The kernel packages contain the Linux kernel, the core of any Linux operating system.
Prior to this update, if processes that generate interrupts were active during the guest shutdown sequence, the virtio driver in some cases did not correctly clear the interrupts. As a consequence, the guest kernel became unresponsive, which prevented the shutdown from completing. With this update, the virtio driver processes interrupts more effectively, and guests now shut down reliably in the described scenario. (BZ#1323568)
At a process or thread exit, when the Linux kernel undoes any SysV semaphore operations done previously (the ones done using semop with the SEM_UNDO flag), there was a possible flaw and race with another process or thread removing the same semaphore set where the operations occurred, leading to possible use of in-kernel-freed memory and then to possible unpredictable behavior. This bug could be noticed with software which uses IPC SysV semaphores, such as IBM DB2, which for example in certain cases could lead to some of its processes or utilities to get incorrectly stalled in some IPC semaphore operation or syscall after the race or problem happened. A patch has been provided to fix this bug, and the kernel now behaves as expected in the aforementioned scenario. (BZ#1326341)