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Description of problem: When using Kerberos authentication, slow performance and high CPU utilisation may be seen when performing Kerberos operations, such as creating a keytab using the net process or authenticating an NFSv4 mount using rpc.svcgssd.
Version-Release number of selected component (if applicable):
pam_krb5-2.3.11-9.el6.x86_64
krb5-libs-1.9-33.el6.x86_64
krb5-workstation-1.9-33.el6.x86_64
selinux-policy-3.7.19-155.el6_3.noarch
selinux-policy-targeted-3.7.19-155.el6_3.noarch
libselinux-2.0.94-5.3.el6.x86_64
How reproducible:
Install and configure kerberos and run the following commands:
- net ads join
- net ads keytab create
- net ads keytab add
or try to authenticate an NFSv4/Kerberos export.
Occurs when /etc/sysconfig/selinux SELINUX= set to enforcing or permissive, but not disabled.
Actual results:
# time net ads keytab add nfs -U username
real 1m50.321s
user 1m29.677s
sys 0m8.704s
Expected results:
# time net ads keytab add nfs -U username
real 0m4.402s
user 0m0.020s
sys 0m0.012s
Additional info:
Seen in top:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2176 root 20 0 183m 5872 4612 R 99.9 0.1 2:20.60 net
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3392 root 20 0 533m 498m 1540 R 99.7 6.4 0:08.55 rpc.svcgssd
This also causes extremely slow boot or non-bootable system.
strace reveals a lot od SELinux traffic.
Looks similar. Could be libkrb5 and its selinux integration.
SELINUX=disabled resolves the issue.
SELINUX=enforcing or even SELINUX=permissive and the issue still exists.