Commit e152c7b7 authored by Alexey Budankov's avatar Alexey Budankov Committed by Jonathan Corbet

perf-security: elaborate on perf_events/Perf privileged users

Elaborate on possible perf_event/Perf privileged users groups
and document steps about creating such groups.
Signed-off-by: default avatarAlexey Budankov <alexey.budankov@linux.intel.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent 68570ca0
...@@ -73,6 +73,48 @@ enable capturing of additional data required for later performance analysis of ...@@ -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 monitored processes or a system. For example, CAP_SYSLOG capability permits
reading kernel space memory addresses from /proc/kallsyms file. 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 who are not in the perf_users group:
::
# 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 the 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 perf_events/Perf unprivileged users
----------------------------------- -----------------------------------
...@@ -162,6 +204,7 @@ Bibliography ...@@ -162,6 +204,7 @@ Bibliography
.. [7] `<http://man7.org/linux/man-pages/man2/ptrace.2.html>`_ .. [7] `<http://man7.org/linux/man-pages/man2/ptrace.2.html>`_
.. [8] `<https://en.wikipedia.org/wiki/Hardware_performance_counter>`_ .. [8] `<https://en.wikipedia.org/wiki/Hardware_performance_counter>`_
.. [9] `<https://en.wikipedia.org/wiki/Model-specific_register>`_ .. [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>`_ .. [11] `<http://man7.org/linux/man-pages/man2/getrlimit.2.html>`_
.. [12] `<http://man7.org/linux/man-pages/man5/limits.conf.5.html>`_ .. [12] `<http://man7.org/linux/man-pages/man5/limits.conf.5.html>`_
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