[PATCH v3 0/3] perf: make Perf tool aware of SELinux access control

[PATCH v3 0/3] perf: make Perf tool aware of SELinux access control

[Alexey Budankov]

Changes in v3:
- mention "CAP_PERFMON or CAP_SYS_ADMIN" instead of sole CAP_PERFMON or 
  CAP_SYS_ADMIN capability in the docs and messages to support use case
  of newer Perf tool on kernel w/o CAP_PERFMON
- reverted double new line in "No permission to enable %s event.\n\n"
- updated security.txt content with new messages wording

v2: https://lore.kernel.org/lkml/66f2975b-4a69-b428-7dc5-d9aa40b3c673@linux.intel.com/

Changes in v2:
- implemented minor doc and code changes to substitute CAP_SYS_ADMIN
  with CAP_PERFMON capability;
- introduced Perf doc file with instructions on how to enable and use
  perf_event LSM hooks for mandatory access control to perf_event_open()
  syscall;

v1: https://lore.kernel.org/lkml/b8a0669e-36e4-a0e8-fd35-3dbd890d2170@linux.intel.com/

repo: git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git perf/core
sha1: ee097e8ee56f8867cbbf45fe2a06f6b9e660c39c


Extend Perf tool with the check of /sys/fs/selinux/enforce value and notify 
in case access to perf_event_open() syscall is restricted by the enforced 
SELinux policy settings. See new added security.txt file for exact steps
how the changes look like and how to test the patch set.

---
Alexey Budankov (3):
  perf docs: extend CAP_SYS_ADMIN with CAP_PERFMON where needed
  perf tool: make Perf tool aware of SELinux access control
  perf docs: introduce security.txt file to document related issues

 tools/perf/Documentation/perf-intel-pt.txt |   2 +-
 tools/perf/Documentation/security.txt      | 237 +++++++++++++++++++++
 tools/perf/util/cloexec.c                  |   4 +-
 tools/perf/util/evsel.c                    |  39 ++--
 4 files changed, 264 insertions(+), 18 deletions(-)
 create mode 100644 tools/perf/Documentation/security.txt

-- 
2.24.1

[PATCH v3 1/3] perf docs: extend CAP_SYS_ADMIN with CAP_PERFMON where needed

[Alexey Budankov]

Extend CAP_SYS_ADMIN with CAP_PERFMON in the docs.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
---
 tools/perf/Documentation/perf-intel-pt.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/Documentation/perf-intel-pt.txt b/tools/perf/Documentation/perf-intel-pt.txt
index 456fdcbf26ac..832408a54c1c 100644
--- a/tools/perf/Documentation/perf-intel-pt.txt
+++ b/tools/perf/Documentation/perf-intel-pt.txt
@@ -687,7 +687,7 @@ The v4.2 kernel introduced support for a context switch metadata event,
 PERF_RECORD_SWITCH, which allows unprivileged users to see when their processes
 are scheduled out and in, just not by whom, which is left for the
 PERF_RECORD_SWITCH_CPU_WIDE, that is only accessible in system wide context,
-which in turn requires CAP_SYS_ADMIN.
+which in turn requires CAP_PERFMON or CAP_SYS_ADMIN.
 
 Please see the 45ac1403f564 ("perf: Add PERF_RECORD_SWITCH to indicate context
 switches") commit, that introduces these metadata events for further info.
-- 
2.24.1

[PATCH v3 2/3] perf tool: make Perf tool aware of SELinux access control

[Alexey Budankov]

Implement selinux sysfs check to see the system is in enforcing
mode and print warning message with pointer to check audit logs.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
---
 tools/perf/util/cloexec.c |  4 ++--
 tools/perf/util/evsel.c   | 39 ++++++++++++++++++++++++---------------
 2 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
index a12872f2856a..9c8ec816261b 100644
--- a/tools/perf/util/cloexec.c
+++ b/tools/perf/util/cloexec.c
@@ -65,7 +65,7 @@ static int perf_flag_probe(void)
 		return 1;
 	}
 
-	WARN_ONCE(err != EINVAL && err != EBUSY,
+	WARN_ONCE(err != EINVAL && err != EBUSY && err != EACCES,
 		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
 		  err, str_error_r(err, sbuf, sizeof(sbuf)));
 
@@ -83,7 +83,7 @@ static int perf_flag_probe(void)
 	if (fd >= 0)
 		close(fd);
 
-	if (WARN_ONCE(fd < 0 && err != EBUSY,
+	if (WARN_ONCE(fd < 0 && err != EBUSY && err != EACCES,
 		      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
 		      err, str_error_r(err, sbuf, sizeof(sbuf))))
 		return -1;
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 9fa92649adb4..bf437c059c2b 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2514,32 +2514,41 @@ int perf_evsel__open_strerror(struct evsel *evsel, struct target *target,
 			      int err, char *msg, size_t size)
 {
 	char sbuf[STRERR_BUFSIZE];
-	int printed = 0;
+	int printed = 0, enforced = 0;
 
 	switch (err) {
 	case EPERM:
 	case EACCES:
+		printed += scnprintf(msg + printed, size - printed,
+			"Access to performance monitoring and observability operations is limited.\n");
+
+		if (!sysfs__read_int("fs/selinux/enforce", &enforced)) {
+			if (enforced) {
+				printed += scnprintf(msg + printed, size - printed,
+					"Enforced MAC policy settings (SELinux) can limit access to performance\n"
+					"monitoring and observability operations. Inspect system audit records for\n"
+					"more perf_event access control information and adjusting the policy.\n");
+			}
+		}
+
 		if (err == EPERM)
-			printed = scnprintf(msg, size,
+			printed += scnprintf(msg, size,
 				"No permission to enable %s event.\n\n",
 				perf_evsel__name(evsel));
 
 		return scnprintf(msg + printed, size - printed,
-		 "You may not have permission to collect %sstats.\n\n"
-		 "Consider tweaking /proc/sys/kernel/perf_event_paranoid,\n"
-		 "which controls use of the performance events system by\n"
-		 "unprivileged users (without CAP_PERFMON or CAP_SYS_ADMIN).\n\n"
-		 "The current value is %d:\n\n"
+		 "Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open\n"
+		 "access to performance monitoring and observability operations for users\n"
+		 "without CAP_PERFMON or CAP_SYS_ADMIN Linux capability.\n"
+		 "perf_event_paranoid setting is %d:\n"
 		 "  -1: Allow use of (almost) all events by all users\n"
 		 "      Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK\n"
-		 ">= 0: Disallow ftrace function tracepoint by users without CAP_PERFMON or CAP_SYS_ADMIN\n"
-		 "      Disallow raw tracepoint access by users without CAP_SYS_PERFMON or CAP_SYS_ADMIN\n"
-		 ">= 1: Disallow CPU event access by users without CAP_PERFMON or CAP_SYS_ADMIN\n"
-		 ">= 2: Disallow kernel profiling by users without CAP_PERFMON or CAP_SYS_ADMIN\n\n"
-		 "To make this setting permanent, edit /etc/sysctl.conf too, e.g.:\n\n"
-		 "	kernel.perf_event_paranoid = -1\n" ,
-				 target->system_wide ? "system-wide " : "",
-				 perf_event_paranoid());
+		 ">= 0: Disallow raw and ftrace function tracepoint access\n"
+		 ">= 1: Disallow CPU event access\n"
+		 ">= 2: Disallow kernel profiling\n"
+		 "To make the adjusted perf_event_paranoid setting permanent preserve it\n"
+		 "in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = <setting>)",
+		 perf_event_paranoid());
 	case ENOENT:
 		return scnprintf(msg, size, "The %s event is not supported.",
 				 perf_evsel__name(evsel));
-- 
2.24.1

[PATCH v3 3/3] perf docs: introduce security.txt file to document related issues

[Alexey Budankov]

Publish instructions on how to apply LSM hooks for access control
to perf_event_open() syscall on Fedora distro with Targeted SELinux
policy and then manage access to the syscall.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
---
 tools/perf/Documentation/security.txt | 237 ++++++++++++++++++++++++++
 1 file changed, 237 insertions(+)
 create mode 100644 tools/perf/Documentation/security.txt

diff --git a/tools/perf/Documentation/security.txt b/tools/perf/Documentation/security.txt
new file mode 100644
index 000000000000..4fe3b8b1958f
--- /dev/null
+++ b/tools/perf/Documentation/security.txt
@@ -0,0 +1,237 @@
+Overview
+========
+
+For general security related questions of perf_event_open() syscall usage,
+performance monitoring and observability operations by Perf see here:
+https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html
+
+Enabling LSM based mandatory access control (MAC) to perf_event_open() syscall
+==============================================================================
+
+LSM hooks for mandatory access control for perf_event_open() syscall can be
+used starting from Linux v5.3. Below are the steps to extend Fedora (v31) with
+Targeted policy with perf_event_open() access control capabilities:
+
+1. Download selinux-policy SRPM package (e.g. selinux-policy-3.14.4-48.fc31.src.rpm on FC31)
+   and install it so rpmbuild directory would exist in the current working directory:
+
+   # rpm -Uhv selinux-policy-3.14.4-48.fc31.src.rpm
+
+2. Get into rpmbuild/SPECS directory and unpack the source code:
+
+   # rpmbuild -bp selinux-policy.spec
+
+3. Place patch below at rpmbuild/BUILD/selinux-policy-b86eaaf4dbcf2d51dd4432df7185c0eaf3cbcc02
+   directory and apply it:
+
+   # patch -p1 < selinux-policy-perf-events-perfmon.patch
+   patching file policy/flask/access_vectors
+   patching file policy/flask/security_classes
+   # cat selinux-policy-perf-events-perfmon.patch
+diff -Nura a/policy/flask/access_vectors b/policy/flask/access_vectors
+--- a/policy/flask/access_vectors	2020-02-04 18:19:53.000000000 +0300
++++ b/policy/flask/access_vectors	2020-02-28 23:37:25.000000000 +0300
+@@ -174,6 +174,7 @@
+ 	wake_alarm
+ 	block_suspend
+ 	audit_read
++	perfmon
+ }
+ 
+ #
+@@ -1099,3 +1100,15 @@
+ 
+ class xdp_socket
+ inherits socket
++
++class perf_event
++{
++	open
++	cpu
++	kernel
++	tracepoint
++	read
++	write
++}
++
++
+diff -Nura a/policy/flask/security_classes b/policy/flask/security_classes
+--- a/policy/flask/security_classes	2020-02-04 18:19:53.000000000 +0300
++++ b/policy/flask/security_classes	2020-02-28 21:35:17.000000000 +0300
+@@ -200,4 +200,6 @@
+ 
+ class xdp_socket
+ 
++class perf_event
++
+ # FLASK
+
+4. Get into rpmbuild/SPECS directory and build policy packages from patched sources:
+
+   # rpmbuild --noclean --noprep -ba selinux-policy.spec
+
+   so you have this:
+
+   # ls -alh rpmbuild/RPMS/noarch/
+   total 33M
+   drwxr-xr-x. 2 root root 4.0K Mar 20 12:16 .
+   drwxr-xr-x. 3 root root 4.0K Mar 20 12:16 ..
+   -rw-r--r--. 1 root root 112K Mar 20 12:16 selinux-policy-3.14.4-48.fc31.noarch.rpm
+   -rw-r--r--. 1 root root 1.2M Mar 20 12:17 selinux-policy-devel-3.14.4-48.fc31.noarch.rpm
+   -rw-r--r--. 1 root root 2.3M Mar 20 12:17 selinux-policy-doc-3.14.4-48.fc31.noarch.rpm
+   -rw-r--r--. 1 root root  12M Mar 20 12:17 selinux-policy-minimum-3.14.4-48.fc31.noarch.rpm
+   -rw-r--r--. 1 root root 4.5M Mar 20 12:16 selinux-policy-mls-3.14.4-48.fc31.noarch.rpm
+   -rw-r--r--. 1 root root 111K Mar 20 12:16 selinux-policy-sandbox-3.14.4-48.fc31.noarch.rpm
+   -rw-r--r--. 1 root root  14M Mar 20 12:17 selinux-policy-targeted-3.14.4-48.fc31.noarch.rpm
+
+5. Install SELinux packages from Fedora repo, if not already done so, and
+   update with the patched rpms above:
+
+   # rpm -Uhv rpmbuild/RPMS/noarch/selinux-policy-*
+
+6. Enable SELinux Permissive mode for Targeted policy, if not already done so:
+
+   # cat /etc/selinux/config
+
+   # This file controls the state of SELinux on the system.
+   # SELINUX= can take one of these three values:
+   #     enforcing - SELinux security policy is enforced.
+   #     permissive - SELinux prints warnings instead of enforcing.
+   #     disabled - No SELinux policy is loaded.
+   SELINUX=permissive
+   # SELINUXTYPE= can take one of these three values:
+   #     targeted - Targeted processes are protected,
+   #     minimum - Modification of targeted policy. Only selected processes are protected.
+   #     mls - Multi Level Security protection.
+   SELINUXTYPE=targeted
+
+7. Enable filesystem SELinux labeling at the next reboot:
+
+   # touch /.autorelabel
+
+8. Reboot machine and it will label filesystems and load Targeted policy into the kernel;
+
+9. Login and check that dmesg output doesn't mention that perf_event class is unknown to SELinux subsystem;
+
+10. Check that SELinux is enabled and in Permissive mode
+
+    # getenforce
+    Permissive
+
+11. Turn SELinux into Enforcing mode:
+
+    # setenforce 1
+    # getenforce
+    Enforcing
+
+Opening access to perf_event_open() syscall on Fedora with SELinux
+==================================================================
+
+Access to performance monitoring and observability operations by Perf
+can be limited for superuser or CAP_PERFMON or CAP_SYS_ADMIN privileged
+processes. MAC policy settings (e.g. SELinux) can be loaded into the kernel
+and prevent unauthorized access to perf_event_open() syscall. In such case
+Perf tool provides a message similar to the one below:
+
+   # perf stat
+   Error:
+   Access to performance monitoring and observability operations is limited.
+   Enforced MAC policy settings (SELinux) can limit access to performance
+   monitoring and observability operations. Inspect system audit records for
+   more perf_event access control information and adjusting the policy.
+   Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open
+   access to performance monitoring and observability operations for users
+   without CAP_PERFMON or CAP_SYS_ADMIN Linux capability.
+   perf_event_paranoid setting is -1:
+     -1: Allow use of (almost) all events by all users
+         Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK
+   >= 0: Disallow raw and ftrace function tracepoint access
+   >= 1: Disallow CPU event access
+   >= 2: Disallow kernel profiling
+   To make the adjusted perf_event_paranoid setting permanent preserve it
+   in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = <setting>)
+
+To make sure that access is limited by MAC policy settings inspect system
+audit records using journalctl command or /var/log/audit/audit.log so the
+output would contain AVC denied records related to perf_event:
+
+   # journalctl --reverse --no-pager | grep perf_event
+
+   python3[1318099]: SELinux is preventing perf from open access on the perf_event labeled unconfined_t.
+                                         If you believe that perf should be allowed open access on perf_event labeled unconfined_t by default.
+   setroubleshoot[1318099]: SELinux is preventing perf from open access on the perf_event labeled unconfined_t. For complete SELinux messages run: sealert -l 4595ce5b-e58f-462c-9d86-3bc2074935de
+   audit[1318098]: AVC avc:  denied  { open } for  pid=1318098 comm="perf" scontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tclass=perf_event permissive=0
+
+In order to open access to perf_event_open() syscall MAC policy settings can
+require to be extended. On SELinux system this can be done by loading a special
+policy module extending base policy settings. Perf related policy module can
+be generated using the system audit records about blocking perf_event access.
+Run the command below to generate my-perf.te policy extension file with
+perf_event related rules:
+
+   # ausearch -c 'perf' --raw | audit2allow -M my-perf && cat my-perf.te
+
+   module my-perf 1.0;
+
+   require {
+        type unconfined_t;
+        class perf_event { cpu kernel open read tracepoint write };
+   }
+
+   #============= unconfined_t ==============
+   allow unconfined_t self:perf_event { cpu kernel open read tracepoint write };
+
+Now compile, pack and load my-perf.pp extension module into the kernel:
+
+   # checkmodule -M -m -o my-perf.mod my-perf.te
+   # semodule_package -o my-perf.pp -m my-perf.mod
+   # semodule -X 300 -i my-perf.pp
+
+After all those taken steps above access to perf_event_open() syscall should
+now be allowed by the policy settings. Check access running Perf like this:
+
+   # perf stat
+   ^C
+   Performance counter stats for 'system wide':
+
+         36,387.41 msec cpu-clock                 #    7.999 CPUs utilized
+             2,629      context-switches          #    0.072 K/sec
+                57      cpu-migrations            #    0.002 K/sec
+                 1      page-faults               #    0.000 K/sec
+       263,721,559      cycles                    #    0.007 GHz
+       175,746,713      instructions              #    0.67  insn per cycle
+        19,628,798      branches                  #    0.539 M/sec
+         1,259,201      branch-misses             #    6.42% of all branches
+
+       4.549061439 seconds time elapsed
+
+The generated perf-event.pp related policy extension module can be removed
+from the kernel using this command:
+
+   # semodule -X 300 -r my-perf
+
+Alternatively the module can be temporarily disabled and enabled back using
+these two commands:
+
+   # semodule -d my-perf
+   # semodule -e my-perf
+
+If something went wrong
+=======================
+
+To turn SELinux into Permissive mode:
+   # setenforce 0
+
+To fully disable SELinux during kernel boot [3] set kernel command line parameter selinux=0
+
+To remove SELinux labeling from local filesystems:
+   # find / -mount -print0 | xargs -0 setfattr -h -x security.selinux
+
+To fully turn SELinux off a machine set SELINUX=disabled at /etc/selinux/config file and reboot;
+
+Links
+=====
+
+[1] https://download-ib01.fedoraproject.org/pub/fedora/linux/updates/31/Everything/SRPMS/Packages/s/selinux-policy-3.14.4-49.fc31.src.rpm
+[2] https://docs.fedoraproject.org/en-US/Fedora/11/html/Security-Enhanced_Linux/sect-Security-Enhanced_Linux-Working_with_SELinux-Enabling_and_Disabling_SELinux.html
+[3] https://danwalsh.livejournal.com/10972.html
-- 
2.24.1

Re: [PATCH v3 2/3] perf tool: make Perf tool aware of SELinux access control

[Arnaldo Carvalho de Melo]

Em Tue, May 19, 2020 at 10:34:18AM +0300, Alexey Budankov escreveu:
> 
> On 18.05.2020 19:43, Alexey Budankov wrote:
> > 
> > On 18.05.2020 18:58, Arnaldo Carvalho de Melo wrote:
> >> Em Thu, Apr 30, 2020 at 10:15:57AM +0300, Alexey Budankov escreveu:
> >>>
> >>> Implement selinux sysfs check to see the system is in enforcing
> >>> mode and print warning message with pointer to check audit logs.
> >>
> >> There were some changes in this area meanwhile, so I had to apply the
> >> evsel.c by hand, when I push this please double check everything is ok,
> > 
> > Will do. I appreciate your integrating effort.
> 
> Checked at tmp.perf/core branch. The message looks like this:
> 
> [root@nntvtune39 acme.tmp]# tools/perf/perf stat
> Error:
> Access to performance monitoring and observability operations is limited.
> Enforced MAC policy settings (SELinux) can limit access to performance
> monitoring and observability operations. Inspect system audit records for
> more perf_event access control information and adjusting the policy.
> Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open
> access to performance monitoring and observability operations for users
> without CAP_PERFMON or CAP_SYS_ADMIN Linux capability.
> perf_event_paranoid setting is 2:
>   -1: Allow use of (almost) all events by all users
>       Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK
> >= 0: Disallow raw and ftrace function tracepoint access
> >= 1: Disallow CPU event access
> >= 2: Disallow kernel profiling
> To make the adjusted perf_event_paranoid setting permanent preserve it
> in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = <setting>)
> 
> Edited patch at security.txt didn't apply cleanly. It requires white space
> prior tab in the first block for wake_alarm etc till perfmon:

I see, I'll leave it there then so that it applies cleanly to those
policy files.
 
> ---8<---
> diff -Nura a/policy/flask/access_vectors b/policy/flask/access_vectors
> --- a/policy/flask/access_vectors	2020-02-04 18:19:53.000000000 +0300
> +++ b/policy/flask/access_vectors	2020-02-28 23:37:25.000000000 +0300
> @@ -174,6 +174,7 @@
>  	wake_alarm
>  	block_suspend
>  	audit_read
> +	perfmon
>  }
> 
>  #
> @@ -1099,3 +1100,15 @@
> 
>  class xdp_socket
>  inherits socket
> +
> +class perf_event
> +{
> +	open
> +	cpu
> +	kernel
> +	tracepoint
> +	read
> +	write
> +}
> +
> +
> diff -Nura a/policy/flask/security_classes b/policy/flask/security_classes
> --- a/policy/flask/security_classes	2020-02-04 18:19:53.000000000 +0300
> +++ b/policy/flask/security_classes	2020-02-28 21:35:17.000000000 +0300
> @@ -200,4 +200,6 @@
> 
>  class xdp_socket
> 
> +class perf_event
> +
>  # FLASK
> 
> ---8<---
> 
> ~Alexey

-- 

- Arnaldo

Re: [PATCH v3 2/3] perf tool: make Perf tool aware of SELinux access control

[Alexey Budankov]

On 18.05.2020 19:43, Alexey Budankov wrote:
> 
> On 18.05.2020 18:58, Arnaldo Carvalho de Melo wrote:
>> Em Thu, Apr 30, 2020 at 10:15:57AM +0300, Alexey Budankov escreveu:
>>>
>>> Implement selinux sysfs check to see the system is in enforcing
>>> mode and print warning message with pointer to check audit logs.
>>
>> There were some changes in this area meanwhile, so I had to apply the
>> evsel.c by hand, when I push this please double check everything is ok,
> 
> Will do. I appreciate your integrating effort.

Checked at tmp.perf/core branch. The message looks like this:

[root@nntvtune39 acme.tmp]# tools/perf/perf stat
Error:
Access to performance monitoring and observability operations is limited.
Enforced MAC policy settings (SELinux) can limit access to performance
monitoring and observability operations. Inspect system audit records for
more perf_event access control information and adjusting the policy.
Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open
access to performance monitoring and observability operations for users
without CAP_PERFMON or CAP_SYS_ADMIN Linux capability.
perf_event_paranoid setting is 2:
  -1: Allow use of (almost) all events by all users
      Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK
>= 0: Disallow raw and ftrace function tracepoint access
>= 1: Disallow CPU event access
>= 2: Disallow kernel profiling
To make the adjusted perf_event_paranoid setting permanent preserve it
in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = <setting>)

Edited patch at security.txt didn't apply cleanly. It requires white space
prior tab in the first block for wake_alarm etc till perfmon:

---8<---
diff -Nura a/policy/flask/access_vectors b/policy/flask/access_vectors
--- a/policy/flask/access_vectors	2020-02-04 18:19:53.000000000 +0300
+++ b/policy/flask/access_vectors	2020-02-28 23:37:25.000000000 +0300
@@ -174,6 +174,7 @@
 	wake_alarm
 	block_suspend
 	audit_read
+	perfmon
 }

 #
@@ -1099,3 +1100,15 @@

 class xdp_socket
 inherits socket
+
+class perf_event
+{
+	open
+	cpu
+	kernel
+	tracepoint
+	read
+	write
+}
+
+
diff -Nura a/policy/flask/security_classes b/policy/flask/security_classes
--- a/policy/flask/security_classes	2020-02-04 18:19:53.000000000 +0300
+++ b/policy/flask/security_classes	2020-02-28 21:35:17.000000000 +0300
@@ -200,4 +200,6 @@

 class xdp_socket

+class perf_event
+
 # FLASK

---8<---

~Alexey

Re: [PATCH v3 2/3] perf tool: make Perf tool aware of SELinux access control

[Alexey Budankov]

On 18.05.2020 18:58, Arnaldo Carvalho de Melo wrote:
> Em Thu, Apr 30, 2020 at 10:15:57AM +0300, Alexey Budankov escreveu:
>>
>> Implement selinux sysfs check to see the system is in enforcing
>> mode and print warning message with pointer to check audit logs.
> 
> There were some changes in this area meanwhile, so I had to apply the
> evsel.c by hand, when I push this please double check everything is ok,

Will do. I appreciate your integrating effort.

Thanks,
Alexey 

Re: [PATCH v3 2/3] perf tool: make Perf tool aware of SELinux access control

[Arnaldo Carvalho de Melo]

Em Thu, Apr 30, 2020 at 10:15:57AM +0300, Alexey Budankov escreveu:
> 
> Implement selinux sysfs check to see the system is in enforcing
> mode and print warning message with pointer to check audit logs.

There were some changes in this area meanwhile, so I had to apply the
evsel.c by hand, when I push this please double check everything is ok,

- Arnaldo
 
> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
> ---
>  tools/perf/util/cloexec.c |  4 ++--
>  tools/perf/util/evsel.c   | 39 ++++++++++++++++++++++++---------------
>  2 files changed, 26 insertions(+), 17 deletions(-)
> 
> diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
> index a12872f2856a..9c8ec816261b 100644
> --- a/tools/perf/util/cloexec.c
> +++ b/tools/perf/util/cloexec.c
> @@ -65,7 +65,7 @@ static int perf_flag_probe(void)
>  		return 1;
>  	}
>  
> -	WARN_ONCE(err != EINVAL && err != EBUSY,
> +	WARN_ONCE(err != EINVAL && err != EBUSY && err != EACCES,
>  		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
>  		  err, str_error_r(err, sbuf, sizeof(sbuf)));
>  
> @@ -83,7 +83,7 @@ static int perf_flag_probe(void)
>  	if (fd >= 0)
>  		close(fd);
>  
> -	if (WARN_ONCE(fd < 0 && err != EBUSY,
> +	if (WARN_ONCE(fd < 0 && err != EBUSY && err != EACCES,
>  		      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
>  		      err, str_error_r(err, sbuf, sizeof(sbuf))))
>  		return -1;
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 9fa92649adb4..bf437c059c2b 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -2514,32 +2514,41 @@ int perf_evsel__open_strerror(struct evsel *evsel, struct target *target,
>  			      int err, char *msg, size_t size)
>  {
>  	char sbuf[STRERR_BUFSIZE];
> -	int printed = 0;
> +	int printed = 0, enforced = 0;
>  
>  	switch (err) {
>  	case EPERM:
>  	case EACCES:
> +		printed += scnprintf(msg + printed, size - printed,
> +			"Access to performance monitoring and observability operations is limited.\n");
> +
> +		if (!sysfs__read_int("fs/selinux/enforce", &enforced)) {
> +			if (enforced) {
> +				printed += scnprintf(msg + printed, size - printed,
> +					"Enforced MAC policy settings (SELinux) can limit access to performance\n"
> +					"monitoring and observability operations. Inspect system audit records for\n"
> +					"more perf_event access control information and adjusting the policy.\n");
> +			}
> +		}
> +
>  		if (err == EPERM)
> -			printed = scnprintf(msg, size,
> +			printed += scnprintf(msg, size,
>  				"No permission to enable %s event.\n\n",
>  				perf_evsel__name(evsel));
>  
>  		return scnprintf(msg + printed, size - printed,
> -		 "You may not have permission to collect %sstats.\n\n"
> -		 "Consider tweaking /proc/sys/kernel/perf_event_paranoid,\n"
> -		 "which controls use of the performance events system by\n"
> -		 "unprivileged users (without CAP_PERFMON or CAP_SYS_ADMIN).\n\n"
> -		 "The current value is %d:\n\n"
> +		 "Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open\n"
> +		 "access to performance monitoring and observability operations for users\n"
> +		 "without CAP_PERFMON or CAP_SYS_ADMIN Linux capability.\n"
> +		 "perf_event_paranoid setting is %d:\n"
>  		 "  -1: Allow use of (almost) all events by all users\n"
>  		 "      Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK\n"
> -		 ">= 0: Disallow ftrace function tracepoint by users without CAP_PERFMON or CAP_SYS_ADMIN\n"
> -		 "      Disallow raw tracepoint access by users without CAP_SYS_PERFMON or CAP_SYS_ADMIN\n"
> -		 ">= 1: Disallow CPU event access by users without CAP_PERFMON or CAP_SYS_ADMIN\n"
> -		 ">= 2: Disallow kernel profiling by users without CAP_PERFMON or CAP_SYS_ADMIN\n\n"
> -		 "To make this setting permanent, edit /etc/sysctl.conf too, e.g.:\n\n"
> -		 "	kernel.perf_event_paranoid = -1\n" ,
> -				 target->system_wide ? "system-wide " : "",
> -				 perf_event_paranoid());
> +		 ">= 0: Disallow raw and ftrace function tracepoint access\n"
> +		 ">= 1: Disallow CPU event access\n"
> +		 ">= 2: Disallow kernel profiling\n"
> +		 "To make the adjusted perf_event_paranoid setting permanent preserve it\n"
> +		 "in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = <setting>)",
> +		 perf_event_paranoid());
>  	case ENOENT:
>  		return scnprintf(msg, size, "The %s event is not supported.",
>  				 perf_evsel__name(evsel));
> -- 
> 2.24.1
> 
> 

-- 

- Arnaldo

[PATCH v3 2/3] perf tool: make Perf tool aware of SELinux access control

[Alexey Budankov]

Implement selinux sysfs check to see the system is in enforcing
mode and print warning message with pointer to check audit logs.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
---
 tools/perf/util/cloexec.c |  4 ++--
 tools/perf/util/evsel.c   | 39 ++++++++++++++++++++++++---------------
 2 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
index a12872f2856a..9c8ec816261b 100644
--- a/tools/perf/util/cloexec.c
+++ b/tools/perf/util/cloexec.c
@@ -65,7 +65,7 @@ static int perf_flag_probe(void)
 		return 1;
 	}
 
-	WARN_ONCE(err != EINVAL && err != EBUSY,
+	WARN_ONCE(err != EINVAL && err != EBUSY && err != EACCES,
 		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
 		  err, str_error_r(err, sbuf, sizeof(sbuf)));
 
@@ -83,7 +83,7 @@ static int perf_flag_probe(void)
 	if (fd >= 0)
 		close(fd);
 
-	if (WARN_ONCE(fd < 0 && err != EBUSY,
+	if (WARN_ONCE(fd < 0 && err != EBUSY && err != EACCES,
 		      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
 		      err, str_error_r(err, sbuf, sizeof(sbuf))))
 		return -1;
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 9fa92649adb4..bf437c059c2b 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2514,32 +2514,41 @@ int perf_evsel__open_strerror(struct evsel *evsel, struct target *target,
 			      int err, char *msg, size_t size)
 {
 	char sbuf[STRERR_BUFSIZE];
-	int printed = 0;
+	int printed = 0, enforced = 0;
 
 	switch (err) {
 	case EPERM:
 	case EACCES:
+		printed += scnprintf(msg + printed, size - printed,
+			"Access to performance monitoring and observability operations is limited.\n");
+
+		if (!sysfs__read_int("fs/selinux/enforce", &enforced)) {
+			if (enforced) {
+				printed += scnprintf(msg + printed, size - printed,
+					"Enforced MAC policy settings (SELinux) can limit access to performance\n"
+					"monitoring and observability operations. Inspect system audit records for\n"
+					"more perf_event access control information and adjusting the policy.\n");
+			}
+		}
+
 		if (err == EPERM)
-			printed = scnprintf(msg, size,
+			printed += scnprintf(msg, size,
 				"No permission to enable %s event.\n\n",
 				perf_evsel__name(evsel));
 
 		return scnprintf(msg + printed, size - printed,
-		 "You may not have permission to collect %sstats.\n\n"
-		 "Consider tweaking /proc/sys/kernel/perf_event_paranoid,\n"
-		 "which controls use of the performance events system by\n"
-		 "unprivileged users (without CAP_PERFMON or CAP_SYS_ADMIN).\n\n"
-		 "The current value is %d:\n\n"
+		 "Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open\n"
+		 "access to performance monitoring and observability operations for users\n"
+		 "without CAP_PERFMON or CAP_SYS_ADMIN Linux capability.\n"
+		 "perf_event_paranoid setting is %d:\n"
 		 "  -1: Allow use of (almost) all events by all users\n"
 		 "      Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK\n"
-		 ">= 0: Disallow ftrace function tracepoint by users without CAP_PERFMON or CAP_SYS_ADMIN\n"
-		 "      Disallow raw tracepoint access by users without CAP_SYS_PERFMON or CAP_SYS_ADMIN\n"
-		 ">= 1: Disallow CPU event access by users without CAP_PERFMON or CAP_SYS_ADMIN\n"
-		 ">= 2: Disallow kernel profiling by users without CAP_PERFMON or CAP_SYS_ADMIN\n\n"
-		 "To make this setting permanent, edit /etc/sysctl.conf too, e.g.:\n\n"
-		 "	kernel.perf_event_paranoid = -1\n" ,
-				 target->system_wide ? "system-wide " : "",
-				 perf_event_paranoid());
+		 ">= 0: Disallow raw and ftrace function tracepoint access\n"
+		 ">= 1: Disallow CPU event access\n"
+		 ">= 2: Disallow kernel profiling\n"
+		 "To make the adjusted perf_event_paranoid setting permanent preserve it\n"
+		 "in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = <setting>)",
+		 perf_event_paranoid());
 	case ENOENT:
 		return scnprintf(msg, size, "The %s event is not supported.",
 				 perf_evsel__name(evsel));
-- 
2.24.1