[v1,1/3] capabilities: introduce CAP_SYS_PERFMON to kernel and user space

Commit Message

Alexey Budankov Dec. 5, 2019, 4:19 p.m. UTC

Introduce CAP_SYS_PERFMON capability dedicated to secure performance
monitoring activity so that CAP_SYS_PERFMON would assist CAP_SYS_ADMIN
capability in its governing role for perf_events based performance
monitoring of a system.

CAP_SYS_PERFMON aims to harden system security and integrity during
performance monitoring by decreasing attack surface that is available
to CAP_SYS_ADMIN privileged processes.

CAP_SYS_PERFMON aims to take over CAP_SYS_ADMIN credentials related to
performance monitoring functionality of perf_events and balance amount of
CAP_SYS_ADMIN credentials in accordance with the recommendations provided in
the man page for CAP_SYS_ADMIN [3]: "Note: this capability is overloaded;
see Notes to kernel developers, below."

Signed-off-by: Alexey Budankov <[e-mail]>
---
 include/uapi/linux/capability.h     | 10 +++++++++-
 security/selinux/include/classmap.h |  4 ++--
 2 files changed, 11 insertions(+), 3 deletions(-)

Patch

diff --git a/include/uapi/linux/capability.h b/include/uapi/linux/capability.h
index 240fdb9a60f6..c9514f034be1 100644
--- a/include/uapi/linux/capability.h
+++ b/include/uapi/linux/capability.h
@@ -366,8 +366,16 @@  struct vfs_ns_cap_data {
 
 #define CAP_AUDIT_READ		37
 
+/*
+ * Allow usage of perf_event_open() syscall (perf_events subsystem):
+ * http://man7.org/linux/man-pages/man2/perf_event_open.2.html
+ * beyond the scope permitted by perf_event_paranoid kernel setting.
+ * See Documentation/admin-guide/perf-security.rst for more information.
+ */
+
+#define CAP_SYS_PERFMON		38
 
-#define CAP_LAST_CAP         CAP_AUDIT_READ
+#define CAP_LAST_CAP         CAP_SYS_PERFMON
 
 #define cap_valid(x) ((x) >= 0 && (x) <= CAP_LAST_CAP)
 
diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index 7db24855e12d..bae602c623b0 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -27,9 +27,9 @@ 
 	    "audit_control", "setfcap"
 
 #define COMMON_CAP2_PERMS  "mac_override", "mac_admin", "syslog", \
-		"wake_alarm", "block_suspend", "audit_read"
+		"wake_alarm", "block_suspend", "audit_read", "sys_perfmon"
 
-#if CAP_LAST_CAP > CAP_AUDIT_READ
+#if CAP_LAST_CAP > CAP_SYS_PERFMON
 #error New capability defined, please update COMMON_CAP2_PERMS.
 #endif