching of the entire CPUID string. As a result, the perf tool now supports events on IBM PowerPC architectures as expected. (BZ#1536567)

• Previously, the kernel debugfs file system implemented removal protection based on sleepable read-copy-update (SRCU), which slowed down the drivers relying on the debugfs_remove_recursive() function. Consequently, a decrease in performance or a deadlock sometimes occurred. This update implements per-file removal protection in debugfs. As a result, the performance of the system has improved significantly. (BZ#1538030)

• When running the ‘perf test’ command on a PowerKVM guest multiple times, the branch instructions recorded in Branch History Rolling Buffer (BHRB) entries were sometimes unmapped before the kernel processed the entries. Consequently, the operating system terminated unexpectedly. This update fixes the bug, and the operating system no longer crashes in the described situation. (BZ#1538031)