On Fri, 1 Feb 2019 10:30:58 +0300 Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx> wrote: > 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 Since we're giving basic sysadmin info here, we should probably say explicitly that this will block access to the perf binary to anybody who is not in the perf_users group. > +2. Assign required capabilities to the Perf tool executable file and enable Assign *the* required > + 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 Why the *emphasis* here? We prefer to minimize this kind of markup whenever possible. Thanks, jon
