Bug ID 760680: TMSH may utilize 100% CPU (single core worth) when set to be a process group leader and SSH session is closed.

Last Modified: Sep 17, 2019

Bug Tracker

Affected Product:  See more info
BIG-IP TMOS(all modules)

Known Affected Versions:
14.1.0, 14.1.0.1, 14.1.0.2, 14.1.0.3, 14.1.0.4, 14.1.0.5, 14.1.0.6, 14.1.2, 15.0.0, 15.0.1

Opened: Mar 07, 2019
Severity: 3-Major

Symptoms

TMSH does not correctly handle absence of input stream after closing interactive SSH session and remains active in an infinite loop using 100% CPU.

Impact

The equivalent of one CPU core is utilized to 100% by the TMSH process. It may be mostly scheduled on one core or spread over multiple control plane cores.

Conditions

If TMSH is a process group leader, it will not be killed when the parent shell is terminated upon SSH session close. This is a rare case, as TMSH must be deliberately promoted to a process group leader, e.g., with the 'setsid' command. Usually the shell process is a group leader and, when it is terminated upon SSH session close, it kills its child processes, including TMSH.

Workaround

TMSH should not be intentionally promoted to a process group leader. You can safely kill abandoned TMSH processes using the command: killall tmsh

Fix Information

None

Behavior Change