(RHSA-2019:0202) Moderate: kernel security and bug fix update

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

Security Fix(es):

• kernel: userfaultfd bypasses tmpfs file permissions (CVE-2018-18397)

For more details about the security issue(s), including the impact, a CVSS score, and other related information, refer to the CVE page(s) listed in the References section.

Bug Fix(es):

• When applying two instances of the kprobe debugging mechanism to the same function, one of the kprobes in some cases failed, depending on the kernel address space layout. Consequently, a kprobe registration error occurred. This update fixes the bug in the kprobes registration code to properly detect and handle ftrace-based kprobes. As a result, both kprobes now apply successfully in the described scenario. (BZ#1647815)

• Under heavy mad packet load, the SELinux checks in the mad packet queries for InfiniBand (IB) fabrics significantly increased the mad packet execution time. Consequently, if a single machine was executing a large perfquery to the IB switches of a High Performance (HPC) fabric, mad_rpc timeouts occurred, and the query failed even with SELinux disabled. This update eliminates the SELinux checks when SELinux is disabled. As a result, the mad packet queries through perfquery now have their original run times when SELinux is disabled. (BZ#1648810)

• Previously, a file-system shutdown process caused by an I/O error could race against a running fstrim process to acquire a xfs buffer lock. Consequently, the file-system shutdown process never completed due to a deadlock and the file-system became unresponsive, unable to be unmounted. This update fixes the lock ordering so that the deadlock no longer occurs and the file-system shutdown process now completes in the described scenario. (BZ#1657142)