The are no changes to apparmor in that range, but that does cover the
kaiser changes. Since there were no apparmor changes and kaiser changes
the kernel userspace memory interaction my guess is that something is
triggering in the copy_from_user when policy is loaded.

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https://bugs.launchpad.net/bugs/1746806

Title:
  sssd appears to crash AWS c5 and m5 instances, cause 100% CPU

Status in cloud-images:
  New
Status in linux package in Ubuntu:
  Confirmed
Status in linux-aws package in Ubuntu:
  Confirmed
Status in sssd package in Ubuntu:
  Confirmed

Bug description:
  After upgrading to the Ubuntu EC2 AMI from 20180126 (specifically
  ami-79873901 in us-west-2) we have seen sssd hard locking c5 and m5
  EC2 instances after starting the service and CPU goes to 100%.

  We do not experience this issue with t2 or c4 instance types and we do
  not see this issue on any instance types using Ubuntu Cloud images
  from 20180109 or before. I have verified that this is kernel related
  as I booted an image that we created using the Ubuntu cloud image from
  20180109 which works fine on a c5. I then did a "apt update && apt
  install --only-upgrade linux-aws && systemctl disable sssd", rebooted
  the server, verified I was on the new kernel and started sssd with
  "systemctl start sssd" and the EC2 instance froze and Cloudwatch CPU
  usage for that instance went to 100%.

  I haven't been able to find much in the syslog, kern.log, journalctl
  logs, etc. The only thing I have been able to find is that when this
  happens I tend to see "^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@" in
  the syslog and sssd log files.  I have attached several log files and
  the output of a "apport-bug /usr/sbin/sssd". Let me know if you need
  anything else to help track this down.

  Thanks,
  Paul

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