PH46918: MOUNTING VOBS IN AUTOMATIC VIEWS CAUSES A KERNEL PANIC IN SUPERVISOR MODE ACCESS PROTECTION (SMAP) - ENABLED LINUX HOSTS

APAR status

• Closed as program error.

Error description

• Any attempt to mount a VOB in an automatic view will cause a
  system crash on any Linux host with a CPU capable of Supervisor
  Mode access protection. I.e., any 6th-generation-or-later Intel
  Core CPU.
  
  Mounting VOBs in dynamic views does not cause a system crash,
  only in automatic views.
  

Local fix

• If using QEMU/KVM hypervisor guests, disable smap as part of the
  guest startup. Specifics depend on how the VM is started.
  If a non-virtual host, disable smap as part of the kernel boot
  process. See
  https://stackoverflow.com/questions/55615925/how-can-i-enable-di
  sable-kernel-kaslr-smep-and-smap
  If using a VMWare VM, you can modifiy the cpu flags according to
  https://news.ycombinator.com/item?id=14084148
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * Users of ClearCase automatic views on Linux                  *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * When running on a Linux host with Supervisor Mode Access     *
  * Protection (SMAP) enabled, mounting a ClearCase VOB for use  *
  * in an automatic view  may cause a system crash.              *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  

Problem conclusion

• Code which checks the VOB mount options was updated to be
  compliant with access protection checking.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  CLEARCASE WIN

• Fixed component ID

  5724G2900

Applicable component levels