RHBA-2018:1834 - Bug Fix Advisory

Topic

Updated kernel packages that fix five bugs are now available for Red Hat
Enterprise Linux 6.5 Advanced Update Support.

Description

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

This update fixes the following bugs:

• Previously, an erroneous code in the x86 kexec system call path caused a memory corruption. As a consequence, the system became unresponsive with the following kernel stack trace:

'WARNING: CPU: 13 PID: 36409 at lib/list_debug.c:59 __list_del_entry+0xa1/0xd0 list_del corruption. prev->next should be ffffdd03fddeeca0, but was (null)'

The underlying source code has been fixed so that the memory is no longer corrupted. As a result, the operating system no longer hangs. (BZ#1573180)

• Previously, the support of the Page Table Isolation (PTI) kernel feature on the 32-bit Intel architecture kernels introduced conflicts between the kernel entry code and the kernel debugger. As a consequence, the debugger was not able to pause correctly. This update fixes the kernel entry code not to conflict with the debugger. As a result, the debugger now works correctly as before the support of PTI. (BZ#1577782)
• The support of the Page Table Isolation (PTI) kernel feature on the 32-bit Intel architecture kernels introduced a change in the kernel stack handling. However, the vm86 system call was not modified accordingly. As a consequence, calling vm86 led to a kernel panic. This update modifies the vm86 code to work well with the right kernel stack. As a result, vm86 no longer causes the kernel panic. (BZ#1577788)
• Previously, microcode updates on 32 and 64-bit AMD and Intel architectures were not synchronized. As a consequence, it was not possible to apply the microcode updates. This fix adds the synchronization to the microcode updates so that processors of the stated architectures receive updates at the same time. As a result, microcode updates are now synchronized. (BZ#1578306)
• The initial Speculative Store Bypass Disable (SSBD) mitigation on AMD 32 and 64-bit architecture kernels required the use of a non-architectural model-specific register (MSR) that was not supported by KVM. As a consequence, SSBD caused a fault in the boot process inside of a virtual machine (VM) guest. Subsequently, the operating system was not able to handle the fault gracefully and the kernel panicked. This update temporarily disables SSBD mitigation for the AMD 32 and 64-bit architecture kernels when running as a VM guest. As a result, the kernel no longer panics. Note that the engineering team is going to re-enable the SSBD mitigation in the future version of AMD 32 and 64-bit architecture kernels. (BZ#1582422)

Users of kernel are advised to upgrade to these updated packages, which fix
these bugs. The system must be rebooted for this update to take effect.

Solution

Before applying this update, make sure all previously released errata relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258

Affected Products

• Red Hat Enterprise Linux Server - AUS 6.5 x86_64

Fixes

CVEs

(none)

References

(none)