Elaborate on possible perf_event/Perf privileged users groups and document steps about creating such groups. Signed-off-by: Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx> --- Documentation/admin-guide/perf-security.rst | 43 +++++++++++++++++++++ 1 file changed, 43 insertions(+) diff --git a/Documentation/admin-guide/perf-security.rst b/Documentation/admin-guide/perf-security.rst index 7da7fa459718..fe90f8952be9 100644 --- a/Documentation/admin-guide/perf-security.rst +++ b/Documentation/admin-guide/perf-security.rst @@ -73,6 +73,48 @@ enable capturing of additional data required for later performance analysis of monitored processes or a system. For example, CAP_SYSLOG capability permits reading kernel space memory addresses from /proc/kallsyms file. +perf_events/Perf privileged users +--------------------------------- + +Mechanisms of capabilities, privileged capability-dumb files [6]_ and file system +ACLs [10]_ can be used to create a dedicated group of perf_events/Perf privileged +users who are permitted to execute performance monitoring without *scope* limits. +The following steps can be taken to create such a group of privileged Perf users. + +1. Create perf_users group of privileged Perf users, assign perf_users group to + Perf tool executable and limit *access* to the executable for other users in + the system: + +:: + + # groupadd perf_users + # ls -alhF + -rwxr-xr-x 2 root root 11M Oct 19 15:12 perf + # chgrp perf_users perf + # ls -alhF + -rwxr-xr-x 2 root perf_users 11M Oct 19 15:12 perf + # chmod o-rwx perf + # ls -alhF + -rwxr-x--- 2 root perf_users 11M Oct 19 15:12 perf + +2. Assign required capabilities to the Perf tool executable file and enable + members of perf_users group with performance monitoring privileges [6]_ : + +:: + + # setcap "cap_sys_admin,cap_sys_ptrace,cap_syslog=ep" perf + # setcap -v "cap_sys_admin,cap_sys_ptrace,cap_syslog=ep" perf + perf: OK + # getcap perf + perf = cap_sys_ptrace,cap_sys_admin,cap_syslog+ep + +As a result, members of perf_users group are capable of conducting performance +monitoring by using functionality of the configured Perf tool executable that, +when executes, passes perf_events subsystem *scope* checks. + +This specific *access* control management is only available to superuser or root +running processes with CAP_SETPCAP, CAP_SETFCAP [6]_ capabilities. + perf_events/Perf unprivileged users ----------------------------------- @@ -156,6 +198,7 @@ Bibliography .. [7] `<http://man7.org/linux/man-pages/man2/ptrace.2.html>`_ .. [8] `<https://en.wikipedia.org/wiki/Hardware_performance_counter>`_ .. [9] `<https://en.wikipedia.org/wiki/Model-specific_register>`_ +.. [10] `<http://man7.org/linux/man-pages/man5/acl.5.html>`_ .. [11] `<http://man7.org/linux/man-pages/man2/getrlimit.2.html>`_ .. [12] `<http://man7.org/linux/man-pages/man5/limits.conf.5.html>`_
